Evaluation of Amblyseius cucumeris (Acari: Phytoseiidae) and Orius insidiosus (Hemiptera: Anthocoridae) for control of Frankliniella occidentalis (Thysanoptera: Thripidae) on greenhouse tomatoes

The effectiveness of inundative releases of the predatory mite Amblyseius cucumeris (Oudemans) and the predatory anthocorid Orius insidiosus (Say) for control of Frankliniella occidentalis (Pergande) on greenhouse tomatoes was evaluated in terms of the population dynamics of F. occidentalis and its associated biological control agents, and by the levels of fruit damage under greenhouse conditions over the course of two trials. Inundative introductions of A. cucumeris at the rate of one sachet (1000 predatory mites per sachet) per plant were made curatively at 4-week intervals at the mean initial thrips densities (±SE) of 120.8 ± 24.2 thrips per plant. Five weeks after the first introduction, thrips populations in the A. cucumeris release greenhouse were significantly reduced to low levels in both trials in comparison to the control greenhouse where no predators were released. As a result, the percentages of the damaged fruit in the A. cucumeris release greenhouse were controlled at acceptable levels (essentially <3%). Inundative introductions of O. insidiosus at the rate of 10 adults per plant bi-weekly failed to reduce thrips population densities to economically acceptable levels with mean fruit damage levels exceeding 8% 10 weeks after the first introduction of O. insidiosus. According to the thrips densities/fruit damage relationship obtained in this study, 50–75 adult and larval thrips per plant was determined as the threshold when F. occidentalis can cause economic loss in fruit quality.