Effect of selected insecticides on Homalodisca coagulata (Homoptera : Cicadellidae) and transmission of oleander leaf scorch in a greenhouse study
Homalodisca coagulata (Say) is a recent introduction to California. It is known to spread a strain of the bacterium Xylella fastidiosa Wells, Raju, Hung, Weisberg, Mandelco-Paul & Brenner that induces oleander leaf scorch disease in oleander, Nerium oleander L. Oleander leaf scorch is lethal to oleander and threatens to decimate one of the most important landscape shrubs in California. Towards developing a management strategy for H. coagillata-spread oleander leaf scorch, we documented the affects of selected insecticides on H. coagulata mortality, feeding behavior, and disease transmission in a greenhouse study. Oleanders treated with fenpropathrin, fenpropathrin + acephate, and imidacloprid caused significant mortality to caged H. coagulata within 4 h of exposure. Within 24 h, these pesticides caused nearly 100% mortality 3 wk after treatment. In other experiments, acetamiprid and fenpropathrin treatments reduced time spent feeding and total time on plants. H. coagulata on fenpropathrin-, acetamiprid-, and imidacloprid-treated-oleander died in less than 13 min on average. Oleander leaf scorch transmission by H. coagulata was blocked by applications of foliar-applied acetamiprid, and soil-applied imidacloprid and thiamethoxam.