Efficacy of Coragen 20 SC against Lepidopteran Pest in Greengram and Its Compatibility with Bacillus thuringiensis Isolates
Background: Green gram, Vigna radiata (L.) R. Wilczek is third most important pulse crop cultivated in India. The two key insect pest viz., pod borer, Helicoverpa armigera Hubner and Tobacco leaf caterpillar, Spodoptera litura Fabricius inflicts heavy yield loss in greengram. As these are polyphagous insect pest and the crop is a short duration crop, immediate management strategy such as chemical control is very much essential to check its yield loss. The current study reports the efficacy of novel insecticide i.e. Coragen® 20 SC against above cited two insect pest in greengram. Further its effect on non-target insects and its influence on growth and survival of Bacillus thuringiensis were evaluated. Methods: Field experiments were conducted to evaluate the efficacy of Coragen® 20 SC (at four doses viz., 75 ml ha-1, 100 ml ha-1, 125 ml ha-1 150 ml ha-1), chlorpyriphos 20 EC @ 2.5 l ha-1 and emamectin benzoate 5 SG @ 220 g ha-1 against H. armigera and S. litura during kharif 2018 and 2019. Based on larval load per plant, the percent reduction in larval counts was estimated based on Henderson and Tilton method. The benefit cost ratio (BCR) was worked out for each respective year based on seed yield and net returns. Result: Coragen® 20 SC at 125 ml ha-1 and 150 ml ha-1 had resulted in highest percent reduction in larval population over control. Simultaneously, the highest BCR during kharif 2018 (6.29, 4.21) and 2019 (5.95, 5.64) were recorded from above 2 treatments. Further, Coragen® 20 SC showed compatibility with 5 Bt isolates evaluated, i.e Bt growth didn’t inhibited in nutrient agar containing field dose of Coragen 20 SC.