EFFECT OF ABIOTIC FACTORS ON THE EFFICACY OF Beauveria bassiana AND DIATOMACEOUS EARTH AGAINST Rhyzopertha dominica (F.)

The herein reported study was performed to assess the insecticidal efficacy of diatomaceous earth (DE) Concern® and Beauveriabassiana under three levels of temperature (i.e., 25, 30 and 35°C) and three levels of relative humidity (RH; 45, 60 and 75%) against Rhyzoperthadominica (F.). Three dose rates of DE was 200, 400 and 800ppm while for B. bassianawas 1x10^8, 1.5x10^8 and 2x10^8 spores/kg grain that were applied on wheat grains and mortality was noticed after 7, 14 and 21 days after treatment, whereas adult progeny emergence was observed 60 days of post exposure. Results regarding DE have showed thatincrease of temperature and decrease of RH have resulted into significantly increase in adult mortality. Maximum mortality of 74.33% was assessed with a highest tested dose of 800ppm after 21 days exposure at 35°C and 45% RH, progeny development was also greatly suppressed under same conditions. For B. bassiana, efficacy was highly dependent on temperature and RH, as lower level of temperature (25°C) and moderate RH (60%) showed maximum mortality of 82.5% with dose rate of 2x10^8 spores/kg grains after 21 d. Emergence of offspring in fungus treated grains was highly suppressed at 25°C with combination of both 45 and 60% RH whereas at 30 and 35°C significant reduction of progeny was noticed only with 45% RH. The present study divulge that in current scenario of climate change, that alter the patterns of environment, abiotic factors specifically temperature and humidity must be seriously considered when planning an IPM strategy based on the application of B. bassiana and DE Concern®.