The effect of sweet alyssum planting arrangement on twospotted spider mite management with the predatory mite Neoseiulus californicus in organic strawberries in Florida

The twospotted spider mite, Tetranychus urticae Koch, is a major pest of strawberries and many other crops throughout the world. Feeding injury to leaves inhibits photosynthesis, which can lead to yield loss when mite populations are high. Spider mites can quickly become resistant to miticides, so other control tactics must be employed to preserve the efficacy of effective miticides. This is even more important for organic growers who have fewer miticide options to begin with. One such tactic is the release of predatory mites like Neoseiulus claifornicus (McGregor), which prefer spider mite prey but can subsist on other small arthropods and pollen when mites are unavailable. Flowering plants, like sweet alyssum (SA), Lobularia maritima (L.), used as companion plants can provide a refuge for predators and pollen for an alternative food source. The purpose of this study was to determine the best planting arrangement for SA in strawberries. Plots consisted of two 3 m beds. An untreated control and treatment with releases of N. californicus with no SA planted were compared with three SA planting arrangements: 1) SA planted as clusters in the middle and at either end of each bed, 2) SA planted down the middle of each bed, and 3) SA planted between the two beds. Spider mite numbers were low throughout the season due to the presence of six-spotted thrips, Scolothrips sexmaculatus (Pergande), throughout the field. There were fewer spider mite eggs in the down the middle treatment compared with the between the beds treatment.