Effect of Weather Parameters on the incidence of different life stages of a serious pest H. vigintioctopunctata (Fab.) on Brinjal in Chennai locality, India

The pest population of H. vigintioctopunctata varies from region to region based on their climatic conditions and shows different peak activity in different locations. The present study was carried out to know the actual infestation rate of Epilachna population and effects of weather parameters on the growth of its population. For this study, a well-designed pesticide free plot was formulated and its major host plant S. melongena variety was grown well. Different stages of pest population and its relationship associated with weather parameters were also noted. The peak incidence of mean egg population was 14.83 when the mean minimum and maximum temperatu¬¬re, both morning and evening relative humidity and weekly pressure were recorded as 29.5oC, 39.5oC, 61.8%, 56.4 % and 1007mbar. When the peak incidence of mean grub population was 25.80, the mean weather parameters were 31.0 oC, 39.8 oC, 50.5%, 44.5% and 1003mbar respectively. Similarly, when the peak incidence of the mean pupal population was 4.86, the mean weather parameters were 30.2 oC, 35.4 oC, 52.5%, 48.7%, 1005mbar. Likewise, when the peak incidence of the mean adult beetle population was 12.5, the mean weather parameters were 30.2 oC, 38.1 oC, 53.2%, 48.7% &1005mbar. Thus, from this study, the different life stages of Epilachna beetle is positively correlated with (minimum, maximum and mean) temperature and negatively correlated with (morning, evening and mean) relative humidity and mean pressure.