Devastation in Temecula - 11/99
Glassy-Winged Sharpshooter Hammering Wine Grapes
By Patrick Cavanaugh
It's glassy, it's winged, and it's cutting like a knife in Temecula, Calif. winegrape vineyards.
The Glassy Winged Sharp Shooter (GWSS) is a newer pest to Southern California and in three short years in transmitting Pierce's Disease has all but devastated the 3,000 acres of winegrapes growing in the Temecula winegrape region. Experts worry that the millions in losses there could easily translate to billions in losses to the rest of California vineyards and other crops when it begins to spread northward.
Already, confirmed sightings have been made in Kern County, San Joaquin counties and there are fears that if populations build unchecked, then a repeat of Temecula could be in the cards for these areas.
With no effective control strategy in sight, there is real fear that GWSS will spread throughout the agriculture-rich San Joaquin Valley, threatening nearly 800,000 acres of table, rain and wine grapes-72 percent of the state's vineyards-with deadly Pierce's disease-which clogs the water-conducting tissue of plants causing the plants to wither away.
Almond growers could be drastically effected as well with the insect vectoring almond leaf scorch.
Among the most heavily affected vineyards in Temecula is Temecula Valley Vineyards, (TVV) a 500 acre winegrape operation producing Chardonnay, Cabernet, Nebbiolo and Sangiovese.
TVV owner, Roberto Ponte, is also the President of the Temecula Wine Grape Association. "We started having problems on a 20 acre Chardonnay vineyard that I was managing in 1996. Two years later, we had to take the vineyard out," said Ponte. "We also saw some of our own vines dying in 1996, which were right next door to the vineyard we had to remove."
"Because of the symptoms, we thought the problem may have been Pierce's disease," said Ponte. "I started sweeping for blue green sharpshooter that year and I didn't find a single one."
"When I started seeing hundreds of vines dying we contacted University of California researchers and because there was no budget to study the problem the growers of the area decided to assess ourselves $12.50 per acre to help find out what was going on. Money was raised and Dr. Matthew Blua, a Post-Doctoral Research Associate at UC Riverside was dispatched to Temecula. Blua placed some sticky traps out and that's when GWSS was discovered in the vines.
In 1997, damage began increasing in great numbers and has grown exponentially over the past two years.
Today, GWSS is affecting nearly every vineyard block in the Temecula region, killing a combined 500 acres to date, Ponte said, adding, yields are down significantly due to the damage. "The 10-year average Chardonnay yields have been six tons per acre. This year we only had about two tons per acre," Ponte said.
Temecula's largest winery, Callaway Vineyard has been hard hit as well-losing more than 40 acres.
The problem is so dire in Temecula that the city of Temecula has given $125,000 to fight the pest. The Riverside County Board of Supervisors matched the city with another $125,000 and the State of California has earmarked $2,250,000 over the next three years to combat the problem.
Contingency plans are already in place in other major grape production regions.
Monterey County Grape Growers Association recently held an emergency meeting in mid-October in response to what is happening in Temecula. The group formed the Central Coast Pierce's Disease Task Force. Chairman of the task force is Corky Roche, of Roche Vineyard Consulting, based in Salinas.
Roche has made trips to Temecula to see firsthand the disease pressure. "What we saw was shocking," Roche said. "Of the 3,000 acres of wine grapes in the valley, the majority of the blocks are showing major Pierce's Disease symptoms. In the next two years, it is expected that all vineyards in the area will be infected."
"We are working closely with the ag commissioner's office and with UC Cooperative Extension farm advisors on our task force goals which are three-fold. 1) To educate the industry and the public as to the threat of the GWSS; 2) To monitor (with traps) for the GWSS at areas that may have had the pest imported; and 3) to attempt to reclassify the pest as a Category "B" pest. (An example of an "A" pest would be the medfly). What a "B" classification does is allow the county to establish controls and or quarantine measures in the county.
Currently, GWSS is a "C" pest which means there is no urgent need for the state to step in and combat its spread.
Scientists concur that California has a serious problem. "The spread of glassy-winged sharpshooter throughout the state's grape-growing regions represents what I believe is the most serious threat ever to California viticulture," said Sandy Purcell, UC Berkeley Professor of Entomology.
"GWSS and the diseases it vectors are possibly two of the greatest threats ever to California agriculture," said Richard Redak, UC Riverside, Associate Professor, Department of Entomology. "If nothing is done, it will certainly lead to disaster in Temecula."
"If we push hard and keep it from spreading, then we can save ourselves," said Roche. "We don't want to become complacent and think the state will protect the industry when in reality, we could lose the industry."
Roche echoes what other experts feel, that the GWSS threat is unprecedented in the history of viticulture in California. "It's a threat to all growers and we should all be contacting our ag commissioners and farm advisors and asking them what is being done about this pest and disease complex."
Roche said Monterey county has already implemented trapping for GWSS. "We need state-wide trapping," Roche said. "We don't want a situation where the pest can establish itself in residential areas forcing the industry to spray those areas."
Monterey County is focusing its trapping at retail and wholesale nurseries where it could be receiving plant materials from infected areas of the state. "If something major doesn't break in terms of curative in the next two years, then the industry will not survive in Temecula," Roche warned.
The pest was accidentally introduced into Southern California from the Southeast U.S. as eggs on nursery stock . It was first observed in Ventura county in 1990. The insect has been recorded to feed on more than 70 species of plants in 35 different plant families and is active throughout the year.
To feed, GWSS uses piercing mouth parts to tap into the water conducting tissues of its host plants and consumes the water and nutrients that it finds. The major threat that the insect poses is that it transmits a deadly plant bacterial pathogen, Xylella fastidiosa. Different strains of this bacterium induce diseases in many agricultural and ornamental plants, including almonds, peaches, plums, alfalfa, and citrus.
Phil Phillips, area IPM Advisor based in Ventura County said the initial discovery of GWSS was in 1990 on eucalyptus windbreaks in Ventura County and a lemon grove near Santa Paula. Today the pest is well established in the coastal region citrus groves. Pest control advisers in the area report that they are so numerous in the trees that it feels like there is a misting rain overhead when walking beside the trees. The GWSS is such a voracious sucking insect and hungry for nutrients that its excrement is like a fine white-wash on the leaves.
On citrus, egg masses may be laid in fruit rind-making the fruit unmarketable. Many Ventura-area growers have experienced a decrease in pack-out due to rind injury.
The GWSS is far different than the more common blue-green, green or red-headed sharpshooter that has for years aggravated grape growers near riparian zones. And while GWSS still spreads Pierce's disease, it does it faster, more widespread and is much more difficult to control.
Purcell said GWSS threatens to worsen Pierce's disease in several ways, due to its increased number of vectors, and faster and longer movements into vineyards. Also, its breeding habitats and different crop host preferences as well as its desire to feed on larger (basal) stems leads to exponential disease increases compared to other sharpshooters.
It's much larger, it flies further and is certainly in greater numbers into commercial agricultural plantings than our native sharpshooters, Purcell noted.
Ponte described a multi-pronged approach in terms of preserving the future in Temecula. "The first thing is to kill the bug which is difficult due to its flying behavior. Provado (imidaclorpid) can kill the sharpshooter, but probably not fast enough to prevent it from transmitting the bacteria that causes diseases.
Work is also being done in releasing egg parasitoids as a biological control technique that may reduce and limit GWSS populations in citrus and grapes as well as urban areas within Southern California.
Research to determine if the bacterium responsible for Pierce's disease can be prevented by boosting a grapevines' level of essential plant micronutrients, such as zinc, iron and molybdenum. It has been established in the laboratory that certain concentrations of these micronutrients are toxic to bacteria. What is needed is to develop a system that gets those nutrients in the grapevine to protect it from infection.
Injecting antibiotics into the grapevine is being explored, but the work is long-term and may not yield results in time for Temecula.
For sure, genetic work won't come in time . But genetics are a long-term approach to Pierce's disease prevention. Muscadine grapes, native to the southeastern U.S. are poor for making wine, but they are resistant to Pierce's disease. Perhaps the resistant gene or genes could be transferred into California's vinifera grapes.
"Assuming positive results can be brought to bear on the situation in Temecula in time, in my opinion, is questionable," said Redak. "However, to do nothing will certainly lead to disaster in Temecula."
Reducing Spread of GWSS - 4/00
Major Ag Counties Step up Prevention Programs
By Patrick Cavanaugh
Wide spread efforts throughout California's key agricultural production areas are in place to prevent the spread of Glassy-winged Sharpshooter (GWSS), the more fierce and deadly vector of Pierces Disease on grapes, which causes additional fatal disease on other major commodities.
GWSS has been detected in and apparently infests the counties of Kern, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara and Ventura.
As of mid-March, 10 other counties are requiring that shipments of GWSS-host plant material from infested counties to be shipped under the Blue Tag protocol. The restriction holds the plant material for inspection by the destination county's Agricultural Commissioner's office. Ultimately, the Blue Tag will effect more than 100 host plants, most of them ornamentals and heavily shipped throughout the Spring. So far, the counties enforcing the Blue Tag restriction are: Alameda, Contra Costa, Fresno, Lake, Mendocino, Monterey, Napa, San Joaquin, Sonoma and Tulare.
What happens if the inspector detects GWSS? The load is rejected and must be reloaded on the truck and transported out of the county back to the sender, or to another county not requiring Blue Tag protocol and only with the permission of the new destination county.
"The key is to get as many counties as possible on the Blue Tag program so that the infested load does not find a home," said Corky Roche, a vineyard consultant in Monterey County.
There is also work being done to initiate a change in the pest rating of GWSS from the current C-rating to a B-rating. "It's really ridiculous that we need to deal with this pest on the receiving end," said Roche, who is also chairman of the Monterey County-based Central Coast Pierces Disease Task Force, the most active of the several County-based task forces set up to deal with the threat. "The sender of the nursery stock should insure that it does not harbor the pest."
Eric Lauritzen, Monterey County agricultural commissioner, said the B-rating would upgrade the standard of cleanliness, to "Free From," (a pest) at the nursery level if the plants were destined to move outside the county. "This makes much more sense," said Roche. "We would ultimately like to see it as an A-rated pest, which is the rating of the Medfly. Not only does an A-rating require that a shipment be free from medfly, it also requires eradication whereever it is found."
Both the Nursery Growers Association (NGA) and California Association of Nurserymen (CAN) have both been eager to help with the Blue Tag program. "They have endorsed the Voluntary Compliance Agreement for their members," said Roche. "Their help has been crucial; however, although these organizations represent the majority of the nursery acreage in the infested areas, they do not represent the majority of the growers. This leaves the Ag Commissioners in these areas to urge nonmember growers to control the pest, if infested, when shipping to the north."
In Temecula where the GWSS has nearly devastated the vineyards of the wine grape industry, work is being done to stem the damage. Citrus growers have received a Section 18 for Admire through drip, which systemically take the material up into the tree where the GWSS may be feeding. "This will hopefully knock back the overwintering populations of GWSS for this season," said Roche.
But there is not much being done regarding the hundreds of additional overwintering plants such as residential areas and municipal landscaped areas.
To further protective measures, Monterey and Napa Counties are ready to push forward with local ordinances that will require inspection at sites in infested counties before any agricultural products can be shipped, particularly grapevines. "This needs CDFA approval and may take a few months, but it looks good," said Roche. "There have been many shipments of wine grape vines coming form the Temecula area into San Benito County, but arrangements have been made for this to stop."
While Monterey County has been on the forefront of the GWSS issue, it has helped that Lauritzen, besides being the agricultural commissioner, is also president of the California Association of Ag Commissioners and Sealers. Lauritzen has been making numerous trips throughout the state discussing the concerns about GWSS and he recently hosted a meeting in Monterey with 30 county agricultural commissioners, primarily discussing ways to prevent the spread of the pest.
"This is not an effort to merely prevent the spread of GWSS into Monterey," said Lauritzen. "It is part of a huge effort to prevent it spreading to any area in California where it doesn't exist. It is a collaborative approach with other agricultural commissioners, the nursery industry, CDFA and other related industries. Everything is voluntary at this point."
It is interesting that in Santa Barbara County, where the pest was identified nearly 10 years ago on the southern end of the county, there has never been a significant increase in GWSS numbers and it has never been found in the county's huge wine region to the north. There is speculation that cool, year-round temperatures keep GWSS populations low. In areas with hot summers, such as the Central San Joaquin Valley, the pest may certainly gain faster momentum, like it did in Temecula.
And what is the latest on two major agricultural counties in the San Joaquin Valley where GWSS was discovered last season?
Jack Marks, deputy agricultural commissioner in Kern County where GWSS has been present in what seems to be a small population for two years, said they are keeping a close vigil. "It was originally found in eucalyptus trees in the Edison area," said Marks. "We're trying to determine if it's growing in population and how far it has moved from that original source, if it has moved at all."
"There are so many unanswered question," Marks said.
One GWSS bug was also found in San Joaquin County in a Lodi apple orchard in September. Vicki Helmar, assistant county agricultural commissioner said it was found in an apple maggot trap. "At that time, we increased the trap density in the area and also surveyed the orchard and a nearby vineyard with sweep nets and beating trays and did not find any additional sign of GWSS. This past February, when it was thought overwintering adults would be out laying eggs; another visual inspection took place, again finding no sign. "We suppose that it was simply a lone hitchhiker."
"We will be surveying and trapping all nursery stock coming from infested areas," said Helmar. There will also be significant trapping in citrus, vineyards, as well as Prunus species which includes almonds, cherries, peaches and plums, all major host plants to GWSS.
