外国産マツ属の虫害に関する研究 : 第2報 マツカレハ幼虫の摂食について

Abstract

京都大学農学部附属演習林上賀茂育種試験地で, 外国産マツ属に対するマツカレハの摂食を調査し, 1963年7月までに判明したのはつぎのことがらである｡ 1. 当試験地構内の植栽地で, マツカレハの幼虫が, 外国産のマツ24種を食害しているのを確認した｡ その他, 外国産マツ8種は現在のところマツカレハの幼虫が食害しているのを観察できなかった｡ マツカレハの幼虫が食害していた24種のうち P.ayacahuite, P. banksiana, P. radiata の3種は各1例にすぎなかったが, 非常に激しく食害され, 7月中旬にはほとんど全部の針葉をうしなっていた｡ 2. 外国産マツ26種について, 野外でサランネットを用いてマツカレハ幼虫を強制的に寄生させた結果, 2, 3の幼虫は死亡したが, 1樹種に寄生させた2頭ともに死亡したものはなく, 供試虫の大部分は蛹化, 羽化した｡ 3. 外国産マツ18種の針葉を餌として, 飼育ビンでマツカレハ幼虫を個体飼育した結果, いずれの幼虫も蛹化した｡ 4. マツカレハの幼虫の個体飼育の結果より, 摂食量と脱糞量との関係を求めると, アカマツの針葉を餌とした場合と非常によく似た関係が得られた｡ すなわち, 摂食量と脱糞量とは両対数グラフ上で直線関係が得られるが, アカマツの場合と比べてそれらは全く同じではなく, それはやや平行的な差がみられた｡ またこの関係は, 外国産マツ属樹種間による差はほとんどみられないようである｡ 5. 現在までの野外での調査と強制摂食および個体飼育の結果から, マツカレハの幼虫が外国産マツ28種を摂食することを確認した｡ さらにこれから推測して, マツ属であればいずれの樹種でもマツカレハの幼虫により被害をうけることが推察される｡

It is well-known that the pine caterpillar (Dendrolimus spectabilis Butler) is the most injurious among the leaf-eating insects of the red pine (Pinus densiflora S. et Z.) and the black pine (P. thunbergii Parl.) and frequently gives the greatest damage to these forests in Japan. Besides, it seems that this caterpillar gives the damage to many pine-species imported in Japan. On the feeding of this caterpillar to these foreign pine-species, the reports investigated in detail could scarcely be found as far as we could review. In this report, the authors deal with some investigations on the feeding of the pine-caterpillar to many foreign pine-species from 1960 to 1963, which are planting in the Kamigamo Breeding Experimental Forest Station of Kyoto University. The results obtained from these investigations were as follows: 1. We found that twenty-four species among the foreign pine-species were infested with the pine caterpillar but the other eight species were not in these planting. In case of three species, P. ayacahuite, P. banksiana, P. radiata, out of these twenty-four species, only a tree of each species was infested very heavily, and almost all needle-leaves of its crown had been defoliated in the middle of July in 1963. These twenty-four and eight foreign pine-species were as follows: the former: P. australis, P. ayacahuite, P. ayacahuite var. brachyptera, P. banksiana, P. echinata, P. elliottii, P. excelsa, P. laricio var. calabrica, P. laricio var. corsicana, P. luchuensis, P. massoniana, P. muricata, P. nigra, P. pinaster, P. pinea, P. ponderosa, P. pungens, P. radiata, P. rigida, P. strobus, P. sylvestris, P. sylvestris var. Rigensis, P. taeda, P. virginiana the latter: P. armandi, P. halepensis, P. jeffreyi, P. laricio var. pallasiana, P. nigra var. austriaca, P. patula, P. peuce, P. torreyana 2. After a part of branches of each twenty-six foreign pine-species was covered with the saran-net, the two larvae of the pine caterpillar at the sixth instar were put into the net at each foreign pine in May of 1961. Some larvae were dead by an accident, however one larva at the very least of the two at each foreign pine pupated early and middle in July and grew wings from July to August. These twenty-six foreign pine-species were as follows: P. armandi, P. australis, P. ayacahuite var. brachyptera, P. banksiana, P. echinata, P. elliottii, P. excelsa, P. halepensis, P. laricio var. calabrica, P. laricio var. corsicana, P. luchuensis, P. massoniana, P. muricata, P. nigra, P. patula, P. peuce, P. pinaster, P. pinea, P. ponderosa, P. pungens, P. rigida, P. strobus, P. sylvestris, P. sylvestris var. Rigensis, P. taeda, P. virginiana 3. As the result of the individual breeding of pine caterpillar fed on the needle-leaves of eighteen foreign pine-species at the last ten days of May in 1961, any larva pupated in July. These eighteen foreign pine-species were as follows: P. banksiana, P. echinata, P. elliottii, P. massoniana, P. nigra, P. pinaster, P. pinea, P. pungens, P. sylvestris, P. virginiana, P. patula, P. radiata, P. rigida, P. taeda, P. ayacahuite, P. excelsa, P. peuce, P. strobus 4. When the caterpillar ingested the needle-leaves of the foreign pine, the correlations between the feeding quantity and the amount of the frass were shown with the straight line in the logarithms as it was the red pine. These were not the same entirely in comparison with the red pine, but there was not the difference of these correlations in the foreign pine-species. 5. As the results of the observation of the feeding in planting, the breeding with the aid of the net in the same place and the individual breeding, we could find that the pine caterpillar ingested twenty-eight foreign pine-species in Kamigamo. From these investigations, it seems to be possible that every species of the pine-genus in Japan is infested with the pine caterpillar.