マツの材線虫病の感染源に関する生態学的研究 (II) : 非激害型アカマツ林分におけるマツノマダラカミキリの生態とその駆除方法について

Abstract

本報告ではマツの材線虫病による非激害型アカマツ林分におけるマツノマダラカミキリ (Monochamus alternatus HOPE) の生態とその駆除方法が検討されている。調査は京都大学農学部附属演習林上賀茂試験地の天然生アカマツ (Pinus densiflora S. et Z.) 林を対象として, 1983, 1984年に行なわれ, その結果は次のとおりであった。マツノマダラカミキリ成虫の羽化脱出は6月13日に始まり7月30日に終った。羽化脱出時の有効積算温量は350日度, 50％脱出時には620日度であった (1984)。枯損木におけるマツノマダラカミキリ成虫の後食痕は新食痕では1 - 3年枝で, 旧食痕は2 - 4年枝で多くみられ, 後食量の多いマツは早期に枯れ症状を示した。マツノマダラカミキリ幼虫の材内への穿入は早期に枯れ症状を示したマツで多かった。マツノマダラカミキリ幼虫の穿入数に対する老熟幼虫数は約50％で, 羽化脱出成虫数は約25％であった。枯損木を秋期 (10月20日) に伐倒し, 薬剤処理したものはマツノマダラカミキリの殺虫効果がたかかった。また, 被害材を割って薬剤処理する方法では極めてたかい駆除効果を示した。被害材の割材化はそれ自体で丸太材の薬剤処理に匹敵する効果を示したことは枯損林, 木が遠隔地や地形的に急峻な場所にあり薬剤処理の困難な場合には非常に有効な手段と考えられる。

The life history of the Japanese pine sawyer, Monochamus alternatus HOPE, a vector of the pine wood nematode, Bursaphelenchus xylophilus STEINER & BUHRER, a pathogen of pine wilt was investigated in 1983 and 1984 at the natural stand of the Japanese red pine, Pinus densiflora S. & Z., in Kamigamo Experimental Forest Station, Kyoto University, where native pine trees are damaged not so severely but killed gradually every year. Several methods for controlling this vector insect were also examined. The following results were obtained. Emergence of the adults of, Monochamus alternatus, began on 13th June and continued to 30th July. The effective cumulative temperature for emergence to start and that when half of the total adults had emerged were 350 day･degrees and 620 day･degrees, respectively. More adult feeding marks were obtained on the 2- to 4-year old branches than any other branches. In general, the more feeding wounds the pine tree had, the earlier the tree withered. More bore holes were made by the sawyer larvae on the trunks of the pine trees that withered early. The ratio of the number of full-grown larvae to the number of bore holes, and the ratio of number of adults emerged to the number of bore holes were ca. 50% and ca. 25%, respectively. The insecticide treatment in autumn was the most effective of the attempts to kill the pine sawyer in infested pine logs, especially for the log previously split into several timbers. Splitting the infested logs without application of any insecticides was as effective for exterminating pine sawyers from infested log as the insecticide treatment without splitting. Thus, splitting of infested logs may be helpful in controlling this noxious insect in places where insecticide treatment is difficult to use.