Safety of some biopesticides towards ladybird beetles and rove beetle on cowpea, Vigna unguiculata (L.)

Field trials were conducted at the Agricultural Research Station, Faculty of Agricultural Sciences, SOADU, Binjhagiri, Khurdha, during the rainy season of 2022 and winter of 2022-23 to evaluate the safety of five biopesticides on predators in cowpea crops. Four species of ladybird beetles and one species of rove beetle (Paederus fuscipes Curtis) were observed. Among the ladybird beetles, Coccinella repanda Thunberg was the predominant species, accounting 43.84% of the total population, followed by Cheilomenes sexmaculata Fab. (31.51%), Micraspis discolour Fab. (15.07%) and Brumoides suturalis Fab. (9.59%). The treatments included Bacillus thuringiensis var. kurstaki (16000 i.u./ mg) at 1.0 Kg/ha, Beauveria bassiana (108 cfu/g) at 2.5 Kg/ha, Metarrhizium anisopliae (108 spores/g) at 2.5 Kg/ha, Lecanicillium lecani (108 cfu/g) at 2.5L/ha, azadirachtin (300 ppm) at 2.5 L/ha, chlorantraniliprole (18.5% active ingredient) at 0.25 L/ha (chemical check) and an untreated control. All the biopesticides proved to be safe for ladybird beetles and the rove beetle. B. thuringiensis var. kurstaki was the safest, recording only 3.94% and 3.40% reductions in ladybird population five days after application during the rainy season of 2022 and winter of 2022-23, respectively. It was followed by B. bassiana (6.35% and 4.45% reduction), M. anisopliae (8.97% and 7.33% reduction), L. lecani (10.28% and 8.90% reduction) and azadirachtin (19.04% and 26.96% reduction). A similar trend was observed in rove beetle, with respective reduction of 5.07% and 3.79%, 5.67% and 4.92%, 6.87% and 6.06%, 7.76% and 6.82% and 17.31% and 26.14%.