2019 Volume 101 Issue 6 Pages 272-277
Japanese oak wilt disease is caused by fungi, which are brought by Platypus quercivorus into the trunk, hinder water supply by filling vessels with its hyphae and then weaken/kill trees. To evaluate the regeneration of Quercus phillyraeoides stands damaged by Japanese oak wilt disease by cutting survived trees, we investigated the effects of infection and gallery formation by P. quercivorus on sprouting success of Q. phillyraeoides. We investigated gallery density and the proportion of xylem discoloration of stumps, and evaluated the sprouting success 1 year and more than 5 years after cutting in two stands in Wakayama Prefecture, Japan. Although there were no significant effects of gallery formation on individual-level mortality rates both 1 or more than 5 years after cutting, the individual-level mortality rate more than 5 years after cutting was larger than that 1 year after cutting. Moreover, there were no significant effects of gallery formation on number and size of sprouts both 1 or more than 5 years after cutting. The number of sprouts 1 year after cutting decreased as increasing in the gallery density. However, gallery density and the ratio of xylem discoloration were positively correlated with stump diameter, which is known to be one of the factors decreasing the sprouting success of Q. phillyraeoides. Therefore, we were not be able to quantify the net effect of the gallery formation on sprouting success of Q. phillyraeoides. In summary, cutting of survived trees of Q. phillyraeoides after attacks of P. quercivorus contributes to regeneration of the stand by sprouting, because most individuals can survive and generate sprouts.
