Establishment of fundamental theory for classical biological control - a case study on biological control of arrowhead scale -

以引进的两种寄生蜂黄葡萄球菌（Aphytis yanonensis）和黄球虫（Coccobius fulvus）为研究对象，建立了经典生物防治的基本理论。首先，研究了两种寄生蜂的生物学特性，以评价其作为天敌的有效性。结果表明，这两种寄生蜂是互补的天敌，两种寄生蜂的联合防治效果较好。第二，对一种拟寄生蜂引入后果园内褐杨种群动态的研究结果表明，任一种的单种引入都会导致褐杨种群水平下降。然而，在只引进褐杨的果园中，引入黄僵菌后，褐僵菌的密度再次下降，这表明了多物种引进在经典生物防治中的优势。通过对引进寄生蜂的果园中杨柳木种群动态的分析，证明了多种引进的优越性。另一方面，对这两种寄生蜂对本地蚧虫寄生的现有资料分析表明，这两种寄生蜂的引入并没有太大的环境风险。最后，由于冬季温暖的原因，鸭见越冬代的年龄结构年际变化波动较大，种群动态不如日本大陆稳定。由此可见，在全球变暖的影响下，日本大陆柑桔园的冬季寒冷程度有所缓解，从而加剧了日本本土柑桔园的延青叶枯蝇种群波动。

Biological control of Unaspis yanonensis by using two introduced parasitoids, Aphytis yanonensis and Coccobius fulvus was examined as a case study for establishing basic theory of classical biological control. First, I investigated biological characteristics of the two parasitoids to evaluate their effectiveness as natural enemies. As the result, the two parasitoids were complementary as natural enemies of U. yanonensis, and it was indicated that combination of the two parasitoids resulted better results as biological control of the pest. Second, results of the study of population dynamics of U. yanonensis in orchards after the introduction of one of the parasitoids indicated that single species introduction of either species was resulted in the reduction of the population level of U. yanonensis. Howevere, density of U. yanonensis reduced again after the introduction of C. fulvus to the orchard where only A. yanonensis had been introduced This suggested the superiority of the multiple species introduction in classical biological control. The analysis of population dynamics of U. yanonensis in the orchard where the parasitoids were also introduced indicted the superiority of the multiple species introduction. On the other hand, analysis of the existing information on parasitism of the two parasitoids on indegenous scale insects suggested that there was not so serious environmental risk on the introduction of the two parasitoids. Finally, annual change in age structure of the overwintering generation of U. yanonensis fluctuated more in Amaimi than in mainland Japan because of the winter warmness and the population dynamics of U. yanonensis was not so stable as in mainland Japan. From this fact, it was suggested, the population fluctuation of U. yanonensis was intensified in citrus orchard in mainland Japan when the winter coldness was mitigated as the effect of global warmisation.