Effect of introductions of a predator complex on spider mites and thrips in a tunnel and an open field of pesticide-free everbearer strawberry

BACKGROUND: Chemical control of spider mites and thrips in everbearer strawberry is difficult as few efficient chemicals are available and residues represent a risk. In the north the success of biocontrol of mites and thrips in open fields compared with tunnels needs to be evaluated. OBJECTIVES: To investigate the need for control of spider mites and thrips and evaluate the effectiveness of biological control agents in everbearer strawberry. METHODS: Similar experimental plots, in a tunnel and an open field, planted with three everbearer strawberry varieties were arranged to compare the effect of introductions of the spider mite predator Phytoseiulus persimilis and releases of the generalist predatory mites Neoseiulus cucumeris and Neoseiulus barkeri and a predatory bug, Orius majusculus. Several sampling methods were used to evaluate mite and thrips populations. RESULTS:Phytoseiulus persimiliswas successful against spider mites. Naturally occurring cecidomyiid and staphylinid predators affected control positively. Thrips damage remained mostly tolerable. The dominant thrips species were Thrips major, Thrips atratus, Thrips vulgatissimus and Frankliniella intonsa. Thrips numbers in the beating tray samples correlated with thrips damage to berries. CONCLUSIONS: Predatory mites were effective in controlling spider mites in an open field and a tunnel. The need for thrips control depended on the strawberry variety. Naturally occurring predators contributed to the control of spider mites and thrips.