Influence of varying temperatures on toxicity of biorationals against diamondback moth, <i>Plutella xylostella</i> L.

Abstract

<p>Effect of various temperatures on the efficacy of five biorationals, viz. <em>Beauveria bassiana</em> (1.15% WP), <em>Metarhizium anisopliae</em> (1.15% WP), <em>Bacillus thuringiensis</em> (0.5% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) in terms of median lethal concentration (LC<sub>50</sub>) value was evaluated against diamondback moth, <em>Plutella xylostella</em> larvae. The toxicity data for biorationals against <em>P. xylostella</em> on the basis of larval mortality revealed that <em>M. anisopliae</em> (1.15% WP), <em>B. thuringiensis</em> (0.5% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) registered higher effectiveness (lower LC<sub>50</sub> value) at 25°C whereas, increase in temperature led to declined efficacy of biorationals; whereas, use of entomopathogenic fungi, <em>B. bassiana</em> (1.15% WP) was most effective at 30°C and revealed lower effectiveness (higher LC<sub>50</sub> value) at 25° and 35° C temperatures. Data on the influence of temperature on toxicity of biorationals to <em>P. xylostella</em> on the basis of adult emergence revealed lowest LC50 value for <em>B. thuringiensis</em> (0.5% WP) at 25°C and the efficacy decreased with increase in the temperature, whereas, <em>M. anisopliae</em> (1.15% WP), <em>B. bassiana</em> (1.15% WP), Azadirachtin (300 ppm) and Spinosad (45 SC) were most effective at 30°C and the higher LC<sub>50</sub> value were evident at temperature above 30°C, indicating the reduced efficacy of biorationals with increase in temperature beyond 30°C or preference for lower temperature regimes under laboratory conditions.</p>