PJB-2017-514
TOXICITY POTENTIAL OF NEEM EXTRACTS AGAINST PLUTELLA XYLOSTELLA (LEPIDOPTERA; PLUTELLIDAE) AND ITS NATURAL ENEMY, DIADEGMA SPECIES
Hayat Zada
Abstract
The present study was conducted to assess different concentrations of azadirachtin against 3rd and 4th instar larvae of P. xylostella and to determine their effects on natural enemy, Diadegma sp. Four different concentrations (0.31, 0.50, 0.60 and 1%) of azadirachtin were evaluated in the choice and non-choice tests methods. In the choice test, the LC50 value for the 3rd instar larvae were 0.66, 0.41 and 0.37 �g/ml on day 1st, 2nd and 3rd, respectively. Similarly the LC50 values for the 4th instar larvae were 0.55, 0.34 and 0.34 �g/ml after 24, 48 and 72 hours of treatment, respectively. Descending order of toxicity for azadirachtin was observed in no choice method. The LC50 values for the 3rd instar larvae in no choice test were 0.63, 0.32 and 0.29 �g/ml on 24, 48 and 72 hours of treatment, respectively. Further The LC50 value for the 4th instar larvae in no choice test were 0.52, 0.36 and 0.31 �g/ml on day 1st, 2nd and 3rd respectively. Maximum repellencies for 3rd (95%) and 4th instar larvae (90%) were noticed at 1% concentration. Highest mortalities of Diadegma sp were recorded for 1% concentration which started decreasing with decrease in tested concentrations. High LC50 values (4.91 and 1.63ppm) were recorded for Diadegma sp after 24 and 48h exposer time. Likewise, maximum adults of Diadegma sp emerged from pupae in lowest concentration 0.31% which increased with increase in concentration. Concluding, for better management, concentration of azadirachtin should be optimized with Diadegma sp.
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