Evaluating biocontrol agents against emerging Scirtothrips species in strawberry

Abstract: Species of the sub-tropical genus Scirtothrips (Thysanoptera: Thripidae) are
emerging as serious pests in several crops. Scirtothrips inermis is ubiquitous in the Canary
Islands and has been reported also in mainland Europe infesting both orchards and horticultural crops. Another invasive species S. dorsalis has repeatedly been intercepted in mainland Europe and the Canary Islands. Both Scirtothrips species are polyphagous, and in recent years have emerged as pests of strawberry in the Canary Islands and other parts of the world. In this study, we first evaluated the predation and oviposition rate of the commercially available predatory mites Amblyseius swirskii, Amblydromalus limonicus, Transeius montdorensis and Neoseiulus cucumeris (Acari: Phytoseiidae) on larval stages of both Scirtothrips species in the laboratory. All predatory mites equally accepted both thrips species as prey and showed stable oviposition rates on these diets. A. swirskii and A. limonicus were the most voracious predators. We further tested their biological control potential in a greenhouse trial, where Orius laevigatus (Hemiptera: Anthocoridae) and the endemic to the Canary Islands Orius limbatus were also included. Predators were released preventively and supported with Artemia cysts prior to the introduction of S. inermis. Both Orius predators achieved good control of the pest, with O. limbatus developing higher numbers than O. laevigatus. Regarding phytoseiids, A. swirskii and A. limonicus both controlled the pest and built higher populations than T. montdorensis and N. cucumeris. Our results show that a preventive strategy on the strawberry crop can be effective in suppressing S. inermis.