Asian Research Thesis Index

Abstract

Studies were conducted on the sustainable management of whitefly (Bemisia tabaci Genn.) on available genotypes of Bt cotton at Faisalabad during 2005-06. The data obtained was correlated with ambient weather factors to determine the role of abiotic factors in population fluctuation. Various physico-morphic and chemical plant characters were correlated with the population of the whitefly with the aim to find their role in the life activities of the pest on Bt-cotton and sustainable management of whitefly by integrating the safest insecticide to Chrysoperla carnea. The results, during 2005 and 2006 on an average basis, revealed significant difference among genotypes regarding population of whitefly per leaf. On an average basis both the study years FH-114 appeared comparatively resistant showing minimum population of whitefly per leaf i.e. 2.59 while FH-113 showed susceptible trend with maximum population of whitefly i.e. 2.84 per leaf. Significant difference was observed among dates of observation regarding population fluctuation of the whitefly. During 2005, the third week of July showed maximum peak i.e. 4.81 whitefly per leaf. During 2006, the population of whitefly reached to maximum peak i.e. 6.65 per leaf during 3 rd week of September. The study on the population dynamic of the whitefly showed that rainfall during 2006 had negative and significant correlation with the population of whitefly per leaf on BT cotton. Multiple linear regression analysis of variance indicated that minimum temperature was the most important factor. Physico-morphic characters showed significant and positive correlation with the population of whitefly having r-values of 0.613**, 0.428*, 0.660**, 0.716**, 0.486* and 0.725**, respectively. Hair length and thickness of leaf lamina exerted negative and significant effect on the pest population with r-values of -0.654** and - 0.446*, respectively. Hair density on lamina and hair length on midrib and vein showed non-significant effect on the pest population. Multivariate linear regression model for hair density on midrib was found to be the most important plant character which contributed maximum i.e. 42.72% role in population fluctuation of whitefly on BT cotton. The 100R 2 value was calculated to be 85.47 when the effect of all physical plant characters was computed together. Nitrogen percentage in the leaves of BT cotton showed maximum impact i.e. 32.92 percent in population fluctuation of the pest and appeared to be the most important. Study regarding integrating the safest insecticide to Chrysoperla carnea showed that buprofezin has minimum mortality of the pest and proved to be the safest for all three larval instar and pupal and adult stage of C. carnea and Endosulfan proved to be xiiithe most toxic to all life stages of the predator. Whitefly population was decreased by increasing the number of cards and 988 cards/ha integrated with the application of buprofezin showed the best results with minimum population of whitefly and maximum increase in seed cotton yield.

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