In San Joaquin County, a local GWSS task force is meeting regularly discussing both preventive and mitigation measures.
In Napa County, assistant agricultural commissioner Fred Crowder said numerous measures are in place to track and prevent GWSS's spread. Besides utilizing the Blue Tag protocol, the county is implementing intense survey programs. "We have put traps in all commercial nurseries as well as other high hazard pest detection sites such as near Medfly traps throughout Napa County and we're also doing visual inspections with sweep net and beating trays in vineyards.
"If we do find the bug we will then immediately treat the area and then try and determine how widespread it is in the county," said Crowder. "We are also requesting growers who are purchasing green-growing wine grape vines from counties known to have GWSS to treat the vines with Admire."
In Napa County, the Glassy-winged Action team is working diligently to also educate homeowners about the threat of GWSS. Crowder said a lot of nursery stock is brought from the south to the north by unsuspecting homeowners which could lead to a huge problem.
Crowder is pleased to see that many surrounding Bay Area counties are enforcing the Blue Tag restriction. "This should be a major help to prevent the spread of GWSS in the area," said Crowder. "We are going to watch the situation very close this summer."
In the meantime, there seems to be a lot of GWSS denial throughout the industry, noted Roche. "A lot of people see the action coming out of Monterey and other counties and don't think they need to get involved," he said. "And there is also a big sector of the industry that feels this is not a threat to them."
"It's critical that when we are treating for the pest in vineyards that we also treat the adjacent host plants as well, whether its citrus, almonds or even neighborhoods, which is going to be a tough sell," said Roche.
"Once you get to the point that exists in Temecula, an area surrounded by infested crops and ornamental plants, it's a devastating situation," Roche said. "Everything we are doing now is to prevent that situation from repeating itself here in the north."
By Theresa Oliveira, Assistant Editor
It's been raising quite a stir throughout the state and for good reason. It's none other than the notorious glassy-winged sharpshooter, which spreads Pierce's disease to a number of crops, particularly grapes. This is great concern to grape growers statewide. Many are leading local or county task forces to help keep the pest at bay. Among the most active task forces is San Joaquin County, which is comprised of about 25 to 30 people, mostly grape growers.
With just-released survey guidelines from the California Department of Food and Agriculture to follow, San Joaquin County Agriculture Commissioner Scott Hudson is leading the task force along with the county Farm Bureau. According to Hudson, growers in San Joaquin County have taken a proactive approach in preventing the glassy-winged sharpshooter from infiltrating the region.
San Joaquin County has become a leading grape growing region in the state and growers intend to keep it that way. For this reason, the county's glassy-winged sharpshooter task force is an active one focusing on survey and detection. Ag Commissioner Hudson explained that grape growers have taken the lead in the task force, but other commodity producers also serve on the committee.
"Grape growers are taking the lead because we're familiar with Pierce's Disease," said John Ledbetter of Vino Farms, Inc. in Lodi, Calif. "We're a little more attuned to it." Ledbetter who farms in a number of counties throughout the region said not every county necessarily needs a task force, but rather they can work together.
He noted a number of people from both Sacramento and Stanislaus Counties have attended San Joaquin's task force meetings. He said the idea is to not keep it a secret if a glassy-winged sharpshooter is found in your vineyard, orchard, yard, etc., but rather report it to the county ag commissioner. It's important to report such an incident so the proper steps in preventing it from spreading can be taken.
Ledbetter along with Brad Lange of LangeTwins Vineyard Management Company, Inc., Cliff Ohmart, Ph.D. Research/IPM Director with the Lodi-Woodbridge Winegrape Commission and San Joaquin Ag Commissioner Scott Hudson, are working extensively on this issue. They are striving to educate growers and the public about the glassy-winged sharpshooter so more people will know what to look for and how to detect it.
The sharpshooter, which is prevalent in the southern region of the state, has as grape growers know infiltrated much of the area's grape growing region. Growers throughout California have seen the devastation left behind by the glassy-winged sharpshooter in the form of Pierce's Disease. This is all the incentive San Joaquin grape growers needed to take a stance to prevent this from occurring in their county. "We have personal acquaintances in Temecula," said Brad Lange. "We know how devastating it can be."
One of the task force's concerns is the fact that much of the area's ornamental plants are grown and shipped from Southern California where the glassy-winged sharpshooter has a strong presence. "This is a multi-commodity problem affecting citrus, peaches, almonds, alfalfa, grapes and other crops," said Ag Commissioner Hudson. "The pest is also found in nurseries. This is especially important because of the high risk involved from ornamentals traveling up and down the state."
Hudson informed one of the first steps in the control and prevention program in San Joaquin County is traps, that will be dispersed throughout the county. Similar efforts are being taken by other county task forces on the North Coast, Central Coast and in the Valley. "If we find the glassy-winged sharpshooter in small pockets then that is where we need to set up the control," said Cliff Ohmart. "The control won't hurt the crop, in fact it may help."
According to Ohmart, the traps and the vineyards themselves should be monitored weekly, if not daily. Employees such as tractor drivers, irrigators, foremen, etc. also need to know what the glassy-winged sharpshooter looks like. Ohmart mentioned there is nothing really to attract the sharpshooter to the traps other than the fact that they are sticky.
The commonly seen bright yellow sticky traps are the type being used to help monitor this pest. Traps should be changed at least every two weeks. It is not known at this time if there is a pheromone or scent that can be placed on the traps to attract the glassy-winged sharpshooter. At the moment it is more of a hit-and-miss situation where the pest can be caught in the trap while in flight or blown to the trap by wind.
Aside from the traps and visual detection the San Joaquin County Glassy-winged Sharpshooter Task Force is putting up posters with the picture of this pest throughout the county. Their goal is to let everyone know what the pest looks like and who to contact if one is found. A total of 4000 posters have been printed with 2000 printed in Spanish.
According to Hudson, help from the community has been supportive in the task force's plight. Funds gathered from industry members will be put into a trust to be used as needed. Hudson is also anticipating support on both the state and federal level. The County Board of Supervisors has also stepped in at the request for emergency funding. "It's a cooperative effort between counties, the state and federal government." Hudson is one of the county ag commissioners representing the Valley on the State Task Force. He said with two-thirds of the state's grape population grown in the Valley from Kern to Sacramento, the glassy-winged sharpshooter issue is a big concern.
Last fall a glassy-winged sharpshooter was found in San Joaquin County, but not in a vineyard. Since that time no others have been found. But the task force isn't taking any chances. "We're going the extra mile to make sure San Joaquin County is glassy-winged sharpshooter free and remains free," stated Hudson.
A Serious New Vector Threatening to Increase Disease
Pressure in California's Grape and Almond Industries
One thing California doesn't need is another pest in agriculture or the urban landscape. However, the glassy-winged sharpshooter, Homalodisca coagulata Say (Homoptera: Cicadellidae), fits the bill on both counts. Likely introduced around 1990 on nursery stock from the southeastern United States, where it is a known agricultural pest vectoring several bacterial diseases, this insect was first observed as a novelty on eucalyptus windbreaks in Ventura County lemon orchards near Santa Paula.
By 1992 adults were observed on the stems of young lemon trees. In 1993 the first egg masses were observed in lemon tree foliage by this author. Adults were collected in the early spring of 1994 and sent to Jerry Davidson, entomologist with the Santa Barbara County agricultural commissioner's office. Formal identification was made by Dr. Ray Gill, CDFA.
The glassy-winged sharpshooter (GWSS) is a large insect (-0.5 inch) whose general color is brown to black when viewed from the side or above. The underside of the abdomen is whitish. The upper aspect of the head and thorax are brown or black with numerous ivory to yellowish spots. These spots allow this sharpshooter to be easily distinguished from one of its close relatives in southern California, the native smoke tree sharpshooter (H. lacerta Fowler), which has pale, wavy lines instead of the spots.
Since the early 1990s, this insect has proceeded to expand its numbers and its range to where it can now be found in many southern California counties. It has recently been found in the lower San Joaquin Valley in Kern County.
This insect has rapidly gone from novelty status to potentially a very serious pest. Sharpshooters are xylem tissue sap-feeders, generally accessing the water conductive xylem tissue of their host plant through the stem or major leaf veins using their strong stylet-like piercing mouthparts. As xylem feeders, sharpshooters as a group can be effective vectors of bacterial plant pathogens, particularly the xylem-limited bacterium Xylella fastidiosa. Once injected by the sharpshooter vector into the plant's xylem tissues, this bacterium multiplies and produces a gel-like material that in combination with the multiplying bacteria blocks the water conductive xylem tissue.
This initially causes die-back of leaves and shoots distal to the point of infection and eventually causes the entire plant (e.g. grape vines) to collapse and die within a year or two (several years for mature citrus, peach or other trees) as the infection becomes systemic. Pierce's disease of grapes, almond leaf scorch, phoney peach disease in the southern U.S., variegated chlorosis of citrus (Brazil), and most recently oleander leaf scorch in southern California are all caused by various strains of Xylella fastidiosa. It is the first two diseases that are of immediate concern to California's grape and almond industries, both caused by the same strain of this bacterium.
The GWSS has had a long association with Pierce's disease of grape in the southeastern U.S. as a vector of the causal bacterium. Its current impact on the Temecula Valley wine industry of Southern California due to the recent dramatic increase in the incidence of PD there has caused great concern regarding this insect's migration from southern California northward into vineyards and almond orchards of the Central Valley as well as into coastal vineyards. The same strain of the bacterium causes both PD and almond leaf scorch.
Unlike the current sharpshooter vectors associated with Pierce's disease or almond leaf scorch here in California (blue-green, green and red-headed), the GWSS is much larger, has a much broader host range and flies much further and certainly in greater numbers into commercial agricultural plantings than our native sharpshooters.
Unlike our native sharpshooters, it can breed in many tree fruits as well as grapes. The ease with which GWSS moves into the middle of agricultural plantings extends the threat of PD infections from primarily a vineyard boarder problem to a vineyard-wide problem, even on the largest plantings, as is the current case in some Temecula vineyards.
Populations of GWSS have already moved into some Kern County vineyards and citrus orchards. It is likely already in yet unknown locations further north. Because of its wide host plant range, the GWSS is not confined to riparian areas. It can easily develop large populations on dooryard ash, eucalyptus, macadamia, or stone fruit trees. Areas with native laurel sumac and commercial citrus also harbor large populations of GWSS.
The large numbers this insect germinates in crop or non-crop plantings increases the likelihood of bacterial transmission from even the smallest source, even though its transmission efficiency is less than some native sharpshooters.
On Glassy Wings They Come - 6/00
Pierce's Disease an Agricultural Nightmare
By Darl Larsen, Associate Editor
Meet the "super vector." It eats, it breeds, it flies. It kills.
Reminiscent of the respect/awe/fear for the "perfect eating machine" described by the character Hooper in the movie "Jaws," this "super vector" may be a sort of vineyard great white, and California's agricultural bounty its defenseless, unwitting prey.
If the glassy-winged sharpshooter (Homalodisca coagulata) weren't such a downright serious menace, you just might be impressed by it. It can transmit the Xylella fastidiosa bacterium-which causes Pierce's disease (PD)-to not only grapevines, but, according to the California Department of Food and Agriculture, can transmit corresponding diseases to a wide variety of California agriculture staples: oleander, almonds, tree fruits, ornamentals and alfalfa, and on. Its "super vector" status is assured by its size, insatiability and flying acumen-abilities that allow for a more rapid and effective transmission of the disease.
Recently, it has become difficult to avoid the topic. Newspapers up and down the state have carried sometimes daily, front-page coverage of the looming threat. Like the insidious fruit flies of years past, this new pest causes fear and concern wherever it appears. And that "wherever" seems to be spreading rapidly. Originally confined to southern California, the glassy-winged sharpshooter has been found in the southern San Joaquin Valley (Kern and Tulare counties), and eggs have been shipped northward, into Madera and perhaps even Fresno County and beyond into wine country. The CDFA has heard the calls from growers and extension personnel statewide and turned its attention to this latest threat to California's multi-billion dollar ag industry. As a result, the glassy-winged sharpshooter (GWSS) has been officially upgraded from a "C" rated pest to a "B" rated pest, which means that CDFA can inspect all nursery stock coming from the eight southern California counties, looking for sharpshooters or its egg masses.
Target counties (free of GWSS but in receipt of nursery shipments from infected counties) like Napa, Sonoma, Lake, Mendocino and those in the Bay Area have implemented "blue tag" policies. All shipments coming from infected nurseries in southern California counties must be blue-tagged for immediate inspection in the north by Ag Commissioner staff. Compliance agreements in infected counties also exist to ensure that all shipments have been inspected before transport. These are in lieu of inspection at the receiving end. Napa County, though, does not honor the compliance agreements, and inspects every incoming shipment. Egg masses-some viable-have been found as a result of these inspections, and the plants were either treated or rejected entirely.
So just what is this flying phantom menace? Worse than the Medfly, which could destroy a crop, Pierce's disease kills the vine itself, destroying any future crop. The bacterium in question, Xylella fastidiosa, causes Pierce's disease, and in the 1960s was most often found in or near alfalfa fields, causing alfalfa dwarf. X. fastidiosa can be carried in the gut of the now infamous GWSS, a half-inch long leafhopper pest, which spreads the bacterium in the simple act of feeding. The GWSS punctures the stems of grapevines to reach the sap inside, infecting the canes. According to CDFA, the GWSS is also a prodigious consumer of liquid. To keep itself alive it takes in the "equivalent of a 150-pound human drinking 4,300 gallons of liquid a day." Much of this liquid is processed and then excreted as the GWSS feeds, reducing the host plant's photosynthetic abilities and marring its appearance and growth.
