Impact of low release rates of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera : Reduviidae) on Helicoverpa spp. (Lepidoptera : Noctuidae) and Creontiades spp. (Hemiptera : Miridae) in cotton

摘要

A challenge with the inundative release of beneficial insects in pest management programs is to achieve a viable balance between predator release rates and biological control efficacy. This paper examines postrelease survival and biological control efficacy of the assassin bug, Pristhesancus plagipennis (Walker) released in cotton at rates of 1.0, 0.75, 0.5 and 0.25 nymphs per metre crop row. These releases resulted in >72% survival of nymphs with respective field populations of 0.75, 0.54, 0.41 and 0.25 nymphs m(-1) 4 weeks postrelease. Each of the P. plagipennis nymph release treatments gave significant reductions in Helicoverpa spp. larval densities, whilst only the higher nymph release rates of 1.0 and 0.75 m(-1) decreased densities of mirids, Creontiades spp. The data suggest that release rates of P. plagipennis at or below 1.0 nymph m(-1) aid postrelease survival and provide significant reductions in numbers of some cotton pest insects.