Intraguild predation of Neoseiulus cucumeris by Stratiolaelaps miles and Atheta coriaria in greenhouse open rearing systems

We examined intraguild predation of Neoseiulus cucumeris Oudemans (Phytoseiidae) in breeder piles by the soil-dwelling predators, Stratiolaelaps miles (Berlese) (Laelapidae) and Atheta coriaria (Kraatz) (Staphylinidae) in a greenhouse microcosm study. Each microcosm contained a soybean plant (Glycine max (L.) Merrill) and a N. cucumeris breeder pile alone, a N. cucumeris breeder pile with either S. miles mites or A. coriaria, or a N. cucumeris breeder pile with both S. miles and A. coriaria. We measured numbers of N. cucumeris, S. miles, A. coriaria, and their shared prey: Tyrophagus putrescentiae (Shrank) (Acaridae) mold mites and incident thrips (Thripidae: Frankliniella occidentalis and Thrips sp.). Peak populations of N. cucumeris in breeder piles and soybean canopies lacking S. miles and/or A. coriaria predators were fourfold greater than when other predators were present. We observed more N. cucumeris mites in plant canopies in microcosms where other predators were absent. S. miles had a significant negative impact on A. coriaria and A. coriaria had numerical negative impacts on S. miles. There were fewer T. putrescentiae mold mites in microcosms containing A. coriaria (⩽1049.28 ± 301.72) compared with other treatments (⩾2428.16 ± 452.24) overall. We observed fivefold more incident thrips in microcosms containing all three predators compared with N. cucumeris breeder pile alone and N. cucumeris breeder pile with either of the other predators. Our results demonstrate that greenhouses seeking to biologically manage thrips should either utilize N. cucumeris alone or utilize alternative N. cucumeris release strategies - i.e. hanging sachets or repeated foliar applications.

Highlights► We investigated potential intraguild predation of Neoseiulus cucumeris. ► Atheta coriaria had negative impacts on N. cucumeris in breeder piles. ► Stratiolaelaps miles had negative impacts on N. cucumeris in breeder piles. ► Thrips densities were highest when all three predator species were present.