The toxicity of flonicamid to cotton leafhopper, Amrasca biguttula (Ishida), is by disruption of ingestion: an electropenetrography study.

Abstract

The cotton leafhopper, Amrasca biguttula, is one of the most destructive pests of cotton in Asia. This species is thought to cause damage by injecting enzymatic saliva into various, presently unknown, cotton tissues and ingesting the resulting macerate. Flonicamid is a novel systemic insecticide used to control the cotton leafhopper; however, its mode of action is unknown. The mechanism of action of flonicamid on cotton leafhopper was investigated using electropenetrography (EPG). EPG recordings revealed six waveforms, i.e. Np (non-probing), A1 (channel cutting), A2, A3, A4, A5 and A6. Waveforms A2 and A3 probably represent active ingestion with (A2) and without (A3) simultaneous watery salivation. The meanings of A4, A5 and A6 are presently unknown, but minor in duration. Flonicamid significantly increased the mean duration of non-probing events and strongly inhibited ingestion by treated insects, which resulted in the slow death of leafhoppers. Inhibition of ingestion was dose dependent, and near-complete suppression was observed when the flonicamid concentration was increased to 10 000 mg L-1 . We propose that starvation caused by inhibition of active ingestion is the mechanism of toxicity for flonicamid. This knowledge could aid in applicability and use of this new insecticide for field management of leafhopper populations. © 2016 Society of Chemical Industry.