Sudy on fauna and distribution of parasitoid wasps of cereal aphid and their efficacy and population alternations of wheat field in Kermanshah provinceý

Aphids are of the most important cereal pests and the population of some species sometimes reaches to high levels in wheat fields. In this study different wheat aphid species and their parasitoids(Hym: Aphidiidae and amp; Aphelinidae) were collected and identified in Kermanshah province during 2004-2007. In order to investigate changes in parasitoid wasps population and host aphids Two fields, one in Kermanshah county(Doroud-faraman) with temperate climate and another one in Sarpol-e-zahab with warm climate were selected.Weekly samplings showed that there were mainly five wheat aphid species including: Rhopalosiphum padi, Shizaphis graminum, Sitobion avenae, Diuraphis noxia and Metopolophium dirhodum. Seven Aphidiid and Aphelinid parasitