The insecticidal activity of the entomopathogenic fungus Beauveria amorpha (strain HpBa-1) to larvae of the yellowish elongate chafer, Heptophylla picea was estimated under various temperature conditions. High mortalities were obtained and the mortalities of H. picea rose rapidly at 25°C and 20°C. Insecticidal activity of HpBa-1 was observed at 15°C and 10°C and infection of the fungus resulted under these temperatures. HpBa-1 showed little infectivity at low temperatures under the field conditions. Hence, HpBa-1 recovered infectivity when the temperature increased. These results suggest HpBa-1 is useful as a microbial control agent against larvae of H. picea.