Insecticidal potential of diatomaceous earth against Callosobruchus maculatus (Coleoptera: Chrysomelidae) infesting stored cowpea, Bambara groundnut and soybean in the Sudano-Guinean climatic conditions of Cameroon

Abstract

Diatomaceous earth (DE), derived from fossilized diatoms, serves as an effective alternative to synthetic insecticides for grain protection. This study assessed two DE products, Silico-Sec® and Fossil Shield®, against Callosobruchus maculatus in cowpea, Bambara groundnut, and soybean stored in Cameroon's Sudano-Guinean agro-ecological zone. Four DE doses (0.5, 1, 1.5, and 2 g/kg grain) were evaluated, along with malathion at 0.5 g/kg. Mortality was recorded over six days, and oviposition and F1 progeny production were measured at day seven and at F1 emergence, respectively. Both DE formulations exhibited dose-dependent mortality, with Silico-Sec® achieving 96.5% mortality in cowpea within three days (LD₅₀ = 0.54 g/kg) and Fossil Shield® reaching it in four days (LD₅₀ = 0.33 g/kg) at 2 g/kg. High efficacy was similarly noted for soybean and Bambara groundnut, with both DEs surpassing 95% mortality within 3 day at the highest dose. Furthermore, Silico-Sec® and malathion significantly reduced oviposition on cowpea by 98%, while Fossil Shield® achieved a 71% reduction; analogous trends were observed for F1 progeny inhibition. Silico-Sec® demonstrated efficacy comparable to malathion across all parameters, underscoring its potential as a sustainable option in integrated pest management against C. maculatus in this region of Cameroon.