Inside the plant, the X. fastidiosa bacteria multiply, effectively blocking the water and nutrient flow. The infected plant then starves. Many plants are merely impaired with the bacteria, but those severely infected will eventually die. Riverside County alone has already lost more than 500 acres and nearly $4 million; the Temecula Valley has lost $6 million since 1997.
The GWSS is a super vector in comparison to another pest, the blue-green sharpshooter leafhopper (BGSS). Both are vectors of Pierce's disease (PD), but the BGSS is far more benign than the GWSS. The BGSS tends to feed close to the edges of vineyards and at the tips of shoots. Consequently, most new infections can be trimmed out each year with proper pruning, and the bulk of the vineyard remains untouched by the pest. Not so with the GWSS, which is much larger, flies further, and feeds at the base of vines, rendering even careful pruning insufficient.
Pierce's disease has become a well-known threat to northern California vineyards (since 1995), and has more recently (1997) attacked vineyards in the Temecula Valley in southern California. The disease affects wine, raisin and table grapes, not just one variety, and has a strong foothold in Riverside, San Diego, San Bernardino, Ventura, Santa Barbara, Los Angeles, Orange and Kern counties. In Kern County, for instance, "isolated infections" of PD have been found in the Shafter area and east of Earlimart, according to Mario Viveros and Don Luvisi, Kern County Cooperative Extension personnel. Both GWSS and PD are present in the county, but an epidemic infection has been avoided to date. GWSS has also been found in the Lamont area, and both Viveros and Luvisi see it as "only a matter of time" before GWSS meets PD and the grapevine feeding truly begins. The citrus groves of Tulare County and the vineyards of Fresno and Madera counties aren't much farther north.
Treatments to date are limited, at best. Local spraying with insecticides can be effective only on a local basis. Infestations mean something much more sinister. Treatment questions remain, such as do we fight the insect or the bacteria? Growers and state personnel are talking about erecting "fire walls" around infected areas such as Porterville and Arvin-Edison to contain the spread of the disease. The chemical/biological fire walls might take care of the natural advancement of the disease and the vector, but won't do much to stop truck-borne pests.
And the wheels are turning elsewhere, too. The State Senate in SB 671 has appropriated $6.9 million to create the Pierce's Disease Control Program within CDFA, and the Governor has signed the bill. That amount will be matched for the 2000/2001 fiscal year, for a current total of $13.8 million in direct state funds dedicated to this disease. The Governor has appointed Bob Wynn as the program's interim coordinator. Two other proposals have been forwarded at the State Senate level. SB 1445 will "exempt from property tax reassessment the replanting of grapevines that have been stricken with Phylloxera or Pierce's Disease," and AB 1790 would match the previous exemptions as well as "allow for changes in variety and density of the new plantings." Final decisions are pending on these new pieces of significant legislation.
At the federal level, the Agriculture Risk Protection Act (HR 2559) passed in the House, with the help of Rep. George Radanovich (R-Mariposa). The act includes $7.14 million in funds for USDA to fight PD during this fiscal year.
"Our productive agricultural region could soon be in peril," Radanovich said. "Allowed to progress unchecked, the effect of Pierce's disease will be tragic, particularly to vineyards. Thousands of acres of grapes have already been eradicated in the Temecula area of our state as a result of the GWSS."
A grape grower himself, Radanovich may be particularly sensitive to this potential blight. Grapes continue to be California's largest crop, and ranks as the sixth largest crop in the nation. Producing over 90 percent of the nation's grapes, California and the nation can ill-afford the immense losses this disease portends.
The Agricultural Research Service (ARS) in association with Brazilian scientists has recently announced that it was focusing on Pierce's disease, as well. The ARS and scientists from Brazil's Organization for Nucleotide Sequencing and Analysis in the Virtual Genomics Institute are looking for the gene sequence of the Xylella strain-specifically the strain affecting the Temecula Valley vines. Once the gene composition is known, they will seek a way to fight it, to short circuit it. Brazilian researchers have already had success sequencing a Xylella strain that affects citrus varieties. A gene that controls virulence, for example, can perhaps be targeted once the mapping is complete.
ARS plans to contribute $125,000 to the effort. The American Vineyard Foundation and CDFA will each contribute $62,500, and the state of Sao Paulo Research Foundation (funding the genome research) has earmarked $250,000. ARS scientists are also looking for repellents and insecticides to combat the sharpshooter, as well as beneficial insects and "other organisms" to attack the pest. In Tulare County, they're already talking about parasitic wasps and the like.
Counties that could stand to lose everything should grapes becomes infected-like Napa County in northern California-are taking proactive steps to combat the disease. The cooperative extension in Napa County has recently contacted its growers to announce a countywide monitoring program for GWSS, even though GWSS has not yet appeared in the county. The goals of the program are twofold: to document that Napa County is currently free of GWSS, and that any new infestations be located and eradicated. Photos and online information regarding GWSS adults, nymphs and eggs are being made available to anyone interested, and "suspicious insects" are asked to be taken to the cooperative extension office for identification. Log onto www.malcolmmedia.com for complete GWSS updates and links to other important sites. Information is also being made available in Spanish.
Established populations of GWSS don't happen overnight, and the occurrence of a single specimen can be anomalous, according to Ed Weber, Viticulture Farm Advisor, Napa County. Rogue insects can easily hitch rides on trucks without being able to establish infestations in GWSS-free counties. Vigilance becomes the key term, and monitoring the principal action.
Yellow sticky traps can be used to monitor GWSS, though no trap has been found to be highly effective, since pheromone-laced traps and lures don't exist for GWSS. The traps should be placed in vineyards near any type of landscaping or other vegetation, in open flight areas and not hidden in canopies, and especially near recently landscaped areas. The homestead islands in the midst of acres of vines or groves act as jumping-off points for new GWSS infestations, and should be monitored carefully. GWSS are known to travel on plants from southern California, commercial ornamental and otherwise, on green-growing grape plants from infected nurseries (most likely in southern California), and in truckloads of harvested fruit from southern California.
Another potential arrow in the quiver for the agriculture industry in the fight against PD is chemical. The EPA recently approved a Section 18 on Admire 2 Flowable Insecticide from Bayer for use on citrus, an alternate host for GWSS. Both the California Association of Winegrape Growers (CAWG) and the California Citrus Quality Council (CCQC) have been working with the EPA toward Admire approval. The USDA ARS has funded Admire treatments (along with other products) on citrus groves in the search for GWSS control.
According to Bayer, Admire will be ground-drenched for citrus application, with its active ingredient, imidacloprid, working systemically through the root systems to control GWSS multiple life cycles. The collateral benefit to adjacent vineyards and orchards should be apparent. Long term results are pending. Lorsban and Dursban are also possibilities for treating individual plants (in backyards, for example, though home use of Dursban may soon be illegal) to kill the insects themselves, but this would only work if an infestation level has not been reached.
A kaolin clay spray is also being trialed as a possible treatment, a repellent, of sorts. As a result, acres of ghostly white grapevines now cover Temecula's rolling hills.
As with any agricultural dilemma, though, knowledge may well be the best hedge against future disaster. Knowing the disease, how to identify its presence, and keeping abreast of the latest treatment regimens are going to make all the difference. According to the Napa County Cooperative Extension, GWSS has a list of "preferred plants for feeding and/or egg laying," which could prove helpful to the vineyard owner and homeowner alike: citrus, crepe myrtle, privet, photinia, camellia, ash, sycamore, magnolia, peach, sunflower, hollyhock, malva (a weed), sow thistle (a weed), and lambsquarters (a weed). A complete list of preferred plants is available online through www.malcolmmedia.com.
The latest reports of viable egg masses are unfortunately coming from northern California. GWSS eggs were discovered by routine inspection in a Home Depot garden center in Rohnert Park (Sonoma County, California) on ornamentals from infected southern California nurseries; similar finds were recently made in Marin and Contra Costa counties, also on ornamentals from southern California. The infected plants were stripped and sent back to their origination sites. The GWSS's northward march is underway, and seemingly being facilitated by the agriculture community's own transportation system.
Living, feeding sharpshooters are now known to be infesting areas of Porterville in Tulare County, where a $443 million grape industry is centered. PD has been around for years in Tulare County, but not the super vector GWSS. Factor in the added element of trying to fight a pest that lives in backyards just as happily as vineyards, and the monumental task ahead becomes clear. Door-to-door searches are now underway in the Porterville area, believed to be the first such search undertaken. According to Bill Peacock, Tulare County farm advisor, the fact that Thompson grapes (used for both raisin and table grapes throughout the Central Valley) are less susceptible to PD than other varieties may help the county's growers and grape industry. The same cannot be said for wine grapes, of course. Additional trappers are being added in Tulare, Fresno and Madera counties, with GWSS eggs recently appearing on ornamentals in Madera County which probably originated in Ventura County.
Fresno County's grape industry produced $605 million in 1999; Madera County produced an additional $229 million. More and more, the similarities between the Temecula Valley-devastated by Pierce's disease-and both Fresno and Madera counties are being voiced. All three counties share similar conditions for the worst possible GWSS infestations-including and especially proximity between citrus groves and vineyards. The very heart of California agriculture is threatened as the Central Valley counties become the next likely GWSS targets.
Everyone involved seems to remember the 1880s Pierce's disease blight that destroyed 40,000 acres of Anaheim-area vineyards and closed more than 50 area wineries. Temecula wants to head off such a catastrophe, though growers may feel like they're bailing with a sieve. The San Joaquin Valley and the wine-producing counties may be the stage for the next series of confrontations. "In this corner, the Super Vector." The winner? That's the billion(s) dollar question.
Taking Steps to Stop GWSS
By Darl Larsen, Associate Editor
At the most recent Central Coast Viticulture and Enology Issues Conference held in Santa Maria, California, the subject of the menacing glassy-winged sharpshooter (GWSS) was addressed.
Phil A. Phillips, Area IPM Advisor, UCCE Ventura County, spoke on the fight against Pierce's disease (PD) and its most accomplished vector, GWSS.
Phillips noted first that protecting a vineyard from infestation, or at least delaying that infestation, stands as the "first line of defense." Keeping the GWSS out of productive grape areas is now a top priority in the entire state. Harvested grapes from other infected areas or just vehicles coming from known host counties need to be identified and dealt with, while landscape nursery stock (ornamentals) from similarly infected counties-including most counties in southern California, as well as Kern County in the south Valley-destined for plantings near or around vineyards and homesteads should be turned away. Proximity is the key-proximity between the vector and the target. The farther apart you can keep one from the other, the better.
Planting border "trap crops" around vineyards is suggested to create a sort of "moat" idea or outer wall surrounding the vineyard. If your vineyard is your inner castle with all the goods, then there must be barriers around that castle. Phillips suggests traps like an early and vigorous (thus attractive to GWSS) grape variety, or even young lemon trees that might provide the necessary slowdown of the GWSS needed to attack it. The GWSS should be attracted to these trap crops earlier in the season, and then should be vulnerable to repeated applications of insecticide (on the trap crops), and may keep them from moving beyond the "outer wall" and into the vineyard.
If the vineyard in question happens to be located next to or near citrus groves, Phillips suggests more innovative approaches. In the Temecula Valley area, where millions of dollars of GWSS damage has affected thousands of vineyard acres, some vineyard owners are getting positively proactive. Many have leased the citrus groves bordering their vineyards, thus wresting control of the vector (as GWSS tends to harbor in citrus trees) and attacking the GWSS with repeated contact insecticide applications in the citrus grove. Again, the key here is stopping the GWSS before it even leaves its host environment.
Inside-the-vineyard GWSS management is another consideration entirely. Recent infestations have indicated that the speed at which GWSS moves and its effective transmission of X. fastidiosa bacterium make in-progress control difficult. Phillips calls the challenge "near heroic." The GWSS is at home in the vineyard and will breed there, as well. Even if used repeatedly, the "short-lived contact pesticides" seem to leave what Phillips calls "windows of opportunity" where GWSS can quickly reestablish itself, and continue feeding. The long-lived systemic insecticides-imidacloprid-like Admire from Bayer Corporation, suppresses GWSS populations for weeks at a time, but with a curious twist. Phillips notes a 1999 lemon orchard study wherein an imidacloprid treatment resulted in a nearly 95 percent reduction in GWSS activity for up to 10 weeks. The twist is this: Evidence seems to support that GWSS weren't actually killed by the insecticide outright, but simply avoided the treated trees and plots, clumped themselves into untreated trees and plots, and continued to feed. Those caged insects which were sprayed in treated trees didn't die immediately, either, but significantly reduced their feeding until death by starvation and/or dehydration occurred more than a week later.
In another "similarly treated vineyard" in the Ojai area in 1999, the insects continued to feed even after treatment for more than a week. This feeding activity and duration depended on how quickly after treatment the GWSS were exposed to treated vines. Those insects placed in sleeve cages on treated vines exhibited reduced feeding activity as compared to those insects caged on untreated vines. Transmission of the bacterium X. fastidiosa (carried in the gut of GWSS) in these feedings may or may not have occurred. Four bioassays at "successively greater intervals" were conducted posttreatment, and exposure at the greater intervals "resulted in longer survival times before death ensued, presumably from starvation and/or dehydration," Phillips concludes. Those insects that were held in the canopy but not allowed access to canes (their primary feeding targets) all died within either 48 or 96 hours of the bioassays, held during warmer and cooler weather, respectively.
