Biological control of Tetranychus urticae (Acari: Tetranychidae) with naturally occurring predators in strawberry plantings in Valencia, Spain

Biological control of Tetranychus urticae (Acari: Tetranychidae) with naturally occurring predators in
strawberry plantings in Valencia, Spain
FERNANDO GARCIA-MARI and JOSE ENRIQUE GONZALEZ-ZAMORA

Abstract. Naturally occurring beneficials, such as the phytoseiid mite Amblyseius californicus McGregor and the insects Stethorus punctillum Weise, Conwentzia psociformis (Curtis) and others, controlled Tetranychus urticae Koch in 11 strawberry plots near Valencia, Spain, during 1989–1992. The population levels of spider mites in 17 subplots under biological control were low or moderate, usually below 3000 mite days and similar to seven subplots with chemical control. In most of the crops A. californicus was the main predator, acting either alone or together with other beneficials. Predaceous insects colonized the crop when tetranychids reached medium to high levels. For levels above one spider mite per leaflet, a ratio of one A. californicus per five to ten T. urticae resulted in a decline of the prey population in the following sample (1–2 weeks later). These results suggest that naturally occurring predators are able to control spider mites and maintain them below damaging levels in strawberry crops from the Valencia area.

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