Feeding response of the cotton aphid,Aphis gossypii, to sublethal rates of flonicamid and imidacloprid

Abstract

AbstractThe cotton aphid,Aphis gossypiiGlover (Hemiptera:Aphididae), is an important sap‐sucking pest of many plants, including melons and peppers. This study was conducted to determine the effects of sublethal exposure to flonicamid and imidacloprid and the mechanisms by which these insecticides affect the feeding behavior ofA. gossypii. The median lethal concentrations (LC50) of flonicamid and imidacloprid for adultA. gossypiiwere 2.40 and 1.92 mg l−1, respectively. The lower lethal concentrations of flonicamid were 1.01 mg l−1(LC30) and 0.29 mg l−1(LC10), and those of imidacloprid were 0.82 mg l−1(LC30) and 0.24 mg l−1(LC10). The developmental period ofA. gossypiinymphs atLC30was 3.6 days for both insecticides, which was shorter than that of the untreated controls (4.2 days). Longevity and total fecundity ofA. gossypiiadults were decreased at the sublethal concentrations of both insecticides. The lowest net reproductive rate was observed inA. gossypiitreated with theLC30of flonicamid. Feeding behavior analyses using an electrical penetration graph showed that sublethal concentrations of flonicamid and imidacloprid had significant effects on the duration of phloem ingestion. Higher doses of flonicamid induced starvation by inhibiting phloem ingestion, whereas imidacloprid acted as a contact toxin rather than an inhibitor of feeding behavior.