Efficacy of two predatory phytoseiid mites in controlling the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on cherry tomato grown in a hydroponic system

Thrips is one of the most harmful insect groups attacking many field and vegetable crops. Predatory mites, especially those in family Phytoseiidae, are considered as good bioagents to control thrips where application of chemical pesticides can be decreased. This work was conducted to evaluate the efficacy of the two phytoseiid mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans), in controlling the western flower thrips (Frankliniella occidentalis, Pergande) on cherry tomato plants in a hydroponic system. The results indicated that both predatory mites were effective in decreasing populations of adults and larvae of F. occidentalis at all of the chosen periods. The mixed effect of A. swirskii plus N. cucumeris (AS + NC) was higher in reducing thrips populations than that when each of them was used alone. Larvae of F. occidentalis were decreased on leaves of tomato plants from 11.2 and 14.5/leaf in the control treatment (no predatory mites) to 4.27 and 3.73/leaf due to the combination of AS and NC after 7 and 15 days, respectively. On the other hand, larvae of F. occidentalis attained levels of 8.75 and 12.83/ five flowers when no predatory mites were applied compared to 2.46 and 1.20/five flowers when adults of AS plus NC were used after 50 and 60 days of releasing, respectively. This study demonstrated that the combination of AS and NC resulted in higher reductions in F. occidentalis without any competition between them.