Field bioefficacy, phytotoxicity and residue dynamics of the insecticide flonicamid (50 WG) in okra [Abelmoschusesculentus (L) Moench]

Abstract

In India, sucking pests including leafhoppers (Amrasca biguttula biguttula Ishida) and whitefly (Bemisia tabaci Gennadius) cause considerable economic damage to okra cultivation. This study reports the results of field experiments evaluating the bioefficacy, phytotoxicity, and residue dynamics of sprays of flonicamid 50 WG in okra (Abelmoschus esculenta (L.) Moench) crops. Of three doses (50, 75, 100 g a.i ha-1) tested, applications at 75 g a.i ha-1 were equally effective in controlling both leafhoppers and whiteflies with a higher marketable fruit yield of okra under open field conditions. Flonicamid also reduced population of the pest by >85% when compared to untreated controls after three rounds of foliar application at an interval of 10 days. Applications of flonicamid 50 WG did not cause any phytotoxic symptoms. It was also safe to the natural enemies (spiders and rove beetles) prevailing in the okra ecosystem. Initial deposits of flonicamid in okra fruits when applied at the rate of 75 and 150 g a.i. ha-1 were dissipated with half-lives of 3.0 and 3.5 days. Recommendable pre-harvest intervals (PHI) are 16 and 20 days, respectively. The dietary exposure of the measured residues was lower than the maximum permissible intake (MPI) of 0.576 mg person-1 day-1 on all the sampling days at both the doses. These findings are useful in deciding the spray schedule of flonicamid for effective management of sucking pests in okra crop assuring food safety.