Dispersal of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) on potted greenhouse chrysanthemum

Dispersal of natural enemies through a crop is a key component of biological control. The release strategy should optimize the number of predators that are released, the release frequency and number of release sites throughout a crop with regards to the distance that natural enemies can disperse from their release point. In this study, dispersal rate and behaviour of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae)was investigated in potted greenhouse chrysanthemums in the presence or absence of prey (Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Results demonstrate that A. swirskii did not disperse far from the release site. Presence of prey did not influence dispersal, but had an effect on predator survival in one experiment. Only a quarter of the A. swirskii eventually attempted to disperse by going down to the ground. The presence of inter-plant contact greatly improved movement of A. swirskii between plants. It is concluded that good coverage with predators of the crop is needed when using A. swirskii in a biological control program. Having a continuous crop canopy will promote dispersal.