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.