Sharpshooters becoming targets is unusual, but through an ambitious new research program that is what's happening to the glassy-wing sharpshooter, an insect pest costing California vineyards more than $14 million annually. The sharpshooter carries the bacterium Xylella fastidiosa, which causes incurable Pierce's disease of grapevines.

Taking a team approach to finding insecticides that can safely and effectively zap the sharpshooter, Agricultural Research Service scientists David H. Akey and Thomas J. Henneberry of the Western Cotton Research Laboratory in Phoenix, Ariz., allied with entomology professor Nick C. Toscano of the University of California, Riverside. They scrutinized the most promising compounds, with pyrethroids and neonicotinoids being the best performers.

In Argentina, scientists at the ARS South American Biological Control Laboratory at Hurlingham are investigating beneficial wasps that are powerful natural enemies of the sharpshooter. These wasps are egg parasitoids, meaning they lay their eggs inside the sharpshooter eggs. The wasp young then feast on the sharpshooter young.

ARS helps fund study

Helping to fund the Hurlingham studies is the ARS Beneficial Insects Research Unit in Weslaco, Texas. In addition, Weslaco researchers are seeking potential biological combat agents from other regions, particularly another egg parasitoid found in south Texas and northeastern Mexico. This parasitoid may be partially responsible for the lack of glassy-winged sharpshooters in those regions, according to Walker A. Jones, leader of the Weslaco unit.

White clay coating

Another technique for fending off the sharpshooters is coating the grapevines with white clay, which makes the vines inhospitable to the pests. ARS entomologist Gary J. Puterka co-developed the white clay coating, now sold by Engelhard Corp. under the trade name, “Surround.” Puterka works at the ARS Appalachian Fruit Research Station in Kearneysville, W.Va. At test vineyards in Kern County, Calif., Puterka and colleagues found the white clay coating outperformed insecticides, as growers needed only three clay coatings in contrast to six insecticide sprayings.