Effects of temperature on the flight activity of Graphocephala atropunctata (Hemiptera : Cicadellidae)

Graphocephala atropunctata (Signoret) is the principal vector of Xylella fa stidiosa (Wells, Raju, Hung, Weisberg, Mandelco-Paul and Brenner), the bact erium that causes Pierce's disease of grapevine in coastal California. Moni toring the activity of G. atropunctata in the early spring is important for timing insecticide sprays and assessing the potential for disease spread t o adjacent vineyards. Trapping studies with yellow sticky traps over 3 yr i n Napa Valley, CA, established a significant correlation between early spri ng trap catch and temperature. Sticky trap catches of G. atropunctata occur red in the springs of 1996-1998 only when temperature was greater than or e qual to 14.5 degrees C. In 1997 and 1998, the degree-hours (>14.5 degrees C ) per day from sunrise to sunset during March and April, but not in May, co rrelated significantly with trap catches. The temperature threshold of 14.5 degrees C in the early spring can be used to improve the timing of insecti cidal applications aimed at reducing G. atropunctata populations in vineyar ds affected by Pierce's disease.