Behavioral and hormetic effects of the butenolide insecticide, flupyradifurone, on Asian citrus psyllid, Diaphorina citri

Abstract

Huanglongbing (HLB) or citrus greening is an economically important disease of citrus associated with the bacterium ‘Candidatus Liberibacter asiaticus’. The pathogen is transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama. Currently, insecticide management of D. citri and removal of infected trees are the only means of decreasing HLB infections. Therefore, with continuous use of insecticides, resistance is one of the most important problems facing citrus production. Flupyradifurone is a new generation butenolide insecticide that has been shown to deter insect feeding and reduce pathogen transmission. We determined the concentration-mortality response of D. citri to flupyradifurone. We also quantified sublethal effects of flupyradifurone on D. citri feeding, settling, flight behaviors, as well as, fecundity of females. We found that after 24 and 48 h of exposure, the LC50 was 0.39 ng/μl (0.16–0.82) in a bottle bioassay and 10.43 ng/μl (2.07–55.87) in a leaf dip bioassay, respectively. D. citri that fed on citrus leaves treated with 0.001, 0.02, 0.39, 8.25 and 130.13 ng/μl solution of flupyradifurone excreted significantly less honeydew (8–83%) compared with a negative control; feeding inhibition occurred in a concentration dependent manner suggesting an antifeedant effect of flupyradifurone. There was no effect of flupyradifurone on D. citri settling behavior at 24 and 48 h after leaf treatment. However, there were significantly fewer adults on treated leaves at 72 h after treatment compared to untreated leaves. D. citri exposed to sublethal concentrations of flupyradifurone initiated flight at greater frequency than negative controls. D. citri exposed to sublethal concentrations (LC10 and LC25) of flupyradifurone laid more eggs than those treated with the negative control. Exposure to lethal and sublethal concentrations of flupyradifurone induced hormesis in D. citri with respect to fecundity. Our data indicate that flupyradifurone may be a useful tool for managing D. citri; however, unexpected sublethal effects must be considered when integrating this chemistry into management programs.