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一、前言近年来,茨城县各地的赤松(Pinusdensiflora)、日本黑松(P·thunbergii)林,由于受松材线虫为害,部分地区发现了松林毁灭的地块。因此,迹地更新是个严重问题。选用对松材线虫抗性强的火炬松(P·taeda L。)作为这种迹地造林树种之一,正在被人们所关心。作为改善平地林经营的一环,1960年在茨城县试栽了一些火炬松林,现存的林分亦很多。在调查松材线虫对火炬松为害状况时,还发现了从来未有记录过的癌肿症状病害。为此,笔者等人在调查该病害危害状况的同时,对其发病原因进行的研究,搞清了由这种未记录过
I. Introduction In recent years, Pinus densiflora and P. thunbergii forests around Ibaraki Prefecture have been found to have destroyed the pine forests in some areas due to the damage caused by pine wood nematodes. Therefore, the track update is a serious problem. The use of P. taeda L., which is highly resistant to pine wood nematodes, is being considered as one of the tree species for this site. As part of efforts to improve the operation of flatlands, some planted Torch Pine forests were built in Ibaraki in 1960, and the existing forest stands are also numerous. In the investigation of pine wood nematode on the status of loblolly pine damage, but also uncovered a never before symptoms of cancer symptoms. To this end, the author et al in the investigation of the disease hazard status at the same time, the incidence of its research to find out by this unrecorded