Synergistic effects of legume intercropping and integrated pest management on fall armyworm management in maize

Abstract

An experiment was carried out at the Agricultural Research Farm, Andro, Central Agricultural University, Imphal, Manipur during kharif 2025 to study the impact of intercropping of maize with legumes along with seed treatment and biopesticide spray against fall armyworm (Spodoptera frugiperda) and productivity of maize. A randomized block design with three replications was employed to test the effect of eight treatments, which included chlorantraniliprole seed treatment, intercropping with ricebean or rajma, and foliar spray of Bacillus thuringiensis, alone or in combination. Infestation increased progressively up to 50 days after planting (58.00% in untreated sole maize) before decreasing towards maturity of the crop. Intercropping of ricebean along with chlorantraniliprole seed treatment and foliar spray of Bt at 25-30 DAG showed the minimum infestation and leaf damage, the highest population of natural enemies (6.10 per plant), the lowest cob damage rating (1.11), the highest grain yield and intercrop yield with 54.81 q ha-1 and 6.14 q ha-1 respectively and the highest B:C ratio (3.17), as compared to untreated sole maize, which recorded the highest infestation (58.00%), the lowest natural enemy population (2.03 per plant), the highest cob damage rating (3.89), the lowest grain yield (27.78 q ha -1) and the lowest B:C ratio (0.61). Legume intercropping on its own accounted for reduced pest infestation and increased natural enemy activity in comparison with sole cropping, but the integration of legume intercropping, seed treatment, and application of biopesticides resulted in additive pest suppression and enhanced biological control. The integrated use of ricebean intercropping, chlorantraniliprole seed treatment, and Bt foliar spray can be used as an alternative approach to manage lepidopteran pests on maize.