Influence of abiotic factors on leafhopper and whitefly population buildup in BT cotton hybrids

The Bt cotton is highly effective against the target lepidopteran bollworms, however, the sucking insect pests have appeared as key pests. Therefore, to understand the genotypic and environmental effects on the population build up of sucking pests, 28 Bt cotton hybrids were evaluated under unsprayed conditions during the 2008 and 2009 cropping seasons. During the 2008 cropping season, the mean leafhoppers population was maximum (1.31 leafhopper/3 leaves) in RCH 569 BG II followed by NCS 913 Bt (1.27 leafhopper/3 leaves) being lowest in SDS 9 (0.49 leafhopper/3 leaves), while for whitefly it was maximum in Tulsi4 BG II (1.13 whiteflies/3 leaves) followed by KDCHH 441 BG II (1.11 whiteflies/3 leaves) and minimum in ANKUR 2534 Bt (0.41 whiteflies/3 leaves). During 2009 cropping season, the population of leafhoppers was maximum in NCEH 6 (2.17 leafhopper/3 leaves) being minimum in MRC 7031 BG II (1.21 leafhopper/3 leaves), while for whiteflies it was maximum in MRC 6025 Bt (5.46 white flies/3 leaves) and minimum in NCS 950 Bt (0.98 white flies/3 leaves). The evaluation of Bt cotton hybrids during both 2008 and 2009 cropping seasons indicated increased trend of leafhopper and whitefly populations across test Bt cotton hybrids. Furthermore, the studies also exhibited increasing trends in number of both the sucking pests during July to September, and decline in their population thereafter. The correlation analysis indicated significantly positive correlation between leafhoppers and minimum temperature during 2008, while during 2009 it was significantly negative with maximum temperature and positive with morning relative humidity for both leafhoppers and whiteflies.