Seasonal changes in the infection of pupae of the beech caterpillar, Quadricalcarifera punctatella (Motsch.) (Lep., Notodontidae), by Cordyceps militaris Link (Clavicipitales, Clavicipitaceae) in the soil of the Japanese beech forest

Abstract

AbstractThe entomopathogenic fungus, Cordyceps militaris, is considered to be an important factor in suppressing population explosions of the beech caterpillar, Quadricalcarifera punctatella. The number of fruit bodies produced by the fungus was counted in a natural beech forest and parasitism was evaluated by burying lab‐reared pupae of the insect in the soil. Seasonal changes in infection rate in the ground and the corresponding number of fruit bodies were compared. The emergence curve of fruit body production exhibited an L‐shape with a peak in late July. The fruit body of C. militaris lasts for about two weeks and appears from late July to early September. The rate of infection was found to change seasonally: it was highest in early August when the number of fruit bodies was at a peak, then decreased gradually until the following summer. From an epizootiological viewpoint, the results suggested that the fruit body plays a role in enhancing the infection rate of the fungus.