Studies on the Insect Damage upon the exotic Pine-species introduced in Japan : (No. 8) Further Report on Japanese Pine Needle Gall Midge, Thecodiplosis japonensis Uchida et Inouye

本報告には, マツバノタマバエのマツ属に対する加害を調査した前報を確認し, 新しい加害種を調査し, さらに被害針葉の長さ, 虫癭の大きさ, 虫癭内幼虫数について調査した結果がまとめられている。1. マツバノタマバエの虫癭が認められたマツ属16種は, P. radiataを除き, Critchfield & Littleがマツ属を分類したSylvestres亜節に含まれ, マツバノタマバエのマツ属への寄生とマツ属の感受性が, マツ属の分類と一致していることが判明した。これはShawや石井の分類においても同様である。2. P. thunbergiiを雌性親とした5F_1雑種 - 雄性親はP. massoniana, P. tabulaeformis, P. luchuensis, P. taiwanensis, P. khasya - はいずれもマツバノタマバエの加害をうけ, とくに, P. thunbergii×P. massoniana (F_1), P. thunbergii×P. tabulaeformis (F_1), P. thunbergii×P. khasya (F_1) では, 両親より被害が激しかった。3. マツバノタマバエの虫癭は, 2針葉の各種のみならず, P. yunnanensis, P. khasya, P. thunbergii×P. khasya (F_1), P. radiataの3針葉にも形成されていた。4. マツバノタマバエの虫癭が形成された針葉は, いずれも無被害針葉より短く, 平均して正常葉の35 - 45％の長さのものが多かった。正常葉の短いP. sylvestrisやP. mugoでは, 被害針葉も約70％の長さで, 正常葉と大きな差はなかったが, とくに針葉の長いP. luchuensisやP. yunnanensisでは, その30％も伸長していなかった。5. 虫癭内の幼虫は, P. thunbergii×P. khasya (F_1) の2針葉に作られた虫癭で, 最大25頭が数えられたが, 種ごとに平均すると, P. sylvestrisの3. 0頭が最少で, P. thunbergii×P. khasya (F_1) の2針葉の9. 8頭が最多で, 3 - 5頭が多かった。6. 虫癭の大きさには, 種によりいくらか差がみられ, 虫癭が大きいほど, 幼虫が多く生息している傾向がみられた。The attacks of Japanese pine neddle gall midge, Thecodiplosis japonensis Ucliida et Inouye, upon the exotic pines had been observed at the two Experimental Stations of Kyoto University, Kamigamo in Kyoto prefecture and Shirahama in Wakayama prefecture in 1985 and 1086. The results obtained from this investigations were as follows: 1. Sixteen pine species and five F1 hybrids were infested with the larvae of pine needle gall midge. The development of galls were observed mostly in the bottom of needle covered with the leaf sheath, only a few in the middle part of the needle. 2. All gall had been formed in both of the binate and the ternate needles in a fasicle of susceptible pines to this gall midge. 3. Three F1 hybrids of P. thunbergii × P. massoniana F1, P. thunbergii × P. tabulaeformis F1 and P. thunbergii × P. khasya F1 had been infested severely with this pest as compared with these parents. 4. Fifteen pines except P. radiata infested with this gall midge have been classified into subsection "Sylvestres" by Critchfield & Little. 5. The length of gall formed needle was shorter than that of the normal needle in all damaged pines. That is, its length showed from 30% to 70% as compared with normal needle length and there were observed many gall formed needle in 35~45% to the normal. 6. The number of larvae was in maximum 25 in a gall of the binate needle of P. thunbergii × P. khasya F1 hybrid. In average, the larvae per a gall were 3.5~4.5 of many pines generally. 7. It seemed that the number of larvae became more numerous in proportion to the volume of gall