Testing for non-target effects of spinosad on twospotted spider mites and their predator Phytoseiulus persimilis under greenhouse conditions

The compatibility of the selective insecticide spinosad ( Conserve SC(R)), at rates recommended for thrips control in greenhouses, with release of the predatory mite Phytoseiulus persimilis Athias-Henriot ( Acari: Phytoseiidae) to control spider mites, was investigated in a crop of ivy geranium Pelargonium peltatum, cultivar 'Amethyst 96.' Plants were inoculated with twospotted spider mites, Tetranychus urticae Koch ( Acari: Tetranychidae), 2 weeks before treatments were applied. There were three treatment variables, each at two levels: predators ( released or not), spray application ( water or Conserve SC(R) at 2 ml/3.79 l), and timing of spray ( 1 day before or after predators were released). Twospotted spider mite populations then were sampled twice each week over a three-week period. The application or timing of spinosad had no effect on the ability of the predator to reduce the population of spider mites. Spider mite populations in the no-predator treatment continued to expand over the course of the experiment, while those in the predator-release treatment declined. We conclude that P. persimilis can be used in conjunction with spinosad on ivy geraniums without causing obvious detrimental effects to this predator or leading to a reduction in biological control.