Fitness Costs Associated With Insecticide Resistance in Populations of Homalodisca vitripennis Germar (Hemiptera:...

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important vector of bacterial Xyllela diseases throughout the southern and southwestern portions of the United States. Strong insect control measures, such that population densities of the insect vector are significantly reduced, are often necessary to limit the spread of Xylella fastidiosa. Glassy-winged sharpshooter populations within the Central Valley of California have developed a high resistance to imidacloprid (resistance ratio greater than 3,200) and tolerance to pyrethroids (ratio of less than 10) due to frequent applications of these materials. The purpose of this study was to determine the potential effects of insecticide resistance upon a variety of sharpshooter life history parameters associated with reproductive fitness. Our results indicate that individuals from susceptible populations of glassy-winged sharpshooters exhibited significantly higher fecundity and longer adult lifespans than those from the resistant populations. Additionally, resistant individuals were on average slightly larger than susceptible individuals. These results provide a strong indication that resistance to neonicotinoids imposes a reproductive fitness cost in an insecticide-free environment.