Effect of weather parameters on incidence of lepidopteran defoliators on groundnut in Bundelkhand region of Uttar Pradesh

Among two key lepidopteran defoliators viz., tobacco caterpillar, Spodoptera litura and American bollworm, Helicoverpa armigera on groundnut, tobacco caterpillar was first noticed at early stage of the crop growth followed by American bollworm. The incidence of both insect-pests fluctuated under varying weather conditions. Off these, S. litura initiated with mean larval population of 0.21 plant⁻¹ in 31^st standard week and reached its peak (7.01 plant⁻¹) in 39^th SW. However, the larval population of H. armigera initiated with 0.19 plant⁻¹ in 34^th SW and reached to its maximum (5.02 plant⁻¹) in 40^th SW. Among all the meteorological variables, only maximum relative humidity was found significant correlation with larval population of both the defoliators. The maximum temperature, minimum temperature and minimum RH had positive correlation whereas, the rainfall had shown negative correlation with larval population of S. litura. The larval population of H. armigera had positive correlation with max. temp. and max. RH, whereas it had negative correlation with min. temp., min RH and rainfall.