In the laboratory the relationships between Western Flower Thrips (Frankliniella occidentalis, WFT), two-spotted spider mites (Tetranychus urticae, TSSM) and the predatory mite Amblyseius cucumeris were studied. The experiments were carried out in a pot-cylinder system with a single bean plant. The results showed that: (1) Adding 40 WFT to 10 TSSM decreased TSSM density by ca. 20% compared to 10 TSSM only. (2) The webbing of TSSM reduced emergence rates of WFT, especially at TSSM high densities. (3) High TSSM densities, leading to intensive webbing, forced the majority of WFT to pupate on the leaves and not in the soil. (4) At low TSSM densities a predator - prey ratio of 1:4 lead to effective control of TSSM by A. cucumeris; however, at high TSSM densities the same predator - prey ratio did not lead to an efficient control of TSSM. (5) Mixed infestations of TSSM and WFT lead to a significantly increased control of TSSM but not of WFT by A. cucumeris.
Species 1: Thysanoptera Thripidae Frankliniella occidentalis (western flower thrips)
Species 2: Acari Tetranychidae Tetranychus urticae (twospotted spider mite)
Species 3: Acari Phytoseiidae Amblyseius cucumeris
Keywords: predatory mites, biological control
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