The impact of several insecticides against the legume pod borer, Maruca vitrata Fab. (Lepidoptera: Crambidae) on cowpea

Cowpea (Vigna unguiculata), a widely cultivated grain legume in Nepal and a member of the Fabaceae family, faces significant production challenges due to the legume pod borer (Maruca vitrata). This pest is a major threat, limiting both the yield and productivity of cowpea crops. The research was laid out in Randomised Completely Block Design with seven treatments and three replications. The treatments comprise chlorantraniripole 18.5% SC, emamectin benzoate 5% SG, spinotoram 11.7% SC, dimethoate 30% EC, azadiractin 0.07 % EC and BT+ Saccharopolyspora spinosa and control. Chlorantraniliprole demonstrated the highest effectiveness, reducing larval populations to just 0.16 after the fourth application, while achieving the maximum fruit yield of 13 t/ha. Emamectin and spinetoram also performed well, both decreasing larval counts to below 1.0 and producing comparable yields of 12.90 t/ha and 12.89 t/ha, respectively. In contrast, biological treatments, such as Bacillus thuringiensis var. Kurstaki, exhibited moderate success in pest control, resulting in a lower yield of 10.19 t/ha. Azadirachtin and the untreated control plots experienced the highest infestation rates, leading to significantly lower yields of 8.04 t/ha and 4.70 t/ha, respectively. Chlorantraniliprole also proved superior in reducing fruit damage, limiting it to just 1.55%, compared to the high damage rate of 42.04% observed in the untreated control. These findings highlight the strong efficacy of chemical insecticides, especially chlorantraniliprole, in controlling Maruca vitrata infestations and enhancing cowpea productivity. Future studies should focus on integrating biological agents with chemical treatments to minimize environmental impacts and prevent resistance, while maintaining high yields and effective pest control.