Pest management for the glassy-winged sharpshooter, Homalodisca
   vitripennis Germar (Hemiptera: Cicadellidae), in Kern County, California
   relies on the application of insecticides. These treatments have
   contributed to low H. vitripennis field counts since applications were
   initiated in 2001. However, densities have been high in recent years
   despite continued management, prompting efforts to evaluate the
   susceptibility of current populations to insecticides. H. vitripennis
   adults were subjected to bioassays with five commonly applied
   insecticides, and the results were compared to baseline toxicities
   determined in 2002. Two neonicotinoids, imidacloprid and thiamethoxam,
   were evaluated using systemic uptake bioassays. Contact toxicities of
   the neonicotinoid acetamiprid and pyrethroids bifenthrin and
   fenpropathrin were estimated using leaf dip bioassays. Dose-mortality
   responses were analyzed by probit analysis. For each compound, there was
   no significant difference in annual LC50 values determined over 2 yr.
   Compared to baseline toxicities, acetamiprid and bifenthrin were found
   to be significantly less toxic to H. vitripennis.The LC50 values of
   these two compounds increased sevenfold and 152-fold, respectively.
   Tests with the neonicotinoids revealed a trend of decreasing
   susceptibility levels within each season followed by reversion back to
   early season LC50 estimates in the following year. In addition, data
   showed seasonal and site variation in susceptibility to imidacloprid,
   possibly due to differential applications in nearby fields.