Effects of Reduced-Risk Insecticides on Three Orchid Pests and Two Predacious Natural Enemies

The toxicity of 2 reduced-risk pesticides, 2% horticultural oil with 0.05% Silwet L-77 and Grandevo (Chromobacterium subtsugae Strain PRAA4-1T), to 2 predators: Metaseiulus occidentalis (Nesbitt) (Acari: Phytoseiidae) and Hemicheyletia wellsina DeLeon (Acari: Cheyletidae), and 3 orchid pests: the two-spotted spider mite Tetranychus urticae Koch (Prostigmata: Tetranychidae), the phalaenopsis mite, Tenuipalpus pacificus Baker (Acari: Tenuipalpidae), and the longtailed mealybug Pseudococcus longispinus (Targioni-Tozzetti) (Hemiptera: Pseudococcidae) were tested. Grandevo did not kill either predator, and it failed to suppress populations of T. urticae and P. longispinus, but it reduced T. pacificus by 84%. The Silwet and horticultural oil mixture caused mortality of at least 82% in all 5 species tested.