Action thresholds are traditionally based on the density of pests and the economic damage they cause to crops. Pest damage assessments are usually made in a “sterile” environment, devoid of extenuating factors such as predators, parasitoids, and alternative food sources. Recently, the effects of a predator or parasitoid species have been considered. However, interactions between natural enemy species (intraguild predation and interference), which are common in agricultural fields, have not been incorporated yet into decision-making tools. We conducted a series of leaf disc and potted plant trials to evaluate the effects of two predator species, the anthocorid Orius laevigatus (Fieber) and the phytoseiid Neoseiulus cucumeris (Oudemans) on the density of and fruit damage inflicted by western flower thrips, Frankliniella occidentalis (Pergande). We then used the obtained results to develop a pest management decision-making tool for the control of western flower thrips. Because strawberries (Fragaria × ananassa Duchesne) flower in cycles, pollen, a food source for both predators and the pest, is periodically available in the system and has also been incorporated in our decision-making tool. The developed new management tool would allow the relaxation of the economic threshold (ET) for western flower thrips in strawberry flowers. The presence of an average of a single O. laevigatus per flower for example, may allow that relaxation of the ET by 40% (from 10 to 14 western flower thrips per flower) when pollen is available during the winter. Because field monitoring shows that O. laevigatus populations in Israeli strawberry often reach mean densities of three to four per flower, the new approach promises to drastically reduce the employment of toxic insecticides.
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Vol. 103 • No. 4