The present study aimed to explore some simple ways to optimize the mass rearing of Cotesia vestalis (Haliday) (Hymenoptera: Braconidae), one of the most important biocontrol agents of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). The effects of host and parasitoid initial densities on the quantity and quality of produced wasps were investigated. In particular, a factorial experiment was established using three different host densities (20, 50, and 100 P. xylostella larvae per cage) in presence of C. vestalis at three different densities (2, 5, and 7 females, with a 24-h exposure) in well-ventilated cages. There was a significant effect of wasp’s initial density on the percentage parasitism (measured based on the cocoon and emerged adult wasps); comparatively the greatest percentage parasitism was obtained with five wasps per cage. Initial host density had no significant effects on the percentage parasitism, sex ratio, and larval period, but it influenced the survival rate (measured based on the cocoon and adult emerged) and pupal period of produced wasps, and also percentage host mortality. The density of 20 host larvae was the best in this regard. These findings were discussed in the contexts of optimum mass rearing, life history, and potential of C. vestalis as a biological control agent.

中文翻译：

---

基于寄主和寄生虫密度的Cotesiavestalis（Hymenoptera：Braconidae）的大规模饲养优化

针对本研究，探索一些简单的方法来优化大规模饲养的绒茧蜂vestalis（茧蜂）（膜翅目：茧蜂科），小菜蛾的最重要的生物防治剂之一，小菜蛾（L.）（鳞翅目：菜蛾科）。研究了寄主和寄生虫的初始密度对所产黄蜂数量和质量的影响。特别是，在存在角质衣原体的情况下，使用三种不同的宿主密度（每笼20、50和100 P. xylostella幼虫）建立了析因实验。在通风良好的笼子中以三种不同的密度（2、5和7只雌性，暴露24小时）。黄蜂的初始密度对寄生率（根据茧和成年黄蜂的测量）有显着影响；相对而言，每笼五个黄蜂可获得最大的寄生率。初始寄主密度对寄生虫百分率，性别比和幼虫期没有显着影响，但会影响所产生的黄蜂的存活率（根据茧和成年成虫测量）和p期，以及寄主死亡率。在这方面，20个寄主幼虫的密度是最好的。这些发现是在最佳群体饲养，生活史以及猪毛衣原体作为生物防治剂的潜力的背景下进行讨论的。