Drone-released versus hand-released predatory mites for biological control of strawberry pests in Florida

Soft bodied arthropod pests of strawberry such as thrips and mites are difficult to manage. Resistance to insecticides is a long-standing issue. New invasive species such as the chilli thrips, Scirtothrips dorsalis Hood, make the matters worse. In the face of such challenges, biological control techniques provide a feasible alternative. Efficacy of Type I predator, Phytoseiulus persimilis (Athias-Henriot) in controlling twospotted spider mites, Tetranychus urticae Koch is well documented. Type III generalist predator, Amblyseius swirskii (Athias-Henriot) is an effective biocontrol agent of thrips, S. dorsalis. Growers conduct hand-release of P. persimilis, currently, in Florida, but this needs labor. Drones provide an alternative to perform augmentative biocontrol. However, the best-suited strategy to release these predators in open-field strawberry is not well explored.
Therefore, the objective of this study is: determining establishment of P. persimilis and A. swirskii released by drone and hand when compared to non-treated control plots of strawberry. A 16 Acre organic strawberry field was used to conduct this experiment, where the field received drone released P. persimilis and A. swirskii in separate plots and non-treated control plots were used to compare predator establishment. Field was sampled 7 and 14 days after treatment (DAT), where a presence/absence record was made per plant sampled. A total of 72 plants were randomly sampled per predator species.

Results indicate that A. swirskii established on 44% of plants sampled versus only 6% in case of P. persimilis. Additionally, control plots remained devoid of predators even 14 DAT.