Abstract
Bt transgenic cotton, is being a vital part of a pest management program, effectively controls Helicoverpa armigera. However,
the success of Bt technology depends on the persistent vulnerability of target pests to the Bt insecticidal proteins. The baseline
susceptibility of H. armigera larvae was determined for first, second, and third instar larvae field collected from three locations,
Faisalabad, Multan and Bahawalpur, and from a known susceptible laboratory population in 2013 and 2014.The LC50 ranged
from 0.123 to 1.026 μg/ml, 0.148 to 1.675 μg/ml, and 0.210 to 2.761 µg/ml, for first, second and third instar larvae, respectively.
The population of Bahawalpur was 8.34, 11.32 and 14.71-fold more resistant than a susceptible population for first, second,
and third instar larvae, respectively. The population from Multan was 5.54, 7.44 and 8.99-fold more resistant that a susceptible
population for first, second, and third instar larvae, respectively. The population from Faisalabad was 4.08, 4.88 and 5.23-fold
more resistant than a susceptible population for first, second and third instar larvae, respectively. The MIC50 was 0.003 to 0.006
µg/ml, 0.009 to 0.088 μg/ml, and 0.014 to 0.206 µg/ml for first, second and third instar larvae, respectively. The Bahawalpur
population was the most resistant followed by the population from Multan, and the population from Faisalabad had the lowest
amount of Bt insecticidal resistance. The trend in lethal concentration found at the three locations in 2013 was found in the
samples taken in 2014.
