The role of temperature on the pathogenicity of Beauveria bassiana in populations of sawtoothed grain beetle, Oryzaephilus surinamensis (Coleoptera: Silvanidae) fed on stored date fruits

Beauveria bassiana (Balsamo) is one of the promising microbial control agents for the management of Oryzaephilus surinamensis (L.) Death rate, lethal time and survival expectancy were calculated for an infected population of O. surinamensis at 15, 20, 25, 30 and 35 °C. Results showed that the mean death rate under above mentioned temperatures was 0.89, 1.15, 1.40, 1.21, and 1.11 larvae/day, respectively. The values were 0.99, 1.38, 1.47, 1.18 and 1.16 insects/day for adults respectively. LT50s, at the same temperatures, were 7.11, 7.04, 4.82, 6.07 and 6.89 days for larvae and 7.03, 6.31, 4.83, 5.58, and 6.55 for adults, respectively. Survival curves for both larval and adult populations were more similar at 25, 30 and 35 °C compared to 15 and 20 °C. The survival rates in infected populations were low during 3rd and 4th days post inoculation and decreased with a sharp slope toward the end of the experiments under different temperatures. In every case, survival curves were of the 2nd type in which the mortality decreases in a steady linear form.