Supplementing food and shelter to predatory mites to improve thrips control in strawberry protected crop

Abstract: The western flower thrips Frankliniella occidentalis is one of the main pest on
strawberry production. The predatory mites Amblyseius swirskii and Neoseiulus cucumeris and the predatory bug Orius laevigatus are commonly used by growers to control thrips in
strawberry greenhouse production. The main goal of this study was to test whether providing
external food source and shelter could improve their establishment into the crop, and
consequently allow a better control of the pest. A layer of 2-3 cm of buckwheat husks was
deposited on the substrate used for strawberry growth, as shelter for predatory mites. Two
sources of food were tested: pollen of Typha angustifolia and prey mites Thyreophagus
entomophagus. Then, the companion plant Lobularia maritima (sweet alyssum) was used as a shelter and food source for O. laevigatus. In the presence of buckwheat husks and pollen,
population of predatory mites were significantly higher and thrips significantly lower,
compared to the control. Indeed, the population of predatory mites increased by 35 %, and
consequently thrips reduced by 20 %. The population of O. laevigatus did not establish on
strawberry in this trial. However, we observed a significant increase of the predatory mites on
strawberry plants when sweet alyssum was present as a companion plant compared to
strawberry plants without sweet alyssum. This observation suggested that sweet alyssum could act as an effective companion plant for predatory mites providing food and shelter.