Associations between Frankliniella spp. and Orius niger populations in cotton

The distribution of the Frankliniella species E occidentalis (Pergande) and F. intonsa (Trybom) (Thysanoptera: Thripidae), and of the predatory bug Orius niger (Wolff) (Hemiptera: Anthocoridae), in various organs of the cotton plant, as well as prey - predator interactions between thrips and O. niger were investigated over 6 years in cotton fields in the eastern Mediterranean region of Turkey. The highest number of larvae of Frankliniella spp. were found inhabiting bolls, whereas the adults colonized mainly flowers. The majority of predatory bug nymphs were present on leaves, followed by bolls, whereas O. niger adults visited mostly flowers. The thrips larvae were most likely preyed upon on flowers and squares, and bolls were safe plant parts for thrips, with a low predation rate. An intermediate but relatively high predation rate occurred on cotton leaves. In further field experiments, the effects of insecticide treatment on the relationships between O. niger and Frankliniella spp. were investigated. These trials revealed that a higher correlation existed between the numbers of adult O. niger in flowers and Frankliniella spp. in non-treated cotton fields than in insecticide-treated fields. The proportions of prey/predator in flowers ranged from 1.53 to 19.28 and were below four thrips per predator at most sampling dates in some of the nontreated cotton fields. It is concluded that O. niger is an effective predator that can play an important role in suppressing population increase of Frankliniella spp. in cotton.