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Scientists Sleuth Glassy-Winged Sharpshooters' Hangouts

By Marcia Wood
February 18, 2004

No one can say for certain where the glassy-winged sharpshooter, a half-inch-long pest of grapes and other crops, prefers to live. To find out, Agricultural Research Service scientists are investigating where sharpshooters are most likely--at any given time of the year--to rest, feed, lay their eggs or, perhaps most important, to ingest and transmit Xylella fastidiosa, a bacterium harmful to plants.

This microbe causes Pierce's disease of grapes. What's more, in other plants, X. fastidiosa causes other diseases, such as almond leaf scorch and citrus variegated chlorosis. Glassy-winged sharpshooters that feed on infected plants can spread the bacteria.

In the past decade, Pierce's disease has caused approximately $14 billion in crop losses and pest control costs in southern California vineyards. But losses could reach even higher levels if this insect, first detected in California in 1989, continues to expand its range.

To learn more about glassy-winged sharpshooters and other insects that transmit X. fastidiosa, ARS entomologist Russell L. Groves is meticulously monitoring an extensive network of insect traps that he has established in glassy-winged sharpshooter infested areas of California's central San Joaquin Valley. He's based at the ARS San Joaquin Valley Agricultural Sciences Center in Parlier.

The traps, hung from poles, are made of panels of bright-yellow cardboard coated with a sticky substance. Glassy-winged sharpshooters, attracted to the bright color, end up stuck to the panels.

Once a week, year-round, Groves checks these traps to determine changes in the abundance of the insect from season to season and to delineate variations in the glassy-winged sharpshooters' use of plants in and around vineyards, orchards and fields.

Results from this research should help growers get more from their pest-control dollars. For example, the investigation may yield new, more precise information about where insects acquire X. fastidiosa in the central San Joaquin Valley, at what point they move into vineyards, and when they spread the bacterium into grapes.

ARS is the U.S. Department of Agriculture's chief scientific research agency.