Efficacy of Beauveria bassiana for control of the rice weevil Sitophilus oryzae (L.) (Coleoptera : Curculionidae)

An entomopathogenic fungus, Beauveria bassiana was tested against the rice weevil Sitophilus oryzae. Bioassays were conducted by introducing 25 adult insects on 50 g of B. bassiana mixed rice in glass jars maintained at 28 +/ - 2 degreesC, and 70% RH. Mortality was monitored at five-day intervals unt il 25 days. At higher doses (7.6 log conidia/ml), B. bassiana produced a hi gher percentage of mortality up to 75.8% and F-1 adult emergence was reduce d by 86.2%. At lower concentrations B. bassiana was not effective against S . oryzae. The study stresses the need for higher numbers of conidial inocul ation for maximum mortality.