Another, perhaps more sobering research project conducted by the University of Georgia between 1995 and 1997 and using only imidacloprid applications failed to protect the test vineyard from complete infestation. An 18-month delay from the onset of the PD infection to the entire vineyard being infected was accomplished, but a 100 percent infection rate was recorded. In this Georgia study, GWSS was the main culprit vector, as well.
Phillips seems to conclude that though the news seems grim, there are avenues of response. He reminds that the test plots in the Georgia study were decidedly small and under "considerable vector feeding pressure," which the normal vineyard may never experience.
"Vector pressure along with bacterial inoculum sources from outside the vineyard is a critical factor in the success of disease prevention programs within the vineyard," Phillips said.
The treatment strategies for Pierce's disease and its most efficient vector, the glassy-winged sharpshooter, can't be put off until the vineyard in question is under attack. Careful vigilance, including trapping, as well as monitoring of canes, will keep the grower up-to-date on his vineyard's health.
Becoming proactive-especially when the vineyard borders a citrus grove or where a "trap crop" can feasibly be installed-might make the difference between a pest that can be fought and a disease that just destroys.
The California grape industry continues to battle Pierce's disease, a destructive disease of grapevines. The bacterium that causes Pierce's disease (PD), Xylella fastidiosa, is spread by a small group of insects that feed on the xylem tissue of grapevines. PD kills grapevines, especially young vines, by interfering with water transport through the vine. While the southern portion of the state tackles a new threat from the recently introduced glassy-winged sharpshooter, winegrape growers in the North Coast continue to fight the spread of the disease that has plagued them for years.
In the North Coast, the bacterium that causes PD is spread by native insects, most commonly the blue-green sharpshooter. PD first appeared in Southern California grapevines in the 1880s where it destroyed the vineyard industry in some areas. Over the next 120 years PD has slowly spread to where it is now found as far north as Mendocino County. By the 1940s PD was first found in Napa County and by the late 1940s had begun to show up in Sonoma County. Napa still bears the brunt of PD damage in the North Coast, but the impacted acreage in the area increases each year.
The insects that spread the disease live in landscape plants, riparian vegetation and hillside vegetation in the winter months. During the spring and summer, they feed on grapevines spreading the bacteria they have picked up from other plants. Many of the plants commonly found along the edges of vineyards, as well as yards and gardens, carry the bacteria. Often these plants do not show any symptoms and can be reservoirs for the disease for many years.
Once infected, grapevines are quick to succumb to the disease. Symptoms first appear as stunted shoots and brightly colored leaves. As the disease progresses, the fruit dries up and leaves begin to fall off. The symptoms, particularly early ones, are often confused with other diseases, nutritional problems, or even lack of water. However, there are distinctive symptoms to confirm the disease as well as laboratory tests that can detect the bacteria. If the cause is Pierce's disease, the vine dies within one to two years.
In response to the growing impact of the disease, growers and wineries in the North Coast formed the North Coast Pierce's Disease task force (NCPDTF) in 1994. The goal of the task force is to fund research and promote farming practices to reduce Pierce's disease. The NCPDTF has raised hundreds of thousands of dollars and with the cooperation of the American Vineyard Foundation (AVF) has increased PD research from near nothing to a major research effort at universities all across the country.
One continuing program of the task force is to survey grape growers to understand the financial aspects of the disease and gather growers' opinions on management practices that might be beneficial. In 1999, the survey obtained responses from over 400 growers representing well over 40 percent of all the planted grape acreage in the North Coast. Napa County was particularly well represented with nearly 60 percent of the planted acreage being covered by respondents. Financial impacts have been extrapolated to all growers in the three counties, with the assumption that non-respondents to the survey are affected to the same degree as respondents. This may or may not be true, but the high response rate increases the confidence of the extrapolations.
There are some 8,300 acres of vineyard currently infected with PD in the North Coast. About 17 percent of Napa County acreage have some PD, compared to 8 percent of Sonoma County grape acres. Over the last five years, 775 acres in the North Coast have been replanted due to PD, of which 670 acres were in Napa County. The cost of replanting the 775 acres, including lost crop during replanting, was over $33 million or nearly $6.6 million/year for each of the five years. An additional 563 acres have been removed from production and not replanted due to PD, with 523 of those acres being in Napa County. The value of that land is estimated at $27.5 million.
In terms of direct losses, North Coast growers lost nearly 5,100 tons of grapes in 1999 alone (81 percent from Napa) at a cost of over $10.5 million. Additionally, growers actually spent nearly $1.2 million on PD control measures. These PD control measures include traps, insecticides, and vegetation control, but not the costs associated with replanting vines lost to PD.
Overall, PD losses and direct costs totaled $46 million in the three counties. This includes both direct expenditures and losses due to decreased crop production and land taken out of production.
But growers are not giving up. A number of management alternatives are being implemented by North Coast growers. The use of insecticides is one control measure commonly used. Two-thirds of Napa growers, about one-half of Sonoma growers and one-third of Mendocino growers used insecticides inside their vineyard last year. A little less than one-half of growers in all three counties used insecticides outside the vineyard for PD control. While insecticides can be effective, growers are sensitive to their impact on the environment. As a result, most growers use insecticides that selectively target the harmful insects as opposed to broad range insecticides.
North Coast vineyard operators continue to search for new ways to deal with Pierce's disease while maintaining a healthy environment. One result of these grower-funded research efforts has been the implementation of selective habitat modification along vineyard borders. Managing the vegetation outside the vineyard is a commonly used method for the control of PD. By removing plants that serve as hosts for the sharpshooter and/or the Xylella bacterium, it may be possible to reduce the spread of the disease. Close to 80 percent of growers responding to the survey have done vegetation management outside the vineyard. Vegetation management primarily involves removing host plants such as Himalayan blackberry, periwinkle, and wild grape. Since the idea of removing vegetation, which provides habitat for wildlife and beneficial insects, is unattractive to growers and the public, over one-third of North Coast growers are going further by replanting the areas around their vineyard with new vegetation. The replacement planting is usually with California native plants that provide similar wildlife and fishery habitat values, yet have been shown not to harbor the disease. Even more growers intend to restore vegetation outside their vineyards in the future.
Winegrape growers in the North Coast have until recently been the major source of funding for PD research. That research has lead to improved testing methods along with a number of management practices to deal with the disease, while reducing the use of broad-spectrum pesticides. Current work by the NCPDTF and other groups is continuing to elucidate the host range of the disease and its vector, especially with respect to ornamental plants. University cooperators are exploring opportunities to develop PD-resistant winegrape varieties and are testing bactericidal systems that might rid vines of the disease after infection. Experience has shown that single pest control strategies eventually fail. Pierce's disease, like all vineyard pest problems, will require a multifaceted management approach. The NCPDTF and its cooperators will continue to work toward a comprehensive, sustainable management program. NCPDTF wishes to thank all of the growers who took the time to return their survey and provide us with valuable information in the battle against Pierce's disease. For more information on this survey contact Dr. Don Clark at Nord Coast Vineyard Service in Napa, CA.
The Battle Rages On
By Darl Larsen, Associate Editor
In American Vineyard's continuing efforts to keep readers informed, these pages will feature monthly updates on the glassy-winged sharpshooter (GWSS) situation in California's agricultural heartland.
Recently, significant events have occurred in the identification, assessment, and planned treatments of GWSS in California. More California counties have joined the ever-growing list of GWSS finds, including Contra Costa County, specifically the city of San Ramon, where three adults were found in late June. In San Joaquin County adult GWSS were found in Lodi, Linden and Tracy. Lodi is, of course, the center of the enormously significant Lodi-Woodbridge wine grape area. New finds were made in nurseries in Reedley (Fresno County) in late June, and in Porterville (Tulare County) in the first week of July.
In June USDA Secretary Dan Glickman announced a declared agricultural emergency in California, which will ultimately provide $22.3 million in federal assistance. This is a direct response to the threat posed to the California grape industry by Pierce's disease and its most capable vector, GWSS. Recommended restrictions on bulk grapes are also in place, allowing GWSS-free counties to more strictly control grape imports from known infected counties.
Napa County has even declared that it will take steps to completely prohibit the importation of any grape and/or nursery stock from infested counties. This establishes, in essence, a quarantined area, but this must be approved-under state law-by William Lyons, Jr., secretary of the state Department of Food and Agriculture. Napa County is seeking to protect its vital wine industry-an industry that could be wiped out if the GWSS reaches the region's vineyards.
On the command-and-control front, it's been announced that researchers at UC Riverside are studying a centuries-old defense strategy: the physical barricade. And while some would agree with poet Robert Frost that "good fences make good neighbors," GWSS are known to fly at fairly low levels, often below 15 feet, thus the idea of erecting 15 to 18-foot tall fences between GWSS habitats (such as orange groves) and preferred feeding areas like vineyards. The fences are actually tall mesh screens capable of stopping a flying GWSS. High sticky traps were deployed in a test area, waiting for venturing sharpshooters.
Early "barricade" results are promising, according to Matthew Blua of UC Riverside: "We caught around 95 percent of them flying at or below 15 to 18 feet."
The mesh fences won't be cheap, though. They're usually only used for protection in the cut-flower industry and with other "pricey" crops. California's grape industry certainly falls into that category now.
Mesh fences laced with insecticides are also being considered, a stratagem meant to kill the insects, not just deter them. Sticky traps are also under consideration.
Also being studied are various parasitic wasps. Wasps are known exploiters, devouring the organs and fluids of other insects. Wasps can hatch from nests of weaker insects, and they can nest on other insects, as well. The wasp gonatocerus ashmeadi hunts out sharpshooter eggs and lays its own eggs in the sharpshooter egg mass. When the wasp eggs incubate, the host mass is destroyed. Another, larger wasp, pseneo punctatus, attacks adult sharpshooters, stinging and paralyzing them. The wasp then buries the sharpshooter in the ground and lays its eggs on it. The end result is more wasps, and fewer mature GWSS.
These biological controls are being studied by researchers in the hopes that mass releases of wasps can soon be accomplished. Currently, such research is being centered in the devastated Temecula Valley region in Riverside County, where the grape industry has so far taken a $6 million hit.
Of the half-dozen parasitic wasp species that attack GWSS egg masses, only one has been found that tolerates California's climate. A species of Mexican wasp is also being studied since it is already adapted to the arid West Coast climate. UC Riverside officials say the earliest planned release of wasps will be in August.
The ultimate goal in cutting edge research, however, isn't killing the GWSS, but finding ways to make grapevines more resistant to Pierce's disease. Research is underway to develop such varieties, but is probably years from fruition. Scientists see three "promising" areas of Pierce's disease control: plants injected with antibiotics, spraying plants with a zinc and copper solution, and exploiting naturally occurring bacteria as grapevine strengtheners.
At the more immediate level, work continues, as well. Fresno and Madera counties have increased trapping in ever-wider areas, with unfortunate success. More GWSS finds are being reported, and in areas further from riparian environments. In the Sunnyside district of Fresno, multiple GWSS discoveries were made in early June. This followed discoveries in the San Joaquin River border areas between Fresno and Madera counties. A "Fresno County Glassy-Winged Sharpshooter Task Force" is in place, taking calls from residents who think they find the culprits in their yards. Often they're right. Sunnyside is now an infestation area.
Fresno County entomologist Norman Smith calls the GWSS finds "fairly prevalent," noting that on his first inspection it took just 10 minutes to find a nymph. Smith is fairly certain that the GWSS have come into the county on nursery stock from infested counties in Southern California.
Door-to-door canvassing for GWSS has been implemented by members of the California Conservation Corps, and continues in several parts of Fresno County.
More recently, the effects of insect infestation have begun reaching beyond county borders. The state announced in mid-June that both Fresno and Tulare counties would have to begin strict examinations of any exported nursery stock and grape concentrate. These examinations would serve to prove that the products were free from GWSS infestation.
This move adds these counties to the long list of southern California counties already under similar stringent requirements. Local officials are concerned, of course, that such a requirement creates a pariah status for any infected county. The order also affects the nearly 2,000 grape growers in Fresno and Tulare counties who grew more than half of all the wine grapes crushed in California in 1999. Add to that the approximately $150 million in grape concentrate, and the numbers become sobering.
Nat DiBiduo of Allied Grape Growers is alarmed about the far-reaching effects of this harvest time dilemma: "My concern is that what if the county remains infested come harvest time. Some of the proposals for moving bulk grapes from an infested county to an uninfested county are just onerous."
Some counties, like Napa County, may even decide to refuse any shipments from an infested county, whether the incoming shipment is clean or not. The compliance agreement paperwork alone could be mountainous.
Also in the here-and-now are ongoing chemical treatments. Carbaryl (Sevin) is being sprayed in Tulare County and in the Sunnyside area of Fresno. Spraying began within a 9-square mile area in Porterville June 20-21, where numerous GWSS finds have been made. This is a house-by-house spray regimen, with homeowners alerted as to the spray times and the chemical used. Tulare County expected to treat a total of about 230 properties in the first round of spraying, but that number grew to more than 320 by early July. Residents in Tulare County continued to call in GWSS finds, and crews continued to be dispatched. Treatments began July 1 in San Joaquin County. In Fresno County's Sunnyside area, spraying began June 27, and the first round ended July 3. Residents were being educated as to the dangers of such spraying, and were being advised to cover yard toys and tools, ornaments and furniture. Spray crews were covering items in yards if homeowners did not. All spray areas will be carefully monitored before, during and after treatments by Department of Pesticide Regulation (DPR) personnel.
And since the sprays don't kill egg masses, a second round of spraying will most likely be necessary. The general interim between sprays is two to four weeks, depending on hatching. Carbaryl (Sevin) is also relatively safe for humans, laboratory tests have shown, and has a wide application rate across a broad range of plants. One drawback might be carbaryl's effectiveness against beneficials, as well, including honeybees, ladybird beetles, predacious mites and aquatic insects. Some ornamentals are also sensitive to the spray.
