Performance of the aphidophagous coccinellid Eriopis connexa fed on single species and mixed-species prey

Abstract

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.