The effectiveness of the predatory mite, Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae), as a suppressive agent of the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), was evaluated on greenhouse cucumber at predator:prey release ratios of 1:5, 1:15, and 1:30. Releases at each predator:prey ratio were made at 30 T. urticae densities per leaf. Evaluation was initiated 4 days after the release. On the under side of the leaves which were selected randomly from the lower, middle, and upper parts of the plants, the eggs and active forms of T. urticae and P. persimilis were counted using 10X hand magnifier for each treatment. In control treatments without predatory mite and acaricide application, population of T. urticae was constantly increased and reached 140 active forms/leaf in August. Subsequently the population decreased when the plants died. At ratios of 1:5, P. persimilis reached 8 active forms/leaf while T. urticae populations reached 11 active forms/leaf. At ratios of 1:15 P. persimilis population increased (3.4 active form per leaf) and T. urticae population decreased (1.6 active forms per leaf) in September and the latter one was kept by P. persimilis at low levels thereafter. Plant damage also was significantly reduced at these densities. P. persimilis population decreased when prey (T. urticae) population decreased. Our work demonstrates the potential of P. persimilis to provide effective control of T. urticae on a greenhouse-grown cucumber at a moderately low predator:prey ratio (1:15) in Tokat Province, Turkey.

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A total of 17 isolates of entomopathogenic fungus (Beauveria bassiana) were tested against adult females of the two-spotted spider mite (Tetranychus urticae Koch) under laboratory conditions. Spore suspension was prepared from 15 days old culture of the isolates on PDA medium. The fungal surface was scraped using a sterile loop with 10 ml of sterile distilled water having 0.02% Tween 80. Spore concentration of the filtrate was determined using a Neubauer Hemocytometer. This served as a stock suspension. In the pathogenicity tests 5 × 10 6 conidia ml -1 was used. Inoculation was performed by spaying spor suspension directly on the adult female mites. Inoculated mites were transferred on bean leaf disks in sterile petri dishes and incubated under room conditions at 25 ± 2°C and 65 ± 5% RH for ten days. The mite sprayed with sterile distilled water having 0.02% Tween 80 were used as control. Mortality was noted daily. Dead mites were kept separately in humid sterile Petri dishes for another 10 days to determine the mycosis rate. Three isolates with higher mortality or mycosis rates (F-12, F-53, and F-56) were selected for dose-mortality tests. Spore suspension of the isolates at five different concentrations, 1 × 10 4 , 1 × 10 5 , 1 × 10 6 , 1 × 10 7 , and 1 × 10 8 conidia ml -1 , was prepared and tested for its efficacy on adult females of two-spotted spidermite. The experiments were carried out with 3 replications and 10 adults were used for each replicate. In single dose trial, all isolates caused mortality to T. urticae adults. Different mortalities resulting from different isolates of B. bassiana were observed with the concentration of 5 × 10 6 conidia ml -1 and varied from 32.5-72.5% at the end of 72 h incubation period. Mycosis ranged between 2.5% and 40.0%. In dose-mortality trial, isolate F53 caused the highest mortality percentage of T. urticae adults, followed by F-12 and F-56. The effectiveness of these isolates was not significantly different at the concentration of 1 × 10 8 conidia ml -1 . Concentration of conidia affected the mortality of the mites differently (P < 0.05). The results showed that mortality and mycosis were dose dependent which increased with enhancing the spore concentration of the isolates. Mortality ranged between 43.3% and 83% on isolate F-53 from 24 h to 72h incubation period at concentration of 1×10 8 conidia ml -1 . Followed by isolates F-12 and F-56 with 78.3% and 76.7% mortality rates, respectively. Maximum percent mycosis of 43.33% was recorded on 10 th day after treatment with the concentration of 1×10 8 conidia ml -1 ; in contrast to this minimum percent mortality of 3.33% was obtained by the application of the lowest concentration 1×10 4 conidia ml -1 at F-53 isolate. The present results demonstrated that the entomopathogenic fungi isolates of B. bassiana could be used as an alternative for the control T. urticae.

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