Different releasing ratio of Phytoseiulus persimilis A. H. in biological control of Tetranychus urticae Koch in greenhouse roses

Phytoseiulus persimilis is the most effective natural enemy of Tetranychus urticae under greenhouse condition. Effects of this predatory mite on the rose spider mite were evaluated through three releasing methods i.e. 6 predator per m2, one predator to 10 and 20 of active stages of T. urticae on red and yellow roses varieties in Isfahan during Mid Dec. until late Feb. Releasing was applied when mean no. of 3 active mite stages found of 30% of rose leaves randomly. The factorial statistical method with three replications used to analysis data of the treatments. From each treatment, 30 leaves collected randomly at weekly interval. Eggs and active predatory mite along with active spider mite stages were recorded underside of rose’s leaves with the help of stereomicroscope. The first sign of predatory mite was found at third sampling week in all releasing methods. Mean and rate of spider mite infestation found from 5th week onwards at decreasing rate. Mean of 1.55 predatory mites in releasing ratio of one predator: 10 spider mites caused considerable reduction of spider mite population (0.36±0.25 mites/leaf) and rate of rose infested leaves (6.67%) during 10th week sampling. An increase on mean predatory mites (1.46±0.10) with 100% existence on all collected rose leaves observed at 10th sampling occasion. Comparing the releasing methods indicated that, the ratio of one predator: 10 prey mites with single releasing was the most effective biological control of spider mite under greenhouse rose’s condition.