Newer hotspots include the Peach-Alluvial and the Fresno-Shaw areas of northeast Fresno and Clovis. A door-to-door search was undertaken in the Peach-Alluvial area, with more than 60 properties found hosting the GWSS, and more than 20 in the Fresno-Shaw area. An informational meeting was held for the Peach-Alluvial residents on July 6. Spraying in the Peach-Alluvial area began in the second week of July.
These treatments and the searches that prompt them have led to other disturbing finds in Valley agriculture. Red imported fire ants continue to plague Madera County almond orchards, and olive fruit flies are being discovered in the Porterville area, near Kingsburg, in Madera County and in the Fresno High area of Fresno. More than 50 fruit flies have been trapped from across Tulare County, and 43 of those were confirmed as the insidious olive fruit fly, the most dangerous olive insect pest. Tulare County officials are fanning out with more traps and pesticide applications.
The question that looms large now is the specter of the wine grape harvest. Fresno County Ag Commissioner Jerry Prieto poses the question: "Can we move wine grapes out of this county?" With some counties already hinting that any incoming grapes must be crushed, the difficulties become obvious. Are there facilities in place in Fresno County to handle such an order? Are there enough trucks to ship the crushed grapes? The threat of transporting GWSS and Pierce's disease in bulk grapes might be enough to slam shut the doors to many still-uninfested counties.
An early indication of just such a possibility came recently from Mexico, where Mexican authorities hastily closed their borders to California apricot trucks in an attempt to keep out unwanted pests, in this case the peach twig borer, the oblique banded leafroller and the orange tortrix. The border was reopened after a tense few days, though prices dropped as growers and handlers scrambled to find buyers elsewhere. It will be apparent very quickly whether the same uncertainties face the California grape industry.
The battle between man and insect continues
Stay with American Vineyard magazine and visit our website, www.malcolmmedia.com, for continuing coverage of California's agricultural pest battles.
By Dan Clarke
Once it was called Anaheim Disease. It's also been known as The Mysterious Disease and The Vine Disease. It virtually eliminated agriculture in the Los Angeles Basin in the 1880s. Pierce's Disease (Xylella fastidiosa) has always been a problem for California vineyardists, but never such an urgent one until recently.
Pierce's Disease (PD) is now borne by its most aggressive vector, an import from the Southeastern United States, the glassy-winged sharpshooter (Homalodisca coagulata). Its cousins, the more benign blue-green, red-headed and green sharpshooters have been in California longer. The blue-green variety is common along the coastal areas and lives along riverbanks. In the Central Valley the red-headed sharpshooter is found on grasses, especially Bermuda grass but does not like grapes. The green sharpshooter does carry the PD bacterium in the Central Valley but its damage is usually limited to an edge effect along the outside of vineyards, much as the blue-green variety does in Napa.
Amador County growers may not ever see the glassy-winged sharpshooter (GWSS) in their Sierra Foothill vineyards, but they're taking steps to prepare for it. In early June they gathered in the 19th century Shenandoah Schoolhouse near Plymouth to meet with Alexander H. Purcell, a University of California, Berkeley professor who for years was the country's only entomologist working on this disease. Dr. Purcell toured a number of the area's vineyards during the day and addressed the topic with area growers later that afternoon before joining a large group of growers for a lamb barbecue.
Ray Ryan, President of the Amador County Grape Growers Association, who convened the meeting expressed a cautious optimism. "We don't fit the profile (of the GWSS favored environment), but insects are insects," he said. "They're highly adaptable and it raises some concern. We're hoping that it can't winter over at this elevation. Most of Amador County's vineyards are at 1500 feet and above. Our biggest problem (ordinarily) happens to be frost damage."
In traditional infestations of Pierce's Disease, the progression is more-or-less linear, according to Purcell, advancing annually from one, to four, to six percent of the vineyard. He cited a chilling example of a Southern California vineyard in which the disease was transmitted by the glassy-winged sharpshooter: "In 1997 the vineyardist pulled out three vines. The next year he pulled 100. Last year it was over 1,000. There's no hope today of eradicating this insect in California, but what we're trying to do is slow the progress."
Purcell explained that April and May "are the months when vines are most susceptible. In tests, infections that start later in the year are more likely to be pruned out over the following winter. The samples inoculated near the base of the cane have much greater chance of sustaining the disease than those plants inoculated near the tip of the cane. (In major infestations) severe pruning is the remedy, but if the symptoms of PD are very slight, my advice is to leave it alone. Normal pruning may get rid of it."
Part of the reason the glassy-winged sharpshooter is such an effective vector of the disease is that it feeds at the base of the cane and it feeds on stems of dormant, woody plants. It also occurs in habitats not previously used by PD vectors such as citrus trees. Two major habitats are citrus and irrigated ornamental landscapes, neither of which is a common sight in the county, and Purcell offered the opinion that if the GWSS were to become a threat in Amador County it would be in areas by streams or by irrigated landscapes. "I don't think this is the environment the glassy-winged sharpshooter will thrive in," said Purcell, "but there's a lot of uncertainty in that statement.
A concerned grower asked the predictable question, "What can we do to mitigate our situation?" Purcell's reply was to install and check sticky traps and to "keep your eyes open for this glassy-winged sharpshooter which excretes a lot of water. If you see or feel a lot of drops coming from a tree, look up for the (GWSS)." The grower followed with the inquiry, "Do we go after the host, the vector or the disease?" "Yes!" was the professor's resounding response, "I don't mean to make light of the situation, but all three must be addressed." Dick Cooper, a long-time area grower, asked Purcell to play seer and describe what the association's Pierce's Disease meeting would be like four years hence. "No one really knows," offered Purcell. "The experts can tell you you're not going to have a problem . . . but I don't really know. I'd say I don't think you're going to have a problem-or if you do, it'll be a very localized one. But that's an expert opinion . . . and I really don't know!"
Note: links to websites with information on the GWSS are available at www.malcolmmedia.comGG
By Darl Larsen, Associate Editor
The battle against the glassy-winged sharpshooter and Pierce's disease has fallen from the front pages of most major newspapers, like the stories it originally replaced. But that's what happens to news items, our attention spans being what they are. You've now got to track down GWSS-related articles and briefs in "business" or "local" sections.
Unfortunately, the effective Pierce's disease (PD) vector-the glassy-winged sharpshooter-hasn't gotten the message that it's become yesterday's news. Recent spraying treatments in Alameda, Fresno, Tulare, Sacramento (Rancho Cordova), Santa Clara, San Joaquin and Stanislaus counties attest to the perilous constancy of the GWSS and PD struggle.
In our continuing efforts to keep readers up-to-date, American Vineyard offers another roundup of the recent and current GWSS- and PD-associated engagements in California.
Add Stanislaus County to the growing list of GWSS finds, as a single adult male was recently discovered in the first week of August at a wholesale nursery in west Modesto. It's hoped the lone insect was a "hitchhiker," just one clinging to a nursery delivery, rather than having been hatched in the area. Treatments are underway, and trap monitoring continues.
Follow-up trapping and examination of other nursery stock have uncovered no new finds in Stanislaus County. Any level of infestation, though, means the county has a lot to lose, according to Hughson-based Duarte Nursery owner John Duarte.
"Stanislaus County is the biggest agricultural nursery county in the state," Duarte said. "We can't afford to let the populations get larger or spread. It's worth every cent we are spending right now."
Another nursery, this one at the southern end of the Valley in Kern County, has been protecting its interests now for a long time.
Sunridge Nursery's production manager Steve Maniaci says Sunridge has instituted a "zero tolerance" policy in regard to either letting sharpshooters in or shipping them out of their huge nursery.
"We decided the best way to protect ourselves was to practice complete exclusion," Maniaci said. "We covered every greenhouse and shade house with insect screen to keep the bugs physically out. Then we used chemical controls as a backup."
"We physically inspect every vine that leaves here. We hired extra people and set it up so it wouldn't impact plant movement. We're determined to deliver on time and GWSS-free."
A Kern County Ag Commissioner representative also inspects shipments daily.
Maniaci concludes: "By practicing exclusion, we've suffered zero losses and zero finds on our crops. The worst thing that could happen to us would be to ship one plant with one bug on it. We simply won't allow that to happen."
Elsewhere, most of Sacramento County will be happily declared pest-free after weeks of vineyard examinations that have turned up no infestations. Only a nine-square-mile section of non-vineyard area in Sacramento County was found to have GWSS, and spraying was undertaken there.
In other news of proactivity, the announcement of the imminent release of parasitic wasps (Gonatacerus triguttatus) in Tulare, Fresno and Kings counties stands as one of the opening biological salvos against GWSS in the Central Valley. These wasps are from Mexico, and are considered more effective than local predators because they lay their eggs in the unhatched sharpshooter eggs. The sharpshooters are then killed before they can hatch and do any agricultural damage.
The wasps are being quarantined at UC Riverside, and should have earned California Department of Food and Agriculture (CDFA) approval for release in August. The quarantine is necessary to determine whether the wasp will prove more damaging in the long run due to unforeseen collateral effects. Small-scale releases on a trial basis were scheduled for late August in Tulare County.
"We don't see [the parasitic wasp] eating plants, damaging insects that are not sharpshooters or stinging humans or others," said UC Riverside biological control specialist Mark Hoddle.
Growers and counties are already clamoring for the wasps, according to Larry Bezark, head of CDFA's biocontrol program. The wasps will be released a little at a time in particular areas, and could be repeated as needed.
California's native parasitic wasp, G. ashmeadi, kills sharpshooters very well which will hatch in the summers-with up to a 90 percent effectiveness-but is much less deadly when put up against those pests which will hatch in the spring. This spring deficit is what the imported wasp is meant to address. Two other wasps, both non-native, are also in quarantine and also under research for possible biocontrol release.
This wasp release program is part of the state's "rapid response" plan for Fresno, Tulare and Sacramento counties, and is being readied for implementation, if necessary, in any other California county.
"The rapid response plan is ready to roll, if needed, in other counties," said CDFA Secretary William J. Lyons, Jr. "The counties already operating under the plan have helped us fine tune it. We appreciate their commitment to controlling the glassy-winged sharpshooter."
To date, approximately $36 million has been earmarked for the battle against GWSS and PD in the state.
These attempts at biological controls are important, especially when the specter of widespread and expensive spraying is considered. Spraying kills living, feeding sharpshooters but isn't being considered as an eradication measure, especially since infestation levels have been reached in many hot spots. Sprays are being used as "knock down" agents, reducing populations of adults.
In news of recent finds, Terra Bella (Tulare County) and Kingsburg (Tulare/Fresno County) have been identified as the some of the newest GWSS infestation areas. The Terra Bella find occurred in late June and marked the second community in Tulare County to be identified as home to glassy-winged sharpshooters. The number of properties found to host GWSS in Tulare County has nearly reached one thousand, with most of those in the Porterville area.
Centered near the Conejo Avenue offramp of Highway 99, the Kingsburg find is all the more disturbing because of its central location in the multibillion dollar San Joaquin Valley grape industry, according to Bob Vandergon, assistant agricultural commissioner for Fresno County. Door-to-door searches were immediately implemented in the residential areas of the find.
Approximately 30 properties in the Kingsburg area, including parts of the Highway 99 right-of-way, have been found to be infested.
This last find coincided with the beginning of the bulk grape shipments in California. Grape growers had worried that tagged shipments would be met with stiff opposition, but have been assured by the state that shipments cannot be refused simply because they are tagged, nor can lower prices be given by virtue of the shipment's origin. Yellow tags festooned shipments from and within infested residential regions (within a mile of an infested area), while green tags adorned those shipments from uninfested regions. Thus far, there have been very few GWSS finds in commercial vineyards, specifically Sunnyside and Biola.
Packaged raisins and table grapes are not being tagged.
Recent GWSS finds in the cities of Madera, Rancho Cordova (near Sacramento), and in southeast Fresno (near DeWitt and Barstow avenues) have kept local officials on their toes as they broaden delimitation areas, struggling to find the outermost limits of the infestations.
Other recent finds include: the cities of Sunol and Fremont (Alameda County), where adult glassy-winged sharpshooters were trapped in a nursery in each city; Middletown (Lake County) where one adult GWSS was found in a nursery; Galt (Sacramento County), where three adult GWSS were trapped in a nursery; Lodi, Linden, and Tracy (San Joaquin County), where adults continue to be found in at least four separate nurseries; Portola Valley (Santa Clara County), where one adult was trapped in a nursery; and Orange Cove (Tulare County), where one adult was trapped in a citrus grove.
All of the above areas were immediately defined as areas of possible infestation, and delimitation steps were undertaken.
The number of infested properties already identified in Fresno alone has risen past 300.
In Fresno County recently, the California Conservation Corps announced that it had doubled-from 40 to 80-the number of its personnel assigned to the area to assist agricultural commissioner staff members. Another 15 CCC personnel are working in Tulare County, also performing door-to-door legwork and pest identification.
And as the first batch of spraying regimens wound down in the Central Valley, attention turned to just how effective Sevin had been in controlling the GWSS population in residential areas.
University of California entomology farm advisor for Fresno Richard Coviello asked as early as July 3 whether or not the spraying had knocked down the pest. With other grape advisers and entomologists he visited a property in Sunnyside where spraying had just taken place. They found "live adults and even nymphs pretty much all over the plantings that had been sprayed two days earlier," according to Coviello. Questions about the pest's ability to hide above its imaginary 15-foot flight ceiling came up, as did the reminder that the spraying was being used as just the first round of treatment.
