Preselection of predatory mites to improve year-round biological control of western flower thrips in greenhouse crops |
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Authors: | Yvonne M van Houten Paul C J van Rijn Lynell K Tanigoshi Pam van Stratum and Jan Bruin |
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Institution: | (1) Department of Pure and Applied Ecology, University of Amsterdam, Kruislaan 320, 1098 SM, Amsterdam, The Netherlands;(2) Glasshouse Crops Research Station, P.O. Box 8, 2670 AA Naaldwijk, The Netherlands;(3) Present address: Department of Entomology, Washington, State University, 99164-6382 Pullman, WA, USA |
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Abstract: | In spring and summer, two groups of natural enemies are successfully used for biological control of western flower thrips,Frankliniella occidentalis (Pergande) in greenhouses: phytoseiid mites (Amblyseius cucumeris (Oudemans) and, to a lesser extent,A. barkeri (Hughes)) and anthocorid bugs (Orius spp.). During winter, however, these predators often fail to control the pest. One likely cause for failure is the predators'
tendency to enter diapause under short day conditions. In addition, eggs of predatory mites are generally susceptible to low
humidity conditions, which often arise in greenhouses when outside temperatures drop below zero, or at bright, hot days in
summer. In search for a thrips predator that is not hampered by these conditions, five subtropical phytoseiid species were
selected which were known to feed on thrips:A. hibisci (Chant),A. degenerans Berlese,A. limonicus s.s. Garman and McGregor,A. scutalis (Athias-Henriot) andA. tularensis (Congdon). These species were compared toA. cucumeris andA. barkeri, with respect to the following features: (1) predation and oviposition rate with youngF. occidentalis larvae as prey, (2) oviposition rate on a diet of sweet pepper pollen, (3) drought tolerance spectrum of eggs, and (4) incidence
of reproductive diapause under short day conditions. The results showed thatA. limonicus exhibited the highest predation and oviposition rates on a diet of thrips larvae. Moreover,A. limonicus females showed total absence of diapause under the conditions tested. A major disadvantage of this species was, however,
that its eggs were most sensitive to low air humidity conditions. Least sensitive to low air humidity were eggs ofA. degenerans andA. hibisci. Females ofA. degenerans andA. hibisci also showed total absence of diapause, and intermediate rates of predation and oviposition, on both thrips larvae and pollen.
In conclusion, we argue thatA. degenerans andA. hibisci are the most promising candidates for biological control ofF. occidentalis under conditions of low humidity and short day length. The success of these candidates remains to be shown in greenhouse
experiments. |
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Keywords: | biological control Thripidae Frankliniella occidentalis Phytoseiidae Amblyseius diapause drought tolerance predation oviposition |
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