COMPETITION BETWEEN ORIUS TRISTICOLOR (WHITE) (HEMIPTERA: ANTHOCORIDAE) AND AMBLYSEIUS CUCUMERIS (OUDEMANS) (ACARI: PHYTOSEIIDAE) FEEDING ON FRANKLINIELLA OCCIDENTALIS (PERGANDE) (THYSANOPTERA: THRIPIDAE)

Abstract The competition between Orius tristicoior (White) and Amblyseius cucumeris (Oude-mans), both preying on western flower thrips, Frankliniella occidentaiis (Pergande), was assessed. On single leaves in smail cages, mortality of A. cucumeris due to O. tristicoior was inversely proportional to thrips density; thrips mortality due to O. tristicoior was unaffected by A. cucumeris density. The proportion of A. cucumeris in the prey eaten was consistently less than its proportion in the prey initially available, both when thrips density varied and when A. cucumeris density varied. These relationships held for both immature and adult thrips. These results suggest that O. tristicoior and A. cucumeris could be used simultaneously for biological control of western flower thrips in greenhouse vegetable crops.