Distribution and abundance of species of the genus Orius in horticultural ecosystems of northwestern Italy

The genus Orius Wolff includes generalist predators revealed to be very effective in thrips control worldwide. During the years 2005-2007, Orius species were sampled on some horticultural crops (strawberry, sweet leek, and sweet pepper), and on wild flora surrounding crops to identify alternative host plants in Piedmont, northwestern Italy. In the three-year survey, Orius horvathi (Reuter), Orius laevigatus (Fieber), Orius majusculus (Reuter), Orius minutus (L.), Orius niger Wolff, and Orius vicinus (Ribaut) were collected on crop and non-crop plants in the surveyed area. On pepper, the major number of species was recorded, depending on environmental and cultivation conditions. O. niger was the predominant species on strawberries and wild flora, while O. majusculus was the primary species on sweet leek. By contrast, O. laevigatus was never found on the crops, and rarely collected on wild flora in the areas where it has been usually released. On the wild flora larger amounts of Orius were sampled on Galeopsis tetrahit L., Medicago sativa L., Malva sylvestris L., Matricaria chamomilla L., Urtica dioica L., Carduus sp., Lythrum salicaria L., Erigeron annuus L., and Trifolium pratense L., which proved to be important sites for population development and overwintering. The conservation of plant biodiversity as a whole in and near agro-ecosystems is the most reliable way to achieve beneficial insect populations for an effective crop control.