ارزیابی تراکم های مختلف رهاسازی Neoseiulus cucumeris و Amblyseius swirskii در کنترل Frankliniella occidentalis روی گیاه رز

The western flower thrips, Frankliniella occidentalis (Pergand) (Thysanoptera: Thripidae), is a major economic pest of many ornamental plants including roses. The efficacy of Neoseiulus cucumeris (Oudemans) and Amblyseius swirskii Athias-Henriot against Frankliniella occidentalis (Pergand) in the presence or absence of Tetranychus urticae Koch on rose plants (Rosa hybrida cv. Vandenta) at Mahallat, Markazi Province, Iran (25±5 °C, temperature; natural light cycle of~14:10 h [L:D], photoperiod; 60±10%, RH) was investigated. The decrease of F. occidentalis populations was compared at the six predators: prey ratios of 1:2, 1:5, 1:10, 1:20, 1:50, and 1:100 in the laboratory, and at the three release densities of 20, 40, and 100 predators per m2 in microcosm conditions. In laboratory assays, two phytoseiid mites decreased F. occidentaliis population at statistically similar rates of 95, 94, 64.5, 56 and 46.5 percent at predators:prey ratios of 1:2, 1:5, 1:10, 1:20, 1:50, and 1:100, respectively. In microcosm tests with infested rose plants, both phytoseiid mites established and significantly decreased F. occidentalis larval population compared to the control in all treatments of release densities (P<0.001). However, A. swirskii was the more effective predator in a decrease of F. occidentallis larvae in all release densities compared to N. cucumeris. The most suppression (84.5%) of F. occidentalis larvae was observed in the release density of 100 adults of N. cucumeris or A. swirskii per m2 over 30 days after the release of the predators. This study showed that the release of 100 adults of N. cucumeris or A. swirskii per m2 would be sufficient to control F. occidentalis larvae on rose plants. Moreover, the dense webs of T. urticae significantly reduced the efficacy of both phytoseiid species in reducing the population of thrips larvae at 1:10 and 1:5 predator:prey ratios, but had no significant effect on predatory mite efficacy at 1:2. Therefore, when dense webs of T. urticae are present, a higher release densities of N.cucumeris or A. swirskii is required.