Natural biological control of Tetranychus urticae Koch (Acariformes, Tetranychidae) on organic strawberries in greenhouse

A case of biological control of Tetranychus urticae Koch by the native Phytoseiulus persimilis Athias-Henriot and the alien Neoseiulus idaeus Denmark & Muma naturally occurred, has been observed in organic strawberries in greenhouse in Sicily during the winter period (December-January). The initial strong infestation of T. urticae (79% of sampled leaves), was reduced to 3% of infested leaves after 4 weeks. During this period, phytoseiids were constantly present on 75.1% of infested leaves (66.7 - 88.9%), but also on 16.4% (4.1 – 28.6%) of the uninfested ones. P. persimilis occupied the 49.2% (27.8-66.7%) of infested leaves whereas N. idaeus the 57.4% (37.4- 66.7%) of them; on 31.5% (13.9-44.4%) of infested leaves both phytoseiids have been recorded. These data showed that the con-presence of the highly specific on T. urticae, P. persimilis with the selective on tetranychids N. idaeus did not hamper the predation activity of both species resulting in an effective control of T. urticae within a short time period.