Scientists Sharpen Strategies To Sabotage Glassy-Winged Sharpshooter

PATRICK TREGENZA (K5633-46)

half-inch-long called the coast to coast—and in South glassy-winged sharpshooter has America—are making the wreaked havoc in southern Califor- sharpshooter and the Xylella Ania wine vineyards, causing an esti- microbe the focus of ambi- mated $14 million in damage during the past tious new studies. The re- several years. The sharpshooter carries the searchers are investigating Xylella fastidiosa bacterium, the cause of the promising particle films, in- Grape vines are a incurable Pierce’s disease of grapevines. Known secticides, and biological con- favorite target of the to scientists as Homalodisca coagulata, the trol agents that might sabo- glassy-winged sharpshooter. lively leafhopper is now set to attack other grape- tage the sharpshooter. They’re growing regions in the Golden State as well. delving into the basic biology of both the insect To rout this pest, scientists at ARS labs from and the bacterium. And they’re pursuing new

PEGGY GREB (K9664-1)

Glassy-winged sharpshooter on a grape leaf. ways to quickly and easily detect the mi- are part of the study, which is coordinat- early-season use. But after the vines crobe in sharpshooters and in afflicted ed by USDA’s and Plant Health bloom, he notes, table grape growers plants. Inspection Service (APHIS). would have to switch to insecticides. Here’s a look at some of those “Participating growers use products “The Surround treatment, if continued, investigations. that have minimal toxicity, whenever would leave a white residue on the possible, in order to spare beneficial stems,” Luvisi explains. “The residue is A Particle Spray Keeps Sharpshoot- harmless, but it probably would be ers Away PEGGY GREB (K9660-3) unacceptable to consumers.” A coating of white kaolin particles, co-developed by ARS entomologist Insecticides Investigated Gary J. Puterka, can make grapevines in- To learn more about insecticides that hospitable to sharpshooters. can safely and effectively zap the sharp- “The specially shaped and sized par- shooter, ARS researchers David H. Akey ticles stick to the sharpshooters’ legs and and Thomas J. Henneberry of the wings when they land on treated foliage, Western Cotton Research Laboratory in making it a very uninviting place for din- Phoenix, Arizona, have teamed up with ing on or laying eggs,” explains Puter- entomology professor Nick C. Toscano ka. He is with the ARS Appalachian Fruit of the University of California at Research Station in Kearneysville, West Riverside to scrutinize some of the most Virginia. promising compounds. The product, sold by Engelhard Cor- In one series of experiments, they took poration under the trade name Surround sharpshooters that were living on citrus WP Crop Protectant, has been very suc- trees and moved them to a southern Cal- cessful in protecting pears and apples ifornia vineyard of Chardonnay grapes. from insect pests. On one vine in each plot, the scientists “Given a choice between treated and enclosed 25 sharpshooters in an impro- untreated foliage, glassy-winged sharp- vised cage made of soft netting. They shooters are highly unlikely to settle on then sprayed an insecticide in two appli- Surround-treated foliage,” says Puterka, At the University of California at Riverside, cations, spaced 1 week apart. They re- who tested it this year on table grapes ARS technician Doug Diaz (left) and field peated this procedure in their tests of growing in central California’s Kern worker Vince Lyons count glassy-winged about two dozen different insecticides. sharpshooters on a grapevine treated with County. The vineyards he used border Surround WP. The researchers inventoried the cag- citrus groves, which can harbor the es for dead sharpshooters at 6 hours and sharpshooter. at 1, 2, and 6 days after spraying. Then, Puterka and collaborators wanted to for the next 15 to 29 days, they periodi- see if Surround would prevent the six- ,” says APHIS entomologist cally restocked the cages with new sharp- legged varmints from moving into the Matthew A. Ciomperlik. “Surround, shooters to determine whether the aging vineyards after wintering in citrus. Af- which is completely nontoxic, clearly residue of the chemicals had any effect ter three treatments from mid-March outperformed insecticides and is proving on the insects. through mid-April 2001, the scientists to be very economical and effective at “We were particularly concerned with found that the number of sharpshooter preventing the insect’s spread. Growers how fast the insecticides knocked down trap catches and eggs was far lower in needed to use only three applications of the sharpshooter,” says Henneberry. the Surround-treated areas than in the Surround versus six of insecticides. So “That’s especially important if an pesticide-treated areas. Surround might help them cut costs. insecticide is used for stopgap protection Puterka got similar results from a Some growers who were reluctant to try when a new infestation is discovered. Not larger pilot study in Kern County. It is Surround changed their minds when they all scientists agree about exactly how fast the first project aimed at developing an saw how effective it was.” a feeding sharpshooter can transmit the economically feasible, areawide strate- Donald A. Luvisi, a Kern County farm bacterium into a grapevine. But, in the gy to quell the pest. Specialists from Cal- advisor with the University of Califor- ideal scenario, the insecticide would kill ifornia state and county agencies, along nia’s Cooperative Extension Service, the sharpshooter before the bacterium with 30 growers and numerous advisors, sees Surround as very promising for could enter the plant.”

