Effect of weather parameters on population dynamics of Sorghum shootfly, Atherigona soccata

Sorghum [Sorghum bicolor (L.) Moench] is one of the most important cereal crops in the world and in India. The yield of sorghum is being affected by a wide variety of biotic and abiotic constraints. Among the biotic constraints shoot fly is one of the important and destructive pests which is highly influenced by weather. An investigation on the population dynamics of shootfly was undertaken during Rabi, 2016-17 and 2017-18 with sixteen treatment combinations (with four varieties and four sowing windows) and three replications. The design adopted was Split Plot. Higher was the egg count (2.61) during 2016-17 compared to 2017-18 (2.84). Egg counts were higher in Phule Maulee variety followed by Phule Chitra, Maldandi and Phule Vasudha. The correlation analysis with weather parameters revealed significant positive correlation with egg count of with the maximum temperature during both the years, 2016-17 (0.890*) and 2017-18 (0.963**). The shoot fly infestation increased gradually with the delayed sowing windows. A higher per centage of dead hearts was observed in the 41st MW (Meteorological Week) sowing window in the variety, Phule Maulee (23.0 and 21.0) during 2016-17 and 2017-18 respectively. Correlation made between per cent dead hearts with weather parameters at 14 DAE revealed negative association (0.964*) of dead heart infestation with maximum temperature as well as minimum temperature (-0.928*)during 2017-18 also shown with the per cent dead hearts during 2016-17. Higher temperatures are increasing the egg count due to increased fecundity but negatively affecting the dead heart due to increased mortality in adults and eggs.