How different strawberry varieties and miticides affect TSSM and predatory mite populations

The twospotted spider mite (TSSM) is the key pest for field grown strawberries in Florida. The standard method of TSSM control is to use acaricides; however, reliance on this tactic is problematic because of issues associated with resistance and effects on non-target organisms.  Tolerant strawberry varieties could reduce the need for frequent application of acaricides. Furthermore, the predatory mite, Neoseiulus californicus McGregor is recommended for use in strawberry IPM programs in combination with reduced risk acaricides and resistant varieties. The objectives of this study are to evaluate 1) the effect of four strawberry varieties on TSSM populations, disease incidence, and yield; 2) the efficacy of three miticides on TSSM populations; and 3) the effect of these miticides on N. californicus. The experiment was a randomized complete block design with four replicates. The four strawberry varieties evaluated include Festival, Radiance, Sensation, and Winter Star. Four acaricide treatments were evaluated following the variety experiment and included Acramite, Abamectin, Nealta, and an untreated control. Four trifoliate leaves were collected weekly from each plot and inspected for TSSM and N. californicus populations. Disease incidence and marketable yield was measured. TSSM populations were higher in Festival; however, Festival had lower disease incidence and higher strawberry yields compared with Sensation. Nealta and Acramite applications resulted in lower TSSM populations. Predator densities were not significantly reduced with applications of Nealta. Therefore, we recommend that Nealta could be applied to tolerant strawberry varieties like Festival in conjunction with predatory mites to minimize TSSM damage and maximize marketable yields.