Two-spotted spider mite (Tetranychus urticae) is an important pest of hop. For its control in Slovenia only few acaricides are registered, and also for this reason the pest already developed the resistance to some active ingredients. In 2015, we used for the first time the predatory mite Neoseiulus californicus against two-spotted spider mite in hop garden in Spodnja Savinjska dolina. The efficacy of the predator was evaluated with counting the mobile stages and eggs of two-spotted spider mite on the leaves of hop on three different heights. The countings were performed four times, namely in all three decades of July and in the first decade of August. For comparison, two-spotted spider mites were monitored in hop plants, where no acaricides were used (negative control), and in hop plants, where acaricides were applied for controlling the mites (positive control). The acaricides we used in positive control were Vertimec Pro (active ingredient Abamectin), and Nissorun 10 WP (a.i. Hexythiazox). In the plants, where we used the biological control agents, the number of mobile stages decreased in the beginning, but afterwards the their number was stable. From the economical point of view, the percentage of hop cones injured from the two-spotted spider mite, is the most important. In all four treatments we classified 30 hop cones from the middle height and 30 hop cones from the highest height in four classes regarding the % of damage caused by two-spotted spider mite. In all four treatments we recorded the highest % of healthy (without injuries) and only slightly injured hop cones (0-5 % injuries). The % of injured hop cones was not statistically different among the treatments (control 25,0 ± 2,7 %, biological control 22,2 ± 6,3 %, FFS1 25,0 ± 5,0 %, FFS2 24,8 ± 5,6 %).
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