白蛾周氏啮小蜂转主寄主的研究

Studies on Alternate Hosts of the Parasiotid Chouioia cunea (Hymenoptera: Eulophidae)

白蛾周氏啮小蜂是美国白蛾的优势寄生性天敌。为了了解其在释放利用后能否保持高的种群数量 ,达到对美国白蛾的持续控制效果 ,研究了这种小蜂在林间的转主寄主。通过调查 ,明确了白蛾周氏啮小蜂在林间的转主寄主种类 ,并研究了这些寄主的年生活史和生物学特性 ,以及白蛾周氏啮小蜂在这些寄主中的寄生率和出蜂量、雌雄性比等。结果表明 ,白蛾周氏啮小蜂的寄主有 7种 :美国白蛾 ,大袋蛾 ,柳毒蛾 ,榆毒蛾 ,国槐尺蛾 ,杨扇舟蛾和桃剑纹夜蛾。白蛾周氏啮小蜂年发生 7代 ,而美国白蛾年发生 2代 (部分年份可发生 3代 ) ,小蜂除寄生这 2代(或 3代 )美国白蛾蛹外 ,其余各代在这些转主寄主蛹中寄生。这些转主寄主的蛹期和美国白蛾的蛹期在 1a的生长发育期中相互衔接 ,小蜂可转移寄生在这些寄主上 ,从而能够保持较高的种群数量 ,达到对美国白蛾的持续控制。对各地白蛾周氏啮小蜂在柳毒蛾和美国白蛾上的寄生情况比较分析 ,发现该小蜂在不同地点的寄生情况差异不显著 ,说明这种小蜂的分布比较广泛 ,种群数量比较稳定。研究还表明 ,绿化树木的多样性可以增加转主寄主的种类和数量 ,从而能够使小蜂保持较高的种群数量 。

The chalcidoid wasp Chouioia cunea (Hymenoptera: Chalcidoidea, Eulophidae) is a predominant parasitoid in pupa of the important introduced defoliator Fall Webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae) in China. For understanding the potential of sustainable management of the pest in biological control by mass rearing and releasing the parasitoid, its alternate hosts were investigated in forests. Through two_year investigations, the species of alternate hosts and their life history, as well as biology were figured out. And the parasitism rate, offspring number, and sex ratio of the parasitoid on those hosts were also surveyed. Results showed that there mainly were six other defoliator species (Lepidoptera) as its alternate hosts besides Fall Webworm, i.e. Clania variegeta (Psychidae), Stilpnotia salicis, Ivela ochropoda (Lymantriidae), Semiothisa cinerearia (Geometridae), Clostera anachoreta (Notodontidae), Acronycta increta (Noctuidae). The parasitoid C. cunea developed seven generations in a year compared with only two generations (occasionally three generations) of Fall Webworm. Besides the two (and/or three) pupal stages of Fall Webworm, the wasp could parasitize those alternate hosts in its other generations because the pupal stages of those hosts were existed and just filled the gaps between the pupal stages of Fall Webworm. Thus, it could keep higher population to control the Fall Webworm after it was released. Results of the investigation showed that the parasitoid distributed widely and the population were relatively stable. It was also indicated that certain population of C. anachoreta and A. increta in forest stands is important for the parasitoid to increasing the population. Furthermore, it could be concluded that the tree_species diversity was a main factor for the parasitoid to keep Fall Webworm under control sustainablly.