Abstract: The study was conducted at Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad. There were eight cotton varieties namely, N-K, K-I, K-2, FH-109, MNH-554, N-86, N-98 and CIM-482. The study was conducted to see the effect of abiotic factors against the infestation fluctuation of American bollworm on different nectarid and nectariless cotton varieties under unsprayed conditions. American bollworm infestation on squares and green bolls was maximum on N-98 and CIM-482 in 2nd and last week of September, when the temperature was 32.06 and 30.11oC, relative humidity o ranges from 59.21 and 57.42% and rainfall was only 0.10 and 0.0 mm. The minimum infestation was recorded on nectariless varieties i.e., K-1, N-K and K-2 in the month of August. The results concluded that correlation between infestation and weather factors indicated that temperature and relative humidity affected positively while the rainfall was negatively correlated on different varieties under unsprayed conditions.