Seasonal Fluctuation of the Pine Wood Nematode, Bursaphelenchus xylophilus (STEINER et BUHRER) NICKLE (Nematoda : Aphelenchoididae), Transmitted to Pine by the Japanese Pine Sawyer, Monochamus alternatus HOPE (Coleoptera : Cerambycidae)

Abstract

Seasonal fluctuation in numbers of the pine wood nematode, Bursaphelenchus xylophilus (STEINER et BUHRER) NICKLE, transmitted to pine from the bodies of adult Japanese pine sawyers, Monochamus alternatus HOPE, was determined from the simulation model proposed by TOGASHI (1980). Nematodes invaded the pine trees between mid-June to late-July, with the peak invasion in late-June. This peak appeared about two weeks after the number of adult beetles reached maximum. In the study forest, pine trees diseased by nematodes appeared before July 20 and 31 trees died before winter began. The date that a cumulative 50 percent of the trees were diseased was August 11, 56 days after a cumulative 50 percent of the nematodes invaded the pine trees.