Optimizing sucking pest control in okra: an analysis of flupyradifurone 200 SL effectiveness, phytotoxicity, safety to natural enemies, pollinators and cost-efficiency

Abstract

Whitefly, Bemisia tabaci (Gennadius), and leafhopper, Amrasca biguttulla biguttulla, Ishida, are the major biotic constraints in cultivation of okra, causing considerable economic damage. The present study aims to evaluate the laboratory and field efficacy of butenolide insecticide, flupyradifurone 200 SL against these key sucking pests, its phytotoxicity, safety to natural enemies as well as pollinators and cost-efficiency in okra. Dose probit mortality assays indicated flupyradifurone to be the most toxic and thiamethoxam least toxic to leafhopper and whitefly. Based on the LC₅₀ values for whitefly and leafhopper, flupyradifurone exhibited 11.07 and 2.98-fold difference, respectively, when compared to thiamethoxam. Laboratory bioassays confirmed that the maximum dose of flupyradifurone (250 g a.i. ha⁻¹) had a high level of toxicity to whitefly adults and leafhopper nymphs. Of the three field rates (150, 200, 250 g a.i. ha⁻¹) of flupyradifurone evaluated under open field conditions, application at 250 g a.i. ha⁻¹ was most effective for the control of whitefly and leafhopper population with a high marketable fruit yield in okra. Flupyradifurone reduced the population of whitefly by 71.80 & 76.68 per cent and leafhopper by 82.19 and 80.21 per cent during first and second season, respectively, as compared to untreated control. Furthermore, it was superior and more economical, giving the highest benefit: cost ratio (2.77) than other test insecticides included for comparison. Flupyradifurone application showed no phytotoxic symptoms on the okra crop. Additionally, it was found to be safer to natural enemies i.e. spiders and rove beetles that are prevalent in the okra ecosystem. The Kaplan–Meier survival analysis showed that flupyradifurone was apparently less toxic to honey bees in short-term and long-term exposure assays. These findings will aid in utilizing the flupyradifurone in insecticide window spray schedules and IPM programs for the management of sucking pests in okra.