Entomopathogenic soil bacteria as biocontrol agents against Spodoptera litura (Fab): A sustainable approach

Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), commonly known as the tobacco caterpillar, is a polyphagous pest found worldwide, causing considerable damage to a variety of agricultural crops. The overuse of chemical insecticides against S. litura has led to the development of resistance, residue problem and ecological imbalance. To address these issues, sustainable and eco-friendly alternatives like microbial control has emerged as a key strategy in integrated pest management. Therefore, the present study was undertaken to assess the insecticidal properties of soil bacteria as potential biocontrol agents against S. litura. Among the screened bacteria, Planococcus sp. (KIC5), Rhodococcus sp. (MG1) and Comamonas sp. (C2) caused 82, 80 and 78 % mortality respectively, compared to 8 % in control S. litura larvae treated with leaves dipped in PBS only. Besides larvicidal activity, these bacteria also prolonged the overall development period with a prolongation of 5.63 days due to MG1, decreased adult emergence and caused morphological abnormalities in S. litura. A remarkable effect was also observed on nutritional indices of S. litura larvae in the form of decreased relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and altered approximate digestibility (AD). The significant adverse effects of KIC5, MG1 and C2 on various biological and nutritional parameters of S. litura indicate their potential as effective biocontrol agents against S. litura.