Can habitat partitioning of thrips natural enemies reduce intraguild predation in greenhouses?

Although augmentative releases of natural enemies have been the traditional biological control tactic for greenhouse pest management, researchers and greenhouse managers have become increasingly interested in a concept termed ‘open rearing.’ Open rearing systems combine augmentative releases with conservational biocontrol by providing supplemental resources such as food and habitat to maintain natural enemy populations prior to pest invasions thus preventing pest outbreaks. However, maintaining natural enemies poses the potential for intraguild predation. Amblyseius cucumeris (Mesostigmata: Phytoseiidae) breeder piles are a form of open rearing used to manage thrips (Frankliniella occidentalis) in greenhouses. Breeder piles are placed on soil surfaces where these mites do not normally occur and exposes them to organisms with which they do not normally interact. Ongoing research shows that the presence of soil-dwelling fungus gnat and thrips predators, Atheta coriaria (Staphylinidae), drastically reduces A. cucumeris densities in breeder piles. Therefore, prevention of A. coriaria invasion is essential for worthwhile A. cucumeris open rearing. Partitioning A. cucumeris and A. coriaria habitats by using hanging sachets, an alternative approach to open rearing, is investigated.