Biological control of spider mites in strawberries and tomatoes: Occurrence and efficacy of resident and released populations of Phytoseiulus persimilis in North and South Carolina

The twospotted spider mite (TSSM, Tetranychus urticae Koch) is a key pest in many fruit and vegetable agroecosystems. Augmentative or inoculative biological control of TSSM is a commonplace and effective management strategy in greenhouses worldwide, but in field-grown crops biocontrol of TSSM is less developed and understood. Over several years, we have conducted a number of studies on commercial farms and in small-plot experiments to investigate the use of the predatory mite, Phytoseiulus persimilis, for biological control of TSSM in staked tomatoes and strawberries. These studies have determined the environmental and operational factors contributing to successful biological control of TSSM, including release rates and timing, predator dispersal, extent of management beyond release points, and predator compatibility with various pesticides. Additionally, natural populations of P. persimilis have established and overwinter in multiple regions in SC and NC. Sampling conducted on commercial farms has investigated the distribution and efficacy of these populations for managing TSSM, in addition to determining the factors facilitating their conservation and enhancement. This research has demonstrated the utility and limitations of P. persimilis in strawberry and staked tomato fields, which is a promising option for growers to manage TSSM in these and other crops in the southeast United States.