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 LC_12.5 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%).