Effect of Seasonal Variation on Life Table of Brown Plant Hopper Nilaparvata lugens Stål on Rice Plant in Eastern India

3 Abstract: The seasonal variation on life table of the brown planthopper Nilaparvata lugens Stal(BPH) in Eastern India indicated that the net fecundity rate (R ) is higher in rainy season (79.24) than winter (36.43). o Identical trends of the net reproductive rate (R ) and intrinsic rate of increase (r ), finite rate of increase were t m observed as 31.51 and 0.1286023, 1.1372370 in rainy/kharif season and 9.38, 0.0702774, 1.0728057 in winter respectively. Although the weekly multiplication (r ) of BPH is higher in rainy/ kharif (2.4601354) than winter/ w rabi (1.66469120) but the mean length of generation (T) and doubling time of population (DT) were lower in rainy/ kharif (34.00,5.38) than winter/ rabi as recorded 51.16, 9.86 in the plains of west Bengal during 2010-2011. Likewise the instars wise life table study also showed that the maximum234 eggs were laid by single female of which ultimately 96 adults were produced after 23 days during the month of October and November 2010 (from 14 th October to 10 November2010). Different mortality factors causes 23.50%,17.87%, th 21.76%,and7.82%,and7.76%and 2.0 % death on egg, first, second, third, fourth, fifth instar stages of this insect respectively. Among the different factors so far recorded in side the laboratory the unhatched egg, mechanical injury during coming out through the slit, dispersal, some spider, wrong selection of hostsite particularly the initial settlement on dried part of the tiller were predominant.