ABSTRACT

Investigations were carried out at All India Co-ordinated Research Project (AICRP) on Soybean, Main Agricultural Research Station, University of Agricultural Sciences, Dharwad during kharif 2023. Among 22 genotypes screened for the resistance against defoliators, the genotype SL 1311 categorized as a highly resistant, VLS 105 and AMS 2021-3 as resistant, Himso 1696, DSb 40, NRC 258 and AS 34 were categorized as moderately resistant, whereas JS 335, NRC 259 and NRC 260 were categorized as highly susceptible to defoliators. Correlation studies revealed that biophysical traits such as thicker leaves and higher trichome density were linked to greater resistance and reducing rate of defoliation. In-vitro evaluation of resistance mechanisms of selected promising soybean genotypes confirmed that Spodoptera litura larvae had the lowest feeding efficiency and growth on genotype SL 1311 with least Approximate Digestibility (AD), Efficiency of Conversion Index (ECI) and Efficiency of Conversion of Digested Food (ECD). In choice-based test genotypes SL 1311, VLS 105 and AMS 2021-3 were less preferred by S. litura for feeding as well as for oviposition.
Among soybean based intercropping systems, Soybean + Dill (10:2) and Soybean + Marigold (10:2) systems were successful in decreasing the population of defoliators and per cent leaf damage by improving pest management and boosting soybean growth and yield. These two intercropping systems demonstrated their economic supremacy by achieving the best net returns and B:C ratios. This could be due to the additional plant diversity provided by intercrops, which may serve as alternative hosts or attractants for the larvae, ultimately reducing pest pressure on maincrop. Whereas, the sole soybean recorded the highest per cent leaf damage and lower yields, indicating that it was more vulnerable to defoliator pests when grown alone.