The experiment was conducted at Main Agricultural Research Station, Dharwad during 2004-05 and 2005-06. The rosette flowers in Bt and non-Bt cotton had non-significant relationship with all weather parameters. Whereas, number of pink bollworm larvae had positively significant with maximum temperature and negatively significant with rest of weather parameters. Similarly green boll damage exhibited positively significant relationship and negatively significant with other parameters. The number of exit holes had positively non-significant relationship with maximum temperature and negatively significant with rest of weather parameters in Bt and non-Bt cotton. The mean per cent rosette flowers in Bt cotton was significantly less (3.03%) compared to non-Bt cotton (7.25%). In Bt and non-Bt cotton, the mean green boll damage was significantly lower (11.92%) compared to non-Bt cotton (28.15%).