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

The competition between Orius tristicolor (White) and Amblyseius cucumeris (Oudemans), both preying on western flower thrips, Frankliniella occidentalis (Pergande), was assessed. On single leaves in small cages, mortality of A. cucumeris due to O. tristicolor was inversely proportional to thrips density; thrips mortality due to O. tristicolor 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. tristicolor and A. cucumeris could be used simultaneously for biological control of western flower thrips in greenhouse vegetable crops.