County officials had hoped for an 80 to 85 percent effectiveness from the Sevin sprays, which means spraying won't be the ultimate solution. The next battlegrounds seem to be fomenting in the laboratory and the greenhouse.
"We're trying to slow the spread [by spraying] to give the researchers time," said Patrick Gleeson, executive director of the American Vineyard Foundation, "but the only way we're going to be able to solve the problem in the long term is to focus on the bacterium."
Scientists believe that development of a Xylella-resistant, high-quality grape is at least 10 years down the road. Andrew Walker, UC Davis, is searching for just such a species. His research looks at hundreds of grape DNA samples for the combinations which would generate both a disease-resistant and world-class grape.
Other researchers are looking instead at the DNA of the bacterium itself, Xylella fastidiosa. Brazilian researchers are currently mapping the Pierce's disease strain of X. fastidiosa, looking to develop an antibiotic to kill the bacteria which causes PD. Until that time, scientists, government personnel, and growers must rely on limited control measures to keep GWSS at least in check.
Pierce's disease and GWSS have assumed premier positions in grower- and industry-related publications and gatherings. Sun-Maid's recent field day was transformed from a Mite Day into a sort of GWSS-information day. With GWSS finds in Fresno, Tulare, Kern and Madera counties, and especially with the latest finds in Sun-Maid's backyard (Kingsburg), it's no surprise that the raisin giant has joined the fray.
Various county viticulture newsletters and communiqués from ag commissioners' offices also continue to put GWSS in the spotlight.
CDFA announced in late July the implementation of strict emergency regulations for the PD Control Program, and applicable to any grape grower in an identified infested county. Compliance agreements were demanded from any grower in Sacramento, Fresno, Tulare, Kern, Santa Barbara, Ventura, Los Angeles, Orange, San Bernardino, Riverside and San Diego counties prior to the movement of bulk grapes.
This compliance agreement included a 72-hour preharvest notification to the local Ag Commissioner, information about shipping destinations, and the obtaining of compliance certificate tags. The stated purpose of the compliance agreements was the prevention of the "artificial movement of the glassy-winged sharpshooter into non-infested areas while facilitating the efficient movement of grapes to crush."
Absence of the pest means these rules wouldn't apply to that region's shipments.
And if the glassy-winged sharpshooter weren't prolific enough, UC Cooperative Extension entomology farm advisor Richard Coviello noted recently that the pest could also spread a serious disease of peaches, plums and nectarines. "Phony peach disease" isn't known to be in the Central Valley (it is commonly found in the southeastern U.S.), but if there's a vector that has the ability to rapidly spread the bacteria in California, GWSS is the one.
Coviello notes that phony peach disease ultimately reduces the infected tree's ability to produce fruit by as much as 80 percent, with the only current treatment being removal of the tree.
Vine mealy bug finds in the Central Valley are reminding growers that when it rains it pours. This pest excretes a substance onto grape bunches, and can cost growers as much as $80 an acre for treatment.
The vine mealy bug has been in the U.S. for about six years, and instead of flying from vineyard to vineyard, hitches rides on equipment, clothing, etc.
For the latest glassy-winged sharpshooter and Pierce's disease information, log on to American Vineyard's website, malcolmmedia.com, and follow the "GWSS" links. Daily, county-by-county updates are available from around the state.
Glassy-Winged Sharpshooter Update - 11/00
Vigilance Continues as More Finds Are Made
It's autumn. The days are getting shorter and the temperatures are dropping, but Pierce's disease (PD) and its most efficient vector, the glassy-winged sharpshooter (GWSS), continue to make the news in California agriculture.
The fight against GWSS has ebbed and flowed over the past weeks as summer waned and the grape harvest was in full swing. Those who were certain the sky was falling seemed to have been overestimating the pest's short-range effectiveness, while those who were certain there was no actual threat may have learned otherwise, and to their chagrin. It's probably accurate to say that the quick and decisive reactions to GWSS finds-including delimitation zones, spraying, and strict nursery stock inspections-slowed what might have been a blossoming catastrophe. Battles are being won.
It's also fair to say the war isn't over. Identification of PD infections and GWSS finds continue to be made even into the fall months, heralding a spring that should prove to be lively with anti-pest action.
In American Vineyard's continuing efforts to keep readers abreast of events in the grape industry, we offer the latest news in the Pierce's disease and glassy-winged sharpshooter imbroglio.
In late September, a single adult GWSS female was trapped in a Santa Ynez, Calif. (Santa Barbara County) neighborhood. This area of the county hadn't been infested prior to this trapping by the Santa Barbara County Agricultural Commissioner's staff. The find site was located approximately one-half mile from the nearest vineyard, which had already been harvested. No additional insects were found in subsequent searches, but traps continue to be set and monitored.
Another recent discovery occurred in the Central Valley, this time in the pest-active southeast Kern County, off of General Beale Road. A total of six grape vines were tested and found to be positive for PD, and were subsequently removed. The grower sprayed vigorously for adult GWSS, as the Kern County Ag Commissioner staff sampled the surrounding vineyards for further infestations and all life stages. It has been reported that in Kern County alone more than 300 grape vines are suspected as bearing PD, with lab results pending. Kern County has approximately 92,000 bearing and non-bearing acres of grapes, ranking it as the third largest producer of grapes in the state. Fresno, by way of comparison, leads grape-producing counties in California with about 235,000 acres.
Area growers and agriculture personnel are worried about this latest find and removal because of the echoes of Temecula, where, in 1997, the removal of a few vines due to PD infection led to thousands of uprooted vines just months later, and a decimated industry losing millions of dollars.
It was also announced recently that California Department of Transportation (Caltrans) workers would be trained to spot GWSS in its various forms along California's miles of oleander-lined roadways. The oleander is a known favorite of GWSS, and can be used as a jumping-off point into adjacent vineyards and orchards. Any finds along these highways will help the state map the progress of the pest.
"Critical scientific research is already underway that is helping the state develop long-term solutions to this threat," said CDFA Secretary William J. Lyons, Jr. "Meanwhile, the help of Caltrans staff is needed in the field to track the sharpshooter's movements so that we will know exactly where to focus our efforts."
Highways like Interstate 5 and Highway 99 point the way northward, where a GWSS find in Oregon means the pest has reached beyond California's borders, and into the 10,000-acre, $23 million Oregon wine grape industry. The Oregon Department of Agriculture imposed an immediate quarantine.
Nursery inspections turned up single adult sharpshooters in Stanislaus, Sacramento and Sonoma counties in mid-September. In Stanislaus County, the sharpshooter was found "adjacent to where the nursery unloads stock," according to Stanislaus County Assistant Ag Commissioner Dennis Dudgel. "We suspect it's a hitchhiker and arrived on a shipment of plants," Dudgel concluded. This followed a late-July discovery of a sharpshooter in a Modesto nursery, also in Stanislaus County.
Nursery owners have taken a real financial hit during this pest frenzy. As of August more than 80 separate GWSS egg, nymph or adult finds had been made in nurseries in 15 non-infested counties of Central and Northern California. In Kern County, one wholesaler has resorted to barricading his plants with netting to prevent GWSS infestation, and a Southern California nursery has stopped shipping plants from infected areas altogether, which amounts to a $5 million loss. Spraying and vigorous inspection also costs hundreds of thousands of dollars, and is being paid for by the nurseries themselves.
In late August and early September, parasitic wasps began to be released in Riverside, Kern and Ventura counties, but were denied to Fresno and Tulare counties in favor of continued spraying. The more than $40 million in damage done to Temecula-area vineyards was reason enough to schedule the release in Riverside County. But just two weeks after the Southern California release, officials decided to put off similar releases in the Central Valley because significant extant GWSS populations couldn't be found to ensure wasp survival. Spraying reduced populations around Porterville "significantly," according to officials, and they hoped that the spray regimen had kept the pest from expanding beyond delimited areas.
These same wasps have proven effective in Texas and Mexico against sharpshooters, laying eggs inside GWSS egg masses. Fresno County expects to receive shipments of the wasp from the state by spring 2001, says Jerry Prieto, Fresno County Ag Commissioner, and may begin releasing in the Fresno Street-Shaw Avenue area.
On the pesticide front, researchers have yet to find a one-size-fits-all solution for killing/controlling GWSS eggs, nymphs and adults. UC Riverside researcher Rick Redak has looked at many products to evaluate their effectiveness against sharpshooter egg masses, and has found five which seem to offer 100 percent nymph control. They are: Acetamiprid 70 wp, Marathon II, Merit 75 wp, Mesurol 50 wp, and Tame 2.4 ec. In trials the chemicals killed the nymphs as they emerged from the egg masses, though the embryos were unaffected. Redak recommends these for use in nursery treatments, and his findings are being evaluated by the California Department of Food and Agriculture (CDFA).
Surround (a kaolinic, white-clay material) is also being studied, and has been shown to be effective against adult psylla and their eggs on tree fruit, as well as other pests. Tests are underway in the Temecula Valley for Surround's effectiveness on grape vines and GWSS.
Funding continues to be a concern, as well. In late September the governor signed a $5.5 million spending bill to help the state's county ag commissioners combat exotic pests. Assembly Bill 1771, authored by Dean Florez (D-Shafter), also provides a perpetual status to the pest-fighting funds, something that didn't exist before. This means funds should be available (without legislative reauthorization) every year, if needed, to fight exotic pests that might threaten California's almost $27 billion agriculture industry.
The Pierce's Disease Advisory Task Force continues to meet and even grow. The panel discusses strategies to fight PD and GWSS, including the creation of protocols for nursery treatments and urban infestation control alternatives. The panel includes representatives from across the agricultural spectrum. Members hail from the grape, citrus and almond industries; they are winemakers, researchers, university personnel and ag commissioners; and the newest members include representatives from the Farm Bureau, the nursery industry and organic grape growers.
Steve Vasquez, UC Cooperative Extension, Fresno County, identifies the PD symptoms growers should have seen in the Fall if the bacteria causing PD (Xylella fastidiosa) were present in their vines:
· Older leaves display non-uniform chlorosis (yellowing) followed by necrosis (death). The symptoms normally begin on the margins of the leaves and will encompass the entire leaf over time. Leaf blades fall off at the petiole-leaf blade junction, leaving the petiole attached to the cane.
· Fruit shrivels on infected canes
· Canes display non-uniform wood maturity.
· Shoot tips burn back later in the season unless initial infection takes place near the shoot tip.
Vasquez also outlines the symptoms of PD-infection in the spring growth period:
· Delayed and stunted growth.
· Erratic bud break.
· Leaves tend to be small, chlorotic and distorted.
· Canes display dried xylem tissue when cut open.
Vasquez recommends that any grower suspecting PD infection should consult the Grape Pest Management publication available at Cooperative Extension offices, and have suspected tissue tested for the bacterium. Early testing can lead to more accurate vineyard mapping of the disease's progress, Vasquez concludes, and allows for a more controlled and efficient treatment and control regimen.
Finally, the inevitable heel-digging that appears during any crisis time can be witnessed in Northern California, where the "Northern California River Watch" is threatening lawsuits against any entity or person participating in aerial spraying to combat GWSS. This action would not include the use of ground applications, litigants say. The potential litigants are using the platform of the Clean Water Act in this proposed action, seeking to keep waterways unpolluted and all affected people in on the decision-making process.
For the latest glassy-winged sharpshooter and Pierce's disease information, log on to American Vineyard's website, malcolmmedia.com, and follow the "GWSS" links. Regular updates are available from around the state.
Glassy-Winged Sharpshooter Update - 12/00
Like a bad penny, it just keeps turning up.
The glassy-winged sharpshooter, that is.
On the heels of decisions to not release predatory wasps in the Central valley until at least next year, and the recent reactions to widespread spraying in Northern California, there's news of more sharpshooter finds, and in more far-flung areas.
An "infestation" has been officially declared in Chico, Butte County, coming in as the northernmost reaches-thus far-of the GWSS spread. Nine sharpshooters were found in or near a community park in Chico, and California Conservation Corps (CCC) personnel were called in and fanned out to try and determine the size and scope of the infestation zone.
The find occurred in mid-October. The first find in Chico was a single female in a trap set in a crepe myrtle tree, a trap placed by the county's agricultural commissioner's office. A subsequent delimitation search turned up eight more sharpshooters, according to Jay Van Rein, CDFA spokesman, necessitating the infestation announcement.
All the finds were near Highway 99. Caltrans workers were called in to assist in the delimitation process, searching the roadway easement for egg masses, nymphs and adults.
Another recent find occurred just days earlier in a Contra Costa County residential area.
A homeowner in a newer Brentwood residential area is credited with finding sharpshooters in his yard in this delta growing region. The homeowner had seen a photo of the sharpshooter at a local nursery, then went home and identified the culprit in his yard. County employees found multiple life stages of the sharpshooter on this property, and an infestation was immediately announced.
To date, more than 25 properties have been found to be infested though, as yet, no agricultural properties are threatened in Contra Costa County. The search continues, however. The infestation in Brentwood covered about 1/16th of a mile.
Single finds have been made at various Contra Costa County nurseries, though no infestations were declared. Every acre of grapes in the county (only 2,000) were searched earlier in the season, and the agriculture area declared pest-free.
According to Contra Costa County Agricultural Commissioner Ed Meyer, "At this point the infestation appears to be isolated."
"It's more territory to be concerned about the spread of the insect, but the good news is that it's fall," Van Rein said of the recent activity and interdiction, "and there's a good chance we can knock down the population and keep it contained over the winter."
