Effect of exposure method to Beauveria bassiana and conidia concentration on mortality, mycosis, and sporulation in cadavers of Chilo partellus (Lepidoptera: Pyralidae)

The effects of exposure methods, conidial concentrations, and temperature on mortality, mycosis and sporulation in second instar Chilo partellus cadavers infected by Beauveria bassiana was investigated in laboratory studies. Larvae directly sprayed with conidia, exposed to conidia-treated leaves, and dipped into conidial suspension resulted in high mortality (98-100%). The longest LT50 (3.5 days) and days to mortality (2.6 days) were observed in the treated-leaves exposure method. The shortest LT50 (1 day) and days to mortality (1 day) were recorded for the dipping method. With increasing conidial concentrations, there were decreasing LT50 and days to mortality. Larvae exposed to treated leaves and larvae directly sprayed with conidial suspensions produced high mycoses in cadavers. Exposure of larvae to treated-leaves resulted in high sporulation. At lower concentrations of conidia, both mycosis and sporulation in cadavers were high. The optimum temperature for mycosis was 20 and 15 degrees C for sporulation.