Monday, December 10, 2007

Distribution and management of citrus in California: Implications for spread and management of glassy-winged sharpshooter, Homalodisca vitripennis

Mark Sisterson,, USDA, San Joaquin Valley Agricultural Sciences Center, 9611 S. Riverbend Ave, Parlier, CA, Rosie Yacoub,, California Dept. of Food and Agriculture, 1220 N Street, Sacramento, CA, Greg Montez,, University of California, Riverside, Dept. of Entomology, Riverside, CA, Beth Grafton-Cardwell, University of California-Riverside, Department of Entomology, Parlier, CA, and Russell L. Groves,, University of Wisconsin, Entomology, 537 Russell Laboratories, 1630 Linden Drive, Madison, WI.

The epidemiology of Pierce’s disease of grape in California has changed over the last 10 years due to the introduction of an exotic vector, Homalodisca vitripennis. Although this insect is highly polyphagous, citrus is considered a preferred host of H. vitripennis and proximity to citrus has been implicated as a causal factor in recent epidemics of Pierce’s disease in southern California caused by H. vitripennis. As citrus is a key host in the seasonal population biology of H. vitripennis in California, a detailed knowledge of the distribution and management of citrus in relation to grape is needed. Analysis of data on the area planted to these two commodities indicates that only 5 counties in California concomitantly grow >1,000 hectares of grape and >1,000 hectares of citrus: Riverside, Kern, Tulare, Fresno, and Madera Counties. Within these 5 counties, the proximity of grape to citrus was greatest for Riverside County compared to the other four counties. The use of carbamates, organophosphates, and pyrethroids as part of the typical citrus pest management program for the control of key insect pests was compared among the same five counties. These insecticide classes were investigated because each is known to kill H. vitripennis. The use of such broad-spectrum insecticides was lowest in Riverside County compared to the other four counties. Results are discussed in context of previous outbreaks of Pierce’s disease in Kern and Riverside Counties.

Species 1: Hemiptera Cicadellidae Homalodisca vitripennis (glassy winged sharpshooter)