Fauna of cereal aphids and their coccinellid predators and investigation on the efficiency and population dynamics of the dominant species in Kurdistan province

Wheat as the most important crop in Kurdistan province has several pests including aphids.The coccinellids have a fundamental role in controlling aphids. In this research, cereal aphidspecies and their coccinellid predators were identified and the efficiency and populationdynamics of the most abundant species of coccinellids were studied during 2001-2003. Three irrigated wheat fields in Dehgolan and Kamyaran, and one rain fed field in Marivan were selected. Samples were taken weekly and the aphid species were counted in laboratory and the occurrence frequency of each species was recorded. Adult coccinellids were collected by random sweep netting and their relative occurrence was recorded. As results, 7 aphid species were identified which Sitobion avenae F. and Schizaphis graminum Rond. with respectively 66.5 and 30%, have the highest population densities. Also 6 coccinellid species were identified which Hippodamia variegata Goeze and Coccinella septempunctata L. with respectively 60 and 37%, have the highest population densities. Results showed that H. variegata as the most abundant coccinellid species in wheat fields was not able to control the aphids significantly (under this experimental condition) due to very fast reproduction of aphids and in absence of other natural enemies. Therefore, cereal aphids can be controlled by the presence and activities of their natural enemies complex.