1Department of Entomology, Himachal Pradesh Krishi Vishvavidyalaya, Palampur-176 062, Himachal Pradesh (India).
2Entomologist, HPKV, Regional Research Station, oajaura, Kullu-175 125, Himachal Pradesh (India).
*A part of approved Ph. D. thesis submitted by Surjeet kumar to Himachal Pradesh Krishi Vishvavidyalaya, Palampur, Himachal Pradesh (India).
The biology of laboratory selected malathion-resistant (7.79 times) and endosulfan-resistant (6.59 times) strains of Epilachna vigintioctopunctata (F.) was compared with the susceptible strain. The three strains were derived from the pool of 12 populations collected from different vegetable growing areas of Himachal Pradesh and reared in the laboratory for 9 generations with and without insecticidal selection pressure. The resistant strains had significantly longer incubation period and lower egg viability as compared to the susceptible strain. Total developmental period of the resistant strains was significantly longer than the susceptible strain. Significantly less number of eggs/female were laid by malathion-resistant (331.93) and endosulfan-resistant (328.93) strains in comparison to susceptible strain (391.07). Development of resistance to malathion and endosulfan adversely affected the biotic potential of E. vigintioctopunctata by having significantly longer developmental period and reduced reproductive potential. The resistant strains had become biologically inferior to the susceptible strain.
