Effect of sweet alyssum on efficacy and sustainability of Neoseiulus californicus (Acari: Phytoseiidae) for biological control of spider mites in multiple cultivars of organic strawberries

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is one of the major pests of strawberry in the United States, causing losses of photosynthetic efficiency of up to 30% in strawberries. The predatory mite, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is one of the primary biological control agents used against T. urticae in strawberries in Florida. We hypothesized that intercropping sweet alyssum (Lobularia maritima (L.)) would provide pollen as an alternative food source for N. californicus, allowing populations to survive longer when their preferred prey, spider mites, is not available. To test this hypothesis, three treatments including sweet alyssum in combination with N. californicus mites, N. californicus mites (only), and a miticide regimen were evaluated in in a field study. We found that N. californicus mites consistently controlled the spider mite population when populations were high compared to a miticide regimen (control). Furthermore, there was no evidence that the presence of sweet alyssum affected the efficacy or sustainability of N. californicus. The implications of these results are discussed for organic growers who favor banker planting.