ｸﾜｼﾛｶｲｶﾞﾗﾑｼの天敵寄生蜂に対する農薬の影響

　茶樹の重要害虫となっているクワシロカイガラムシPseudaulacaspis pentagona（Targioni）の主要天敵であるナナセツトビコバチThomsonisca typica MERCETとチビトビコバチArrhenophagus chionaspidis GIRAULTに及ぼす農薬の影響を室内試験で解析した。ナナセツトビコバチ成虫に対する農薬の殺虫作用を15剤について切り枝接触法で調査し，チビトビコバチ成虫に対する農薬の殺虫作用を13剤について雌雄別に調査した。さらに，切り枝接触法で24時間にわたって農薬に暴露したチビトビコバチ成虫の次世代増殖数を調査した。

　２種の天敵寄生蜂成虫に対して殺虫作用の低い農薬は，メトキシフェノジドフロアブル，エマメクチン安息香酸塩乳剤であった。チビトビコバチの次世代増殖数への影響は，スピノサドフロアブルでは認められず，メトキシフェノジドフロアブルでは小さかった。その他の剤は次世代増殖数に及ぼす影響が大きく，特に，クロチアニジン水溶剤，アセタミプリド水溶剤，エマメクチン安息香酸塩乳剤では次世代成虫は認められなかった。また，各農薬の成虫生存率と次世代増殖数には相関がみられなかった。以上のことから，土着天敵に影響の少ない農薬を選定する場合には，成虫に対する殺虫作用だけではなく，次世代増殖数に及ぼす影響についても配慮することが必要である。

　Effects of Pesticides on Thomsonisca typica MERCET and Arrhenophagus chionaspidis GIRAULT, Parasitoids of Pseudaulacaspis pentagona (Targioni). YOSHIOKA Tetsuya and Mitsuyoshi TAKEDA (Fukuoka Agricultural Research Center, Chikushino, Fukuoka 818-8549, Japan) Bull. Fukuoka Agric. Res. Cent. 25; 145-149 (2006)

　Effects of pesticides on Thomsonisca typica MERCET and Arrhenophagus chionaspidis GIRAULT, the main natural enemies of Pseudaulacaspis pentagona (Targioni), were evaluated under laboratory conditions. The pesticidal activities of 15 pesticides on the adult females of T. typica were investigated with a dipping method using tea branches for contact toxicity, and those of 13 pesticides on the adults of A. chionaspidis were also investigated in each sex. In addition, the numbers of A. chionaspidis, developed to the pupal or adult stage and reared on pumpkin fruits, were investigated when exposed to pesticides during their parental stages by way of dipping tea branches in pesticides for 24 hours.

　Methoxyfenozide and emamectin benzoate were found to be slightly harmful on the two species of parasitoids. Spinosad had no effect on the number of progeny of A. chionaspidis, while methoxyfenozide had small effect. Stronger harmful effects on reproduction were observed with the application of other pesticides; and, it was found that none of the progeny reached the pupal or adult stage when clotianidin, acetamiprid, and emamectin benzoate were applied. And, no significant correlation was found between the survival rate of the adults and the number of progeny with the application of these pesticides. Thus, it is necessary to examine not only the pesticidal activity on the adults but also the reproductive potential of the parasitoids when choosing pesticides with small effects on indigenous natural enemies.