A large cherry orchard sits across the street from the recent Contra Costa County finds. Cherry trees are host to GWSS, and surveys are underway. Intermittent rain and cooler weather have made the going more difficult, and finds less frequent. Both CDFA and CCC had crews onsite.
These most recent finds follow similar discoveries in other counties, including Santa Barbara, Kern (where Pierce's disease also was found, and vines removed), and Stanislaus, Sacramento and Sonoma counties.
Van Rein notes that the sharpshooter influence isn't just restricted to grapes or even crops in general. The little pests can have a negative impact on our daily activity.
"The grapevines are our big economic worry, but there's a lot more at risk here, Van Rein said. "This thing spreads disease to all kinds of plants. And now, in Southern California they're experiencing something called 'sharpshooter rain,' and it's not pleasant."
Van Rein explained that the fluid secreted by sharpshooters as they feed voraciously can become rain-like beneath heavily infested trees, making outdoor activities less-than-tantalizing.
"And that fluid has to go somewhere. It passes right through them, and if you're trying to have a barbecue under a tree with 100 of these things in it, you're going to understand the concept of sharpshooter rain," he said.
The Garin Ranch subdivision where the insect was found was scheduled for spraying just one week after the first insect find was made.
To date more than $36 million dollars has been allocated by the State to fight the infestations.
Glassy-Winged Sharpshooter Update - 3/01
Growers to Ante Up in GWSS Fight
The State Legislature is working on the financing side of this year's fight against the glassy-winged sharpshooter (GWSS), and it's the grower who's expected to feed the kitty.
Grape grower assessments are being written into new legislation by Assembly Member Patricia Wiggins, D-Santa Rosa. The grower participation will take the form of a $3 assessment per $1,000 of the grapes' worth when they leave the vineyard. This assessment would be applicable to crushed grapes, as well.
The assessment is targeting a $25 million goal over the next five years, with the raised funds going to research on Pierce's disease (PD), Xylella fastidiosa and GWSS. Work in progress includes the introduction of parasitic wasps to control GWSS populations, and a search is underway for a PD-resistant rootstock. There is currently no absolute cure for Pierce's disease. Infected vines are pulled out completely to curb the spread of the disease.
At the recent Unified Wine and Grape Symposium, myriad voices supported the proposal.
"The challenge is hard to overstate," said William Lyons Jr., State Secretary of Food and Agriculture. "This is the most significant threat to California agriculture in 20 years."
"If we are going to beat this thing, we need money," echoed Dana Merrill, CAWG chairman. "If ever there was a challenge that called for an assessment, this is it. Wine grapes need to lead the way."
This $25 million would be in addition to the $40 million already appropriated by the state to fight the disease. Many industry groups support the grower-funded measure, including its co-sponsors, the California Association of Winegrape Growers (CAWG) and Wine Institute.
"The growers feel strongly that the state and federal government have stepped up to control the movement of the pest," said Karen Ross, president of CAWG. "We have to find the cure."
The money is to be collected and paid to the state Department of Food and Agriculture, according to Ross, and will be disbursed by an advisory board.
The tax is scheduled to be repealed automatically on Jan. 1, 2006, unless the assessment is extended.
Glassy-Winged Sharpshooter Update - 4/01
California Legislature, Private Industry Attack Sharpshooter
Government and private industry are working at both ends to solve the glassy-winged sharpshooter (GWSS) problem.
California State Assemblymember Patricia Wiggins (D-Santa Rosa) has introduced legislation which aims to raise $25 million to fund research on the GWSS, the most potent vector of Pierce's disease (PD). The bill, AB 1394, proposes to raise $5 million yearly for the next five years from assessments on all grapes grown for processing. Assembly co-authors are members Canciamilla, Cardoza, Florez, Frommer, Maldonado, Nation, Pescetti, Strom-Martin and Thomson. Senate co-authors are Alpert, Chesbro and Costa.
Tomen Agro, a supplier of crop protection products, has pledged a substantial donation to the American Vineyard Foundation to support its GWSS/PD research support program. The donation will be derived from sales of its Elevate Fungicide to the California grape market during the 2001 growing season.
The Wiggins legislation has resulted from the collaboration of several segments of the wine industry, including the California Association of Winegrape Growers (CAWG), Wine Institute and Family Winemakers of California. Wiggins' Chief of Staff, Matt Riley, hopes that the legislation will have passed the Assembly agriculture committee and any other policy committees soon, allowing it to reach a floor vote by the end of April. "It's mostly the committee process that takes a while," said Riley when interviewed in March. "When it goes to the Senate, the bill will need to pass their ag, water and appropriations committees before it goes to the Senate floor and if they make any amendments, it goes back to the Assembly for concurrence. It could be through by June, but realistically it may be this July."
The terms of AB1394 call for an assessment on all California grapes crushed for wine, wine vinegar, juice, concentrate and beverage brandy. Producers would be charged a maximum of $3 per $1,000 value of their grapes final purchase price. For grapes that are not purchased (processor or custom crushed), the assessment is to be made on the weighted average producer return by type, variety and district, as reported in Table 10 of the Annual Grape Crush Report. The bill includes a "sunset" provision so that if it is not specifically renewed, it will expire as of January 1, 2006. There is an urgency clause to allow the law to become effective upon the Governor's signature.
Dana Merrill, chairman of CAWG, commented, "While the state and federal government have already spent millions on programs to control the spread of the Glass-winged Sharpshooter, we in the wine industry feel that voluntary funding of research efforts is no longer enough. By working together and sharing the cost, we hope to accelerate the scientific search for a solution to this serious threat sooner." Bob Steinhauer agreed. The chairman of the Wine Institute Committee on GWSS/PD and Senior Vice President of Vineyard Operations for Beringer Vineyards, called the effort, "an outstanding example of growers and vintners working together to achieve a common goal. The Wine Institute and CAWG have worked extremely hard to develop an industry-wide consensus."
On February 28th California Food and Agriculture (CDFA) Secretary Bill Lyons led a group of Californians to Washington, D.C. to explain the value and importance of the program. Accompanied by Bob Wynn, Statewide Coordinator of the Pierce's Disease Control Program, and representatives from the citrus, nursery and winegrape industries, he met with officials of the U.S. Department of Agriculture and California Congressional representatives.
A member of the group which visited Washington was Karen Ross, President of CAWG, who said that the plan got a lot of notice, "We know that the ag economy generally has been hurting and sponsoring an assessment bill (at this time) is not a popular thing to do. Under normal circumstances we would not casually introduce legislation to assess ourselves. But we don't get to pick when disaster or crisis faces us and we (had to act). I think this is the best response to fund science to find a cure for Pierce's disease. It is the role of government to protect the state's borders and none of us wants to set a precedent by this action, but it certainly demonstrates to state and federal government how serious this issue is because of our willingness to do this."
The Wiggins bill would create the Pierce's Disease and Glassy-winged Sharpshooter Board, a group of at least 14 and no more than 15 members. These would include seven from the grape growing segment and seven from processing section of the industry. A 15th member-at-large could be appointed by California's Secretary of Food and Agriculture. This group would be responsible for setting the annual assessment rate of no more than $3 per $1000 in value of processed grapes. Processors are to be notified of the assessment rate by July 15th of each year. The assessment is to be deducted from the producers' proceeds and remitted to the Department of Food and Agriculture by January 10th. The only remedy for nonpayment of the assessment fee is civil action to collect, a penalty of 10 percent of the amount due, and interest at the rate of 1.5 percent per month on the unpaid balance. The Board is also to be charged with the allocation of the funds for research of integrated pest management and other sustainable practices related to the transmittal of the Pierce's disease bacterium.
Tomen Agro is basing its donation to the American Vineyard Foundation (AVF) on 2001 sales of its flagship product, Elevate Fungicide, in the California grape market. Mark Quick manages sales for the fungicide for all U.S. markets. "Since everyone involved in California agriculture has a vested interest in finding a solution to this problem, Tomen Agro wanted to show our support in a very tangible way," he said. "By donating a portion of the proceeds of Elevate sales in the California grape market, we are supporting the growers who support us. In the final analysis, we expect our donation to total tens of thousands of dollars."
"This is such a potentially devastating problem. We wanted to show our support of the industry, to say thank you," Quick said. "A contribution will be made based on a percentage of all sales of Elevate to California's grape industry. We expect the donation to amount to tens of thousands of dollars."
"The AVF is very appreciative of the GWSS/PD research contribution from Tomen Agro," commented Patrick Gleeson, Executive Director of the American Vineyard Foundation. "As we have stated from the outset of this issue, GWSS/PD is an agricultural issue that impacts many related business, not just wine grapes. In supporting GWSS/PD research programs, Tomen Agro is taking an active role in finding a solution to this problem."
Glassy-Winged Sharpshooter Update - 7/01
Plant Inspection Program Off to Strong Start in Sonoma County
Seventy Sonoma County nurseries, retail establishments and landscape businesses are already participating in a plant inspection program designed to keep the disease-transmitting Glassy-Winged Sharpshooter out of Sonoma County, it was announced today by John Westoby, Sonoma County Agricultural Commissioner. The goal of the program is to prevent introduction and spread of Sharpshooter-transmitted disease to the County's agricultural and horticultural crops and to the gardens and yards of County residents.
The GWSS pest problem is best known for its devastating effects on vineyards, through its ability to transmit the potentially lethal bacterial scourge known as Pierce's Disease. However, the GWSS has a wide range of plant hosts including an array of citrus, plants such as oleanders, azaleas and roses, trees such as sycamore, eucalyptus and oak, and other crops such as alfalfa and almonds. The current list of plants that serve as a host to the insect can be found at http://pi.cdfa.ca.gov/pqm/manual/454.htm#gwhostlist.
The insect and the diseases it can spread threaten many key agricultural and horticultural crops throughout California. In addition to spreading diseases from plant to plant, an adult GWSS drains approximately 200 to 300 times its body weight in water out of plants it feeds on each day. This dehydration renders plants even more susceptible to death from wilt, insect blight and disease.
Many nurseries, landscapers and garden stores throughout Sonoma County are already participating in the program that includes inspection of incoming plants, reporting the presence of any signs of the insect or infestation, and disposition of any infested nursery stock. The Sonoma County Agricultural Commissioner's office, with funding from grape growers and wineries, supplies participants with training materials to help employees learn to recognize signs of Sharpshooter infestation and take appropriate action. Participants receive Certificates of Compliance to be displayed at their establishments and a "Sharpshooter Seal" that can be included in advertising to notify the public that they sell only inspected plants. Participating businesses also receive pamphlets to be given to customers to educate them about the GWSS. Additionally, participants names will be included in lists of compliant organizations given to the media and published online at www.bugspot.org to help residents identify local establishments that sell inspected plants.
"The Glassy-Winged Sharpshooter and the diseases it transmits threaten the economic and ecological base of Sonoma County, and hamper the ability of all residents and visitors to enjoy the beauty and enormous bounty of the region," commented Westoby. "We are thrilled that the owners and operators of nurseries, garden stores and landscape businesses have embraced this inspection program for the benefit of all residents and visitors to the County. Their efforts are invaluable in preventing the spread of the GWSS and the diseases it transmits, and we applaud them for their commitment of time and resources. We hope residents of Sonoma will really show support for these businesses."
"We are doing everything we can to keep the Glassy-Winged Sharpshooter out of Sonoma County," said Mick Prickett, owner of Prickett's Nursery in Santa Rosa, one of the first establishments to sign up for the inspection program. "The County, together with the grape growers and wineries, is providing us with tools for training our staff, educating our customers, and promoting the program. We're really pleased that the California Association of Nurserymen is working with the County, too. Best of all, customers really seem to appreciate our commitment to providing plants that are free of the GWSS. The program creates loyal customers and a lot of good will. We hope everyone in Sonoma County will work together with us and the new education program that's being put together. If we can all tell our friends and families about the importance of prevention and early detection, hopefully we can prevent an infestation here."
While the County and local nurseries, retailers and landscapers are inspecting incoming plant shipments, Sonoma County's new education program, funded by grape growers and wineries in Sonoma County, is focused on letting residents know what they can do to try to keep the insect out of the County, or detect it as early as possible, if it does make its way into the area. Residents who took the time to look around their own yards have been credited with many sightings of the insect throughout California.
The education program will provide materials to all participating nurseries, as well as other locations in Sonoma County, including banks, wineries, libraries, grocery stores, offices, gas stations, coffee shops and many other public locations. A science-based curriculum is available for students who are interested in learning more about insects in general, and how to spot GWSS. Speakers will be available to conduct short presentations to groups who are interested in learning about the insect and what they can to help prevent an infestation. Volunteers interested in helping are asked to call 707-591-0407.
The program will offer free posters, informational pamphlets, videos and other materials in English and Spanish. Information about organic and conventional options that may eradicate the insect will be available to the public, as well as information for those who are medically sensitive to use of pesticides. A website, www.bugspot.org, has been developed in conjunction with Napa County, and will be updated with new information as it becomes available. A toll-free phone number, 1-866-BUG-SPOT has been established so residents can let each County's Agricultural Commissioner know if they have found possible signs of a Glassy-Winged Sharpshooter.
Glassy-Winged Sharpshooter Update - 8/01
By Darl Larsen, Associate Editor
The fight against the glassy-winged sharpshooter (GWSS) is in its second year, and the indications are that this sophomore season looks promising. Thus far, both the number of sharpshooter finds (egg masses, nymphs and adults) and the number of spraying sites are down considerably compared to this time last year. As of late June and early July, treatments for GWSS continued in parts of Fresno County, specifically in the area of Fresno and Shaw in the north. Those treatments continued into the middle of July.
