Effect of Lethal and Sub-lethal Concentrations of Some Biopesticides and Insecticides on the Larval Longevity and Fecundity of Potato Tuber Moth, Phthorimaea operculella (Zeller)

The effect of lethal i.e. LC50 and sub-lethal concentrations i.e. LC25 and LC12.5 of Achook (0.0041%, 0.0021%, 0.0012%), Bacillus thuringiensis (Berliner) var. kurstaki (0.0380%, 0.0716%, 0.0101%), Beauveria bassiana Balsamo-Vuillemin (0.2208%, 0.0789%, 0.0382%), λ-cyhalothrin (0.0006%, 0.000025%, 0.000014%) and cypermethrin (0.0016%, 0.00069%, 0.00038%), respectively was evaluated on the larval longevity and fecundity of Phthorimaea operculella (Zeller). Maximum larval developmental period was observed at LC50, of 8. thuringiensis (14.23 days) followed by 8. bassiana (13.57 days) and Achook (12.74 days). The sub-lethal concentrations of these biopesticides (except Achook) slightly prolonged the larval development. However, insecticides viz. λ-cyhalothrin and cypermethrin did not affect the duration of larval development at any of the tested concentrations. Maximum reduction in fecundity was observed at LC50 of λ-cyhalothrin (77.03%), being statistically at par with cypermethrin (76.13%) followed by B. thuringiensis (57.66%), B. bassiana (51.35%) and Achook (26.12%).