Host specificity of Cotesia rubecula and Cotesia plutellae, parasitoids of white butterfly and diamondback moth

Abstract

Cotesia rubecula and Cotesia plutellae were assessed as potential biological control agents for white butterfly (Pieris rapae) and diamondback moth (Plutella xylostella), respectively, in New Zealand. Some literature records indicated a wider host range for C. plutellae compared with C. rubecula. The specificity of these parasitoids was evaluated by rearing collections of Lepidoptera from natural parasitoid habitats overseas, and by laboratory testing of their host preferences for related Lepidoptera and species from brassica habitats. C. rubecula showed strong preferences for white butterfly and developed in no other species. This parasitoid has now been released and its effectiveness and specificity are being confirmed in the field. Whereas C, plutellae demonstrated preferences for diamondback moth in oviposition rate and suitability for development, it was capable of developing in several other Lepidoptera in the laboratory. Current laboratory tests require very careful interpretation for predicting the field host range of species such as C. plutellae.