Experimental release of adult Dastarcus helophoroides (Coleoptera: Bothrideridae) in a pine stand damaged by pine wilt disease: Effects on Monochamus alternatus (Coleoptera: Cerambycidae)

摘要

I examined the effect of the parasitoid Dastarcus helophoroides (Fairmaire) on Monochamus alternatus Hope in Pinus densiflora Sieb. et Zucc. trees that had been killed naturally by pine wilt disease. Selected trees received either released D. helophoroides adults (treated trees) or no treatment (control trees). Vertical (within-tree) and horizontal (among-tree) movement of the released D. helophoroides adults was examined to elucidate their dispersal ability in a damaged pine stand. The release of D.helophoroides clearly had a detrimental effect on M. alternatus survival; M. alternatus mortality was 76.3% in 2002, 84.6% in 2003, and 57.2% in 2004 in treated trees, which was significantly higher than that in control trees (18.8%, 5.3%, and 26.7%, respectively). No parasitism of M alternatus by dispersing D. helophoroides adults was observed on control trees in 2002 and 2003, but it was 16.7% in one of six control trees located 265 m from the nearest treated tree in 2004. No M. alternatus were parasitized in the other control trees, even in the vicinity of treated trees. Two adults that were released in May 2003 remained at the study site were collected in November 2003. Although parasitism by D. helophoroides released onto stems 1.2 m above the ground was observed up to 11 m in treated trees, both the percentage of parasitism and the mortality of M. alternatus decreased with increasing height in the tree.