The word “wired” has taken on new meaning in California research about a grapevine enemy called the glassy-winged sharpshooter. Agricultural Research Service research entomologist Elaine A. Backus is attaching thin, gold wires to the backs of these half-inch-long insects. She's also wiring grapevines, growing in pots in her laboratory.
The little leafhopping insects complete the circuit for the low-level current when they puncture the grapevines with their tube-like mouth parts, to suck the plants' sap. The result? Backus can zero in on the minute-by-minute action of these attacks.
Glassy-winged sharpshooters can transmit a deadly plant bacterium, Xylella fastidiosa, into plants during feeding. This microbe can live in the sharpshooter's gut without harming the insect. But when Xylella moves from a sharpshooter into a plant, the bacterium can form colonies, or clusters, that may eventually shut off the flow of water in the hapless grapevines. Severely infected vines usually die within a year or two after they're attacked.
Backus is analyzing the patterns of electrical waves, somewhat like electrocardiograms, that her instruments record as the sharpshooters feed hungrily. From these charts, Backus intends to piece together new clues about exactly when, how, and how quickly the Xylella microbes in the insect's gut get dislodged and shuttled into the vine.
She also plans to use her electrical system to develop a method for easily pinpointing superior grapevines that are resistant to the insect and bacterium.
When X. fastidiosa attacks grapevines, the infection that results is known as Pierce's disease. Southern California winegrape vineyards were hit hard with this disease in the 1990s soon after the sharpshooter first appeared in the state.
Backus is based at the ARS San Joaquin Valley Agricultural Sciences Center in Parlier, near Fresno. An article in the September 2003 issue of the monthly magazine Agricultural Research tells more about her investigations and those of her Parlier colleagues. The magazine article is posted on the World Wide Web at: http://www.ars.usda.gov/is/AR/archive/sep03/insect0903.htm