Efficacy assessment of Neoseiulus cucumeris at different release rates in control of Frankliniella occidentalis on rose plants under laboratory and microcosm conditions

Abstract

The effectiveness of predators in suppressing prey populations is known to be influenced by the predator-prey release ratio. The efficacy of Neoseiulus cucumeris (Oudemans) against  Frankliniella occidentalis (Pergand) in the presence or absence of Tetranychus urticae Koch and Phytoseiulus persimilis Athias-Henriot on rose plants was evaluated in the present study. The decrease of F. occidentalis populations was compared at the six predator:prey ratios of 1:2, 1:5, 1:10, 1:20, 1:50, and 1:100 in the laboratory, and at the three release rates of 20, 40, and 100 predators per m2 in microcosm conditions. The plants without predators were considered as controls. All treatments with the release of N. cucumeris resulted in a significant decrease in F. occidentalis larval population compared to the control. The most suppression (84.5%) of F. occidentalis larvae was observed in the release rate of 100 adults of N. cucumeris per m2 in 30 days after the release of the predator. Predator ratios of 1:2 and 1:5 of N. cucumeris: F. occidentalis resulted in a 94.6 and 93.4% decrease in F. occidentalis larvae after 24 hours, respectively. The presence of T. urticae (as a competitor herbivore) and P. persimilis had no effect on the efficiency of N. cucumeris in the suppression of F. occidentalis. The dense webs of T. urticae decreased the efficiency of N. cucumeris at predator:prey ratios of 1:5 and 1:10 more than1:2. This study showed that the release of 100 adults of N. cucumeris per m2 would be sufficient to control F. occidentalis larvae on rose plants. Moreover, we demonstrated that higher release rates of N.cucumeris are needed when T. urticae’s dense webs are present.