author(s)
MR Thakur, BA Gudade and VM Bhale

abstract
This experiment elucidates effect of agronomic intervention viz., spacing and fertilizer levels and abiotic factors on bollworms infestation in Bt and non-Bt cotton. The investigation was carried out during 2008-09 and 2009-10 at Cotton Research Unit, Akola, Maharashtra, India. The experiment comprises two cotton hybrids viz., Bt and non-Bt of same genotype NCS 145, two spacings viz., 90 × 60 cm and 90 × 45 cm and three NPK levels viz., 50:25:25 kg NPK ha^-1, 62.5:31.25:31.25 kg NPK ha^-1 and 75:37.5:37.5 kg NPK ha^-1. The experiment was laid out in split plot design with four replications. The results revealed that the Bt cotton hybrid suppressed bollworm and loculi damage in fruiting bodies and recorded higher seed cotton yield than non-Bt. Cotton sown at closer spacing of 90 × 45 cm was more susceptible to bollworm infestation but recorded higher seed cotton yield over 90 × 60 cm. Bollworm infestation, loculi damage and seed cotton yield showed linear response to fertilizer levels. The percent bollworm infestation in non-Bt cotton exhibited positively significant relationship with abiotic factors viz., minimum temperature, morning and evening relative humidity and rainfall. Whereas maximum temperature and BSH had non-significant positive and negative relation, respectively.