My goal was to identify and manage factors influencing open rearing of the thrips predatory mites Neoseiulus cucumeris Oudemans (Phytoseiidae) to improve biological control in greenhouses. I conducted a microcosm study in a greenhouse at Michigan State University to identify the potential for and effects of intraguild interactions among predators. Atheta coriaria (Kraatz) (Coleoptera) and Stratiolaelaps miles (Berlese) (Laelapidae), two predators commonly released to manage pests in greenhouses, were found to be intraguild predators that demonstrated negative effects on N. cucumeris populations when N. cucumeris were released in breeder pile open rearing systems placed on the growing media surface. I then tested an alternative release tactic --sachets in the plant canopy-- for mitigating these unfavorable interactions in two trials at a commercial greenhouse in Michigan. The use of N. cucumeris sachets were found to reduce the effects of intraguild predation by A. coriaria. Neoseiulus cucumeris densities produced by different open rearing systems and how long these predators were conserved in the systems were determined in two repeated greenhouse trials. Neoseiulus cucumeris sachets were found to contain more mites over time compared with breeder pile open rearing systems. Furthermore, I showed that N. cucumeris disperse quicker from breeder piles than sachets and that sachets conserve N. cucumeris longer than breeder piles. I consolidated this information into an extension bulletin for distribution to greenhouse operators.
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