Relative survival and detoxification enzyme activity in Dysdercus koenigii (Hemiptera: Pyrrhocoridae) exposed to β-cyfluthrin alone and its nanometric emulsion

Abstract

Dysdercus koenigii, a global cotton pest, inflicts significant crop losses via sucking the moisture and oil contents from leaves and seeds. The growing environmental hazards with conventional pesticides have led to the exploration of nanotechnology to formulate alternative products and nanoemulsions as suitable insecticide delivery vehicles for target pests. We formulated nanoemulsions using β-cyfluthrin (a pyrethroid) and DMSO (Dimethyl sulfoxide) in 1:2, 1:4, 1:6, 1:8 and 1:10 proportions. The nanoemulsions (NE) were characterized morphologically and biophysically (size, pH, viscosity, PDI and zeta potential) by Transmission Electron Microscopy, Dynamic Light Scattering and Zeta Potential Analyzer. Each NE was transparent, stable, had 11.4–174.1 nm droplet size and, optimal PDI and zeta potential. The spherical and monodispersed 1:2 β-cyfluthrin + DMSO NE was found as the most optimal formulation inducing 100% mortality in D. koenigii fifth instars after 24 h; the NE (LD₅₀ = 3.536 mg/L) displayed 44% higher efficacy than the β-cyfluthrin alone (LD₅₀ = 5.059 mg/L). The LD₅₀ dose of the 1:2 NE enhanced the activity of α-esterase, β-esterase, glutathione-S-transferase, and acetylcholinesterase in nymphs in comparison with β-cyfluthrin alone. The β-cyfluthrin nanoemulsion can act as a potential tool to manage D. koenigii after thorough field assessment and evaluation of the impact on non-target organisms.