ABSTRACT

Biological control in the open field often involves simultaneous infestations of different pest species. In brassica crops, aphids and diamondback moth are major pest species worldwide. The aphidophagous Coccinellinae Eriopis connexa (Germar) is a common predator in crop ecosystems including brassicas. We hypothesised that the performance of E. connexa would be improved if it were fed a mixed diet of prey available in the brassica ecosystem compared with the standard rearing prey; eggs of Anagasta kuehniella (Zeller). We evaluated diamondback moth, Plutella xylostella (L.) larvae, the brassica aphid, Lipaphis pseudobrassicae (Davis) when provided as single species, as mixtures of two species, or as all three species alternated over time. Developmental time and survival of E. connexa larvae fed diets of mixed prey and alternated available prey were superior to individuals that fed only P. xylostella larvae. Only 33% of E. connexa larvae that fed on P. xylostella alone survived and their development was delayed by 6 days. However, mean daily predation of P. xylostella larvae as single, mixed or alternated prey was 9.1 ± 0.2, 3.1 ± 0.1 and 9.4 ± 0.5 individuals, respectively, showing that this species was consumed even in the presence of preferred prey. Adult female E. connexa that consumed only P. xylostella did not lay eggs indicating that this prey could sustain the development and maintenance of E. connexa, but they are not essential prey. Predation of P. xylostella did not enhance or negatively affect E. connexa performance.

摘要

露地的生物控制通常涉及不同害虫物种的同时侵染。在芸苔属作物中，蚜虫和小菜蛾是世界范围内的主要害虫物种。蚜虫 Coccinellinae Eriopis connexa (Germar) 是作物生态系统中常见的捕食者，包括芸苔属植物。我们假设，与标准饲养的猎物相比，如果用芸苔属生态系统中可用的猎物的混合饮食喂养E. connexa的性能会有所提高；Anagasta kuehniella (Zeller) 的鸡蛋。我们评估了小菜蛾、Plutella xylostella (L.) 幼虫、芸苔蚜虫、Lipaphis pseudobrassicae(Davis) 当作为单一物种、两种物种的混合物或所有三种物种随时间交替提供时。喂食混合猎物和交替可用猎物饮食的E. connexa幼虫的发育时间和存活率优于只喂食小菜蛾幼虫的个体。仅以小菜蛾为食的E. connexa幼虫只有 33%存活，并且它们的发育延迟了 6 天。然而，平均每天捕食P。xylostella 幼虫作为单一、混合或交替猎物分别为 9.1 ± 0.2、3.1 ± 0.1 和 9.4 ± 0.5 个体，表明即使在首选猎物存在的情况下，该物种也会被消耗。成年雌性E. connexa只食用小菜蛾不产卵表明这种猎物可以维持E. connexa的发育和维持，但它们不是必需的猎物。P. xylostella 的捕食不会增强或负面影响E. connexa 的性能。