Biocontrol of spider mites on strawberry using predatory mites (Phytoseiidae) is a well-known system. However, control success is still highly unpredictable and new production practices, including growing under plastic tunnels, warrants further investigation into this classic tritrophic system. How commercially reared predators navigate novel hosts after release is unknown, and could explain variable control efficacy in the field. Here we present preliminary data on dispersal of phytoseiids reared from alternative hosts on novel bean and strawberry plants in lab, and on low tunnel strawberry in the field. Neoseiulus fallacis and Phytoseiulus persimilis were reared on bean and strawberry plants for > 10 generations. Single females from both colonies were released onto a bean or strawberry leaf disc bridged to a second leaf disc of the same plant. The location of the female (i.e., on release point or dispersed) was recorded every 15 minutes for 3 hours. Groups of 100 individuals of each species from both colonies were marked and released onto a commercial low tunnel strawberry field. Leaflets from the release point were collected at 2, 6, 24 and 48 hours post release and observed for retained phytoseiids. Both experiments suggest that rearing host plant affects phytoseiid dispersal on novel hosts, specifically that dispersal is higher when released on hosts experienced by the predator during rearing compared to unexperienced alternative hosts. These results are intended to explain variability in biocontrol success in the field, and to possibly inform commercial insectaries on rearing practices that produce more reliable biocontrol agents.