21 REYES GARCIA III (K9667-1) In general, compounds known as already been released in Califor- pyrethroids and neonicotinoids were the nia by researchers at the Univer- best performers, according to the re- sity of California at Riverside and searchers. One pyrethroid killed all the APHIS. Now, ARS-sponsored caged sharpshooters within 6 hours. studies may uncover other prom- Based in part on the team’s studies, the ising parasitoids. pyrethroid cyfluthrin is already approved At the ARS South American for sharpshooter control. Pyrethroid and Biological Control Laboratory in neonicotinoid residues were still killing Hurlingham, Argentina, research- sharpshooters after 28 days. ers are investigating the para- sitoids that emerge from the eggs Seeking Egg Parasitoids of a native South American This parasitic wasp, triguttatus, lays its One of the trickiest aspects of using sharpshooter, Tapajosa rubri- eggs in glassy-winged sharpshooter eggs embedded these or other insecticides is making sure marginata. in a leaf. that the chemicals don’t clobber bene- “In field experiments so far, ficial insects, such as natural enemies of we’ve found that parasitoids the sharpshooter. Among the sharp- emerged from 66 to 71 percent of the Jones, “We think this parasitoid is at least shooter’s most formidable foes, for eggs. That’s a fairly impressive rate of partly responsible for the lack of glassy- example, are egg parasitoids—insects parasitization for an experimental situa- winged sharpshooters in that region.” that unabashedly lay their eggs inside tion,” says Guillermo Logarzo. He is —By Marcia Wood and Judy McBride, sharpshooter eggs. Parasitoid young based at the Hurlingham laboratory. ARS. hatch inside the sharpshooter eggs, then Serguei V. Triapitsyn, a wasp expert This research is part of Crop Protec- proceed to feast on them. from the University of California at Riv- tion and Quarantine, an ARS National One egg parasitoid, a tiny, stingless erside, is collaborating with the Hurling- Program (#304) described on the World wasp called Gonatocerus triguttatus, has ham scientists. Some of the Argentine Wide Web at http://www.nps.ars.usda. species of wasps that he has identified gov. so far are very different from parasitoids Gary J. Puterka is with the USDA- PEGGY GREB (K9662-1) that beleaguer the sharpshooter in North ARS Appalachian Fruit Research Sta- America. tion, 45 Wiltshire Rd., Kearneysville, WV The ARS Beneficial Insects Research 25430; phone (304) 725-3451, ext. 361, Unit in Weslaco, Texas, is helping fund fax (304) 728-2340, e-mail gputerka@ the Hurlingham studies. Says Walker A. afrs.ars.usda.gov. Jones, who leads the Weslaco research David H. Akey and Thomas J. Hen- unit, “Parasitoids or other sharpshooter neberry are with the USDA-ARS West- natural enemies from subclimates simi- ern Cotton Research Laboratory, 4135 lar to the grape-growing regions of E. Broadway Rd., Phoenix, AZ 85040; California might outperform natural phone (602) 437-0121, fax (602) 437- enemies imported from other climates. 1274, e-mail [email protected], Our survey of areas where sharpshooter [email protected]. species occur showed that subclimates Guillermo Logarzo is with the USDA- in some areas of Argentina match those ARS South American Biological Control of California. In addition, Chile has some Laboratory, Bolivar 1559, 1686 Hurling- exact matches, so it’s being included in ham, Argentina, phone/fax 53-11-4662- explorations for new biological control 0999, e-mail [email protected]. agents.” Walker A. Jones is in the USDA-ARS But researchers aren’t ruling out Beneficial Insects Research Unit, Kika potential biological control agents from de la Garza Subtropical Agricultural Re- other regions. For instance, the Weslaco Matthew Blua, entomologist at University search Center, 2413 E. Highway 83, of California at Riverside, beats an orange scientists and their colleagues are hot on Weslaco, TX 78596; phone (956) 969- tree to shake loose glassy-winged the trail of an egg parasite found in south 4852, fax (956) 969-4888, e-mail sharpshooters. Texas and in northeastern Mexico. Notes [email protected]. ◆