Weather-mediated Population Dynamics of Tobacco Caterpillar, Spodoptera litura (Fab.), on Clusterbean [Cyamopsis tetragonoloba (Linn.) Taub.]

Abstract

A field experiment was conducted at the Agronomy Farm of S.K.N. College of Agriculture, Jobner, Rajasthan, to assess the weather-mediated population dynamics of tobacco caterpillar, Spodoptera litura (Fab.), on clusterbean during two consecutive Kharif seasons, 2022 and 2023. The crop was raised under field conditions, and larval incidence was recorded weekly from pest appearance until harvest. The incidence of tobacco caterpillar commenced during the third week of August, corresponding to the 33rd standard meteorological week, with 0.04 and 0.12 larvae per plant during 2022 and 2023, respectively. The population reached its peak at 1.92 larvae per plant in the third week of September during 2022 and 1.98 larvae per plant in the second week of September during 2023. Correlation analysis indicated that maximum temperature had a significant positive association with tobacco caterpillar population in both years, with correlation coefficients of r = 0.649 in 2022 and r = 0.592 in 2023. In contrast, minimum temperature, relative humidity and rainfall showed non-significant associations with larval incidence during both seasons. Multiple regression analysis showed that the selected weather parameters collectively explained 55 per cent and 77 per cent of the variation in tobacco caterpillar population during 2022 and 2023, respectively. Stepwise regression further indicated that maximum temperature alone explained 50 per cent of the variation in 2022 and 35 per cent in 2023.