Optimizing biological control of Tetranychus urticae with the predatory mite Phytoseiulus persimilis in staked tomato systems

The twospotted spider mite (TSSM, Tetranychus urticae Koch) is a key pest of tomatoes (Solanum lycopersicon L.) in North Carolina, and its management has relied principally on synthetic acaricides. Augmentative biological control of TSSM is a commonplace and effective management strategy in greenhouses worldwide, but in field-grown vegetable crops biocontrol of TSSM is poorly developed. 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 in North Carolina. These studies have determined the environmental and operational factors contributing to successful augmentative biological control of TSSM, including release rates and timing, predator dispersal, the extent of management beyond release points, and predator compatibility with various pesticides. Additionally, natural populations of P. persimilis have established in central NC and successfully overwinter, reoccurring yearly in late summer. 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 staked field tomatoes, which is a promising option for growers to manage TSSM in tomatoes in the southeast United States.