Population Dynamics of Mustard Aphid in Relation to Weather Parameters and Effect of Predators on Aphid Population

The experiments were conducted to assess the population dynamics of mustard aphid (Lipaphis erysimi) and its important predators on three dates of sowing at Banda. The occurrence of mustard aphid was started from 52^nd Standard Week (SW) and continued till harvest (12^th SW). The population ranged from 0.15 to 26.31, 0.11 to 259.34 and 0.03 to 305.49 aphids/10 cm central twig/plant, respectively on timely, mid late and late sown crop. Four predators viz., Coccinella septempunctata, Coccinella spp. (unidentified), Cheilomenes sexmaculata and Syrphid fly (Episyrphus balteatus) were recorded at different stages of the crop growth. The population of predators was significantly increased with an increase in the aphid population from 7^th to 10^th SW among the different dates of sown crops. A mixed type of significant level of correlation coefficient had shown among mustard aphid and weather parameters and even the dates of sown crops. The multiple stepwise linear regression equations showed weather parameters greatly influenced the aphid population at timely and mid late sown mustard crops, however the aphid predators were more influenced at mid-late and late sown mustard crops and both abiotic and biotic factors played a vital role in growth multiplication, development and distribution of mustard aphid.