外国産マツ属の虫害に関する研究 : 第6報 マツノマダラカミキリ成虫の後食について

Abstract

マツノマダラカミキリ成虫の後食によって伝播されたマツノザイセンチュウに起因するクロマツ, アカマツの集団枯損は, 西日本各地のマツ林に大きな被害をあたえている。本報告は, マツノザイセンチュウを伝播する重要な役割をになっているマツノマダラカミキリ成虫のマツ属に対する後食の可能性を1977年, 1978年に調査した結果をとりまとめたものである。飼育ビン (内径17cm, 高23cm) および網室 (底辺90×180cm, 高さ185cm) に, マツノマダラカミキリとともに入れられた29種のマツ属枝条は, すべてが後食され, 後食されなかったものは1例もみられなかった (表-1)。網室に, 11鉢に植られた11種のマツ属を並べ, 羽化2 - 3日後のマツノマダラカミキリ7匹の3 - 9日間の行動および後食状況を1977年に16組, 1978年に17組調査した結果, 供試した13種のマツ属は, いずれの種も後食され, 1度も後食されなかった種はなかった (表-2, 図-2)。網室内でのマツノマダラカミキリ成虫の行動はさまざまで, 190時間も同一樹体で後食を続けた個体もあれば, 数時間で樹体 (樹種) を移動したものもあり, 24時間以内に移動する場合が多かった (図-3)。移動は夜間に行なわれることが多く, マツノマダラカミキリ成虫は, 夜行性であると思われる。マツノマダラカミキリ成虫の後食痕面積の1コあたりの平均は, テーダマツ (P. taeda) 実験林で, 1977年は105mm_2, 1978年は112mm_2, スラッシュマツ (P. elliottii) 実験林で, それぞれ112mm_2, 114mm_2で, 平均後食痕面積は110 - 120mm_2と推定される。白浜試験地の見本樹として植えられている7種類のメキシコ産マツ属にも, マツノマダラカミキリの後食痕がみられ (表-5), P. taeda, P. elliottiiの実験林においても多くの後食痕が確認された (表-6)。さらに, 野外において, マツノマダラカミキリの後食 - マツノザイセンチュウの繁殖により枯死したP. elliottii (2本), P. taeda (3本), P. massoniana, P. thunbergii (♀)×P. massoniana (♂) のF_1, P. radiata, P. pinasterの9本を確認した。本調査の結果, マツノマダラカミキリの成虫はマツ属であれば, どの種でも後食することが明らかになった。

It is well-known that the severe damages to Japanese black pine (P. thunbergii) and red pine (P. densiflora) in pine stands throughout western Japan have been attributed to the attack of Japanese pine sawyer (Monochamus alternatus) and pine wood nematode (Bursaphelenchus lignicolus). Feeding of Monochamus alternatus in adult stage upon foreign pine species had been observed in glass bottle (17 cm in diameter and 23 cm height), net cage (90×180×185 cm) and field for two years, from 1977 to 1978 at the three Experimental Stations of Kyoto University Forest, Shirahama (Wakayama prefecture), Kamigamo (Kyoto prefecture) and Tokuyama (Yamaguchi prefecture). The results obtained from these investigations were as follows: 1. Twenty-nine pine species (including one variety) were infested with the adult of Japanese pine sawyer and its feeding wound had been observed on each shoot of these pines in bottles and cages (Table 1). 2. In cage, one adult stayed on the same tree for one hundred ninety hours, the other locomoted in a few hours from tree to another tree. Most of locomotion was practiced within twenty-four hours (Fig. 2 and 3). 3. Some adults locomoted from pine to pine during the daytime, but most of adults were mobile during the period from 5 p.m. to 9 a.m. of next day. Therefore, it seems that the active type of the adult is nocturnal. 4. The area of feeding mark in loblolly pine stand was 105 mm2 in 1977 and 112 mm2 in 1978 on an average, and in slash pine stands its mean area was 112 mm2 in 1977 and 114 mm2 in 1978. 5. At Shirahama, the adult feeding mark were observed on stems and shoots of seven pines which were native to Mexico (Table 5). And also, in healthy loblolly and slash pine stands, many feeding wound of sawyer adult were observed on its healthy shoots and twigs (Table 6). 6. Further, nine pine trees among six species had been withering in each stand by the attack of Japanese sawyer adult which carried pine wood nematodes, two slash pines and three loblolly pines at Shirahama, a tree of P. massoniana and F1 hybrid of P. thunb. (♀) P. masso. (♂) at Tokuyama and a tree of P. radiata and P. pinaster at Kamigamo. Pine wood nematodes were recovered from stems and branches of these withering pines. 7. Feeding preference of pine sawyer adult to pine species is not observed, therefore, it seems that all pine species may be infested with the adult of Japanese pine sawyer when the occasion comes.