Also significant is the ongoing pilot project in Kern County, the site of the Valley's heaviest infestation last year. The Kern County Pilot Project is performing perhaps better than anyone expected, with concrete indications that control measures already implemented are working very well. Trapping data showed an average of just 1.6 sharpshooters per trap within the treatment area, as opposed to traps outside the control area, which averaged 56.8 GWSS/trap.
The Pilot Project is being conducted in the General Beale Road area, and covers about 13,000 acres of agricultural land home to significant levels of Pierce's disease (PD) last year, and loaded with GWSS, as well. "Different methodologies" are being employed against the pest within the treatment area, according to participating researchers.
Recent survey and treatment actions in the state include, from the California Department of Food and Agriculture's (CDFA) information:
· May 24-Single nymph trapped in Chico, Butte County.
· June 14-Two adults trapped in Chico. On June 21, five commercial properties, along with portions of the landscaping along the Highway 99 corridor, were treated.
· June 11-15-A visual survey was conducted in Brentwood, Contra Costa County, with no finds. This was the third such survey of the year.
· June 5-21-A survey was conducted in Clovis, Sunnyside, Woodward Park and the Fresno/Shaw areas in Fresno County. GWSS finds were made in each area. However, just 127 properties were treated during that period, compared to a staggering 1,000 and more last year. Treatments began on June 5, and continued through June 21. Treatments continued in the Fresno/Shaw area through the end of June.
· June 22-In Sacramento County, the Rancho Cordova area, a single adult was trapped within a previously treated area, and surveys intensified.
· May 24-June 12-In the Porterville and Terra Bella areas of Tulare County, finds were made in both areas, but with both also reporting fewer infestations than last year. In Porterville, 329 properties were treated as of the end of May, and in Terra Bella 28 properties were treated during the same period. On June 12 a single new infested property was discovered in Porterville. Treatments of that property and those in proximity began immediately.
· June 26-Six new infested properties were discovered in the Porterville area, and were treated on June 28.
· May 22-June 5-In Imperial County, in Salton Sea Beach and Desert Shores Imperial Spa, GWSS finds were made. Nymphs and egg masses were discovered. A delimitation survey followed.
· July 5-In south San Jose area, two adults trapped and delimitation and treatment followed.
The California Department of Food & Agriculture's (CDFA) Pierce's Disease Advisory Task Force met in June, as well. Appointed by CDFA Secretary William (Bill) J. Lyons, Jr., the task force is charged with overseeing the statewide efforts in combating GWSS and PD.
It was also announced recently that AB 1394-an assessment bill designed to raise funds for the GWSS and PD fight-has passed through the Legislature and emerged from the Senate Appropriations Committee. Proponents are certain that the governor's signature is a given, and that the intended $5 million will soon begin to be collected.
The bill's language includes the creation of the Pierce's Disease and Glassy-winged Sharpshooter Board to be made up of industry members, and set to allocate research funds. The assessments would be on California-grown grapes crushed for wine and juice products, at the rate of $3 per $1,000 of grapes.
In recent news from Washington, the House passed a bill that would "earmark" about $3 million to the ARS's research efforts in the Valley. The bill still must face Senate confirmation, where significant changes could be instituted by October 1. The bill is a part of a $76 billion agriculture package.
Glassy-Winged Sharpshooter Update - 9/01
Reduced Finds Compared to Last Year
Statewide activity in July and August included reduced finds as compared to last year at this time, and a resulting reduction in applications of pesticides for control purposes. According to the California Department of Food and Agriculture (CDFA), inspection and control activities continued throughout the following counties and cities:
· In Butte County, Chico, sharpshooter adults and nymphs were trapped on three occasions in July, and a survey was completed with the assistance of the California Conservation Corps (CCC). Foliar treatments in infested areas of Butte County began August 11. In Contra Costa County, Brentwood, monitoring continued in residential areas, and 2 finds were made on July 2 and 16 in a nursery.
· Fresno County activity was centered in the Clovis, Sunnyside, Woodward Park and Fresno/Shaw areas, where finds continue to be far below last year's rate. More than 8,311 properties have been surveyed countywide, with only 355 infested properties reported, with 232 treated. Surveys continue in Imperial and Sacramento counties, where single adult finds were made on July 10 and 18, respectively. In Imperial County, two adults were trapped July 30, and in Sacramento County, one adult was trapped on July 27 in a residential area.
· In Santa Clara County, specifically the San Jose area, imidacloprid treatments on crepe myrtle trees were performed (via soil injection) in mid- to late July, followed by foliar (Carbaryl) treatments. Scattered GWSS finds continue to occur as delimitation activities are carried out in the San Jose area, with treatment continuing into early August. Finally, in Tulare County, the Porterville and Terra Bella areas, the most recent reports are encouraging: Fewer finds than during last year's surveys. Activity in Tulare County has been greatly reduced since late May, with only three finds in all of June, and only 404 properties treated.
On the legislative front, the governor recently signed AB 1394, a bill which will assess the California wine grape industry to finance the battle against sharpshooters. The bill will raise $5 million to contribute toward, among other things, the search for a cure for Pierce's disease, according to Davis.
The assessment amounts to $3 per thousand dollars of grape farmgate value for the 2001-2002 season, and will apply to grapes "for wine, concentrate, juice, vinegar and beverage brandy," according to the bill. The bill does take effect immediately, as it is an emergency measure.
Also on the legislative side is the recent approval by the U.S. House of Representatives of the nearly $75 billion FY 2002 Agriculture Appropriations bill. The bill included $15 million earmarked for GWSS and Pierce's disease research, to be divided between the ARS facility at Parlier, California university research centers, and the Animal and Plant Health Inspection Service (APHIS). That's the good news. The downside is that a cantankerous Senate must also consider the bill. The better news must be that the Senate Appropriations Committee recently approved $12 million appropriation to fight PD, and the appropriation goes to the full Senate for consideration.
Also significant to the GWSS and PD fight is the opening of UC Riverside's Insectary and Quarantine facility, where exotic pest research can address both the abatement and even cure for this grape scourge. See the related story in an upcoming issue of American Vineyard.
In a related but sad note, Tulare County Deputy Ag Commissioner Charles "Lynn" Thomas was killed in July in a head-on collision with a suspected drunk driver. Thomas was in direct charge of the successful and effective Porterville GWSS abatement program, and had been in his current deputy ag post for 12 years.
In the ongoing Kern County study, treatments for GWSS populations in citrus are underway, with encouraging results. After Evergreen treatments, significant reductions of GWSS populations (up to 90 percent, first instar) have been recorded. GWSS activity and populations in area windbreaks are also being studied, with trappings being monitored to determine the effectiveness of windbreak pesticide treatments.
In a public outreach move recently, Sonoma County Agricultural Commissioner John Westoby responded to a letter to the editor in the Santa Rosa Press Democrat by first lauding nursery owners for their continuing vigilance, and then asking the general public to join the fight against GWSS by examining the plants in and around their homes. Westoby concluded that the state and county employees couldn't carry the entire burden, and that vigilance in landscape and fruiting plants and trees was essential for the ultimate control of the sharpshooter.
Glassy-Winged Sharpshooter Update - 10/01
The fight goes on
According to the California Department of Food and Agriculture (CDFA), inspection and control activities continued throughout August and September in the following areas:
· In Butte County, Chico, four adults were trapped on July 24, and on July 31 one nymph was trapped at a commercial property. Foliar treatments in infested areas of Butte County (eight properties) continued through late August and into early September. Systemic treatments were also expected in the infested areas. In Contra Costa County, Brentwood, monitoring continued through August and into September. No residential GWSS finds have been made in Contra Costa County (Brentwood) since October 2000.
· Fresno County activity continued to center in the Clovis, Sunnyside, Woodward Park and Fresno/Shaw areas. More than 8,311 properties have been surveyed countywide, with 379 infested properties reported, and 349 treated. County personnel indicate that GWSS finds in Fresno County continue to be lighter than last year.
· Surveys continue, as well, in the infested areas of Imperial and Sacramento counties. Action in Imperial County is centered in the Imperial Spa/Bombay Beach areas, where two adults were trapped in late July, and one adult in mid-August. In Sacramento County (Rancho Cordova), one adult was trapped in a mobile home park in mid-August, and pesticide applications were made in mid-September in a portion of that mobile home park.
· In San Luis Obispo County, Nipomo, "viable life stages" of GWSS were discovered in a nursery in mid-August. The nursery was immediately treated with Carbaryl, and a subsequent delimitation survey turned up no infestation. In Santa Barbara County, GWSS eggs were discovered in rosebushes in Los Alamos. The plants were immediately sent back to Riverside County.
· In Santa Clara County, specifically the south San Jose area, multiple finds were made in August and September, and delimitation activities also discovered new infested areas. Imidacloprid treatments (soil injection) followed, as did Carbaryl foliar treatments. Parasitoid wasps were also released in mid-August in three different sites in south San Jose. In Tulare County, Porterville, the most recent GWSS trappings occurred in June. Just 470 properties have been treated this year in the area, which was ground zero for GWSS last year.
· In Sonoma County, an accord was reached between farmers and environmental groups regarding treatment methods for GWSS infestations. Organic treatments are to be the first line of attack, followed by synthetic pesticides, if necessary. The new plan is supported by both Sonoma County and CDFA, and is a preemptive move, since GWSS has yet to be detected in the county.
In Kern County, along with a pilot program researching GWSS in buffer areas and host crops, education is also underway for farm workers to help them prevent the movement of sharpshooters on farm equipment and in loads of newly harvested grapes.
Glassy-Winged Sharpshooter Update - 11/01
Infestations Down, Risks Still High
American Vineyard continues to compile and provide the latest information from the glassy-winged sharpshooter front, even now as the 2001 crop season winds down. Following is a rundown of recent anti-GWSS activity in California.
· In Butte County, Chico, one nymph and nine adults were found on October 5. Survey and treatment of the infested area followed beginning October 15. In Contra Costa County, Brentwood, monitoring continued through September and into October.
· Fresno County activity continued in the Clovis, Sunnyside, Woodward Park and Fresno/Shaw areas. More than 12,488 properties have been surveyed countywide, with 385 infested properties reported, and approximately 375 treated (with Merit). GWSS infestations in Fresno County continue to be much lighter than last year. Parasitoids were also recently released in the Sunnyside and Woodward areas, and are scheduled for future releases.
· Surveys continue, as well, in and around the infested areas of Imperial and Sacramento counties. One adult was trapped in mid-August in the Imperial Spa/Bombay Beach areas. In Sacramento County (Rancho Cordova), one adult was trapped in a mobile home park in mid-August, and pesticide applications were made September 18-21 in a portion of that mobile home park. On September 14, four additional adults were found.
· In Santa Clara County, specifically the south San Jose area, multiple finds were made in August and September, and delimitation activities also discovered new infested areas. Imidacloprid treatments followed, as did Carbaryl foliar treatments. Parasitoid wasps were also released in mid-August in three different sites in south San Jose.
· In Tulare County, Porterville, the most recent survey of 15,351 properties found 796 infested, treatment began in the infested areas on October 9, and nearly 300 hundred sites had been treated by press time.
· Kern County has reported a decrease in GWSS finds, and officials attribute the reduction to both cooler temperatures and the effectiveness of treatment programs.
Also in Kern County, the Bakersfield Californian has reported that even though this year's occurrences of sharpshooter infestations are well below last year's levels, the effects of GWSS infestations and the accompanying Pierce's disease symptoms can still be devastating. The increasing infestation of a particular 20-acre vineyard in Kern County with Pierce's disease points up the continuing effects of even a reduced GWSS infestation.
A recent seminar conducted by the UC Cooperative Extension (and grape advisor Jennifer Hashim) outlined the effectiveness, thankfully, of in-place and on-going strategies meant to reduce and even eliminate the spread of the grape disease in the county and beyond.
The trapping of GWSS in previously infested areas of Kern County has dropped dramatically, according to UC personnel, a sign that control and contain methods are working. According to CDFA sources, the intense surveys and studies being performed in portions of Kern County should be expanded throughout the Central Valley-and eventually the entire state-effectively getting the jump on GWSS and Pierce's disease. Grape growers are footing about one-fifth of the bill for the broadening project.
In late September in Fresno County, 1,400 parasitic wasps were released along Shepherd Avenue in north Fresno. These Mexican predators (Gonatocerus triguttatus) were bred in California just for this purpose, and will attack sharpshooter egg masses, laying their own eggs in the sharpshooter eggs. This release signaled the first such wasp release in the Central Valley.
Two additional releases followed the late September event, both along the same stretch of heavily-infested trees and bushes in Fresno County.
In San Joaquin County, agricultural officials announced that they are increasing their vigilance, and are inspecting as many as 3,000 residences and yards for any sign of GWSS infestation. By mid-September, more than 1,500 residences had been checked, and officials say they are focusing on newer subdivisions that are more likely to have larger numbers of newly-planted nursery plants. The sharpshooters are known to travel in shipments from Southern California nurseries. More established neighborhoods in the county that happen to be in the area of nurseries are also targeted for close inspection. More than 4,200 traps have been set since May in San Joaquin County.
In sharpshooter-related news, it was also reported recently that many vineyard owners in the Temecula region have begun the optimistic process of replanting their vineyards. Temecula has, of course, suffered greatly due to Pierce's disease-caused vine loss, and cost the area millions of dollars in damage. And because Chardonnay has been so effected by Pierce's disease, vineyard owners are planting just about any other variety. New plantings are being treated with Admire to give them a better-than-fighting-chance of survival.