author(s)
Deepika Kalkal, Roshan Lal, KK Dahiya, Krishna Rohlania, Dalip Kumar and Arun Janu

abstract
Nineteen genotypes comprising seventeen Bt hybrids, one conventional hybrid and one variety were evaluated during kharif season of 2008-2009 and 2009-2010 for their reaction to bollworms under unsprayed conditions at Cotton Section, Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar. Spotted bollworm infestation remained below economic threshold (ET) in all the genotypes, however, from 34^th week onwards the infestation crossed economic threshold (5% infestation) in non-Bt variety H-1226. On mean basis maximum infestation was recorded in H-1226 (19.47 and 17.95 percent during 2008 and 2009 respectively) whereas minimum infestation was observed in RCH-134 Bt (1.28%) in 2008 and NCEH-6 Bt (0.21%) in 2009. Larval population was ranged from 0.00-4.00 larvae/5 plant in 2008 and 0.00- 4.65 larvae/ 5 plant in 2009. While maximum population was recorded in H-1226 non-Bt (4.00 larvae/5 plant in 2008 and 4.65 larvae/5 plant in 2009) at 40^th standard week. Spotted bollworm population were found significantly negative correlation with temperature, relative humidity and rainfall while positive correlation with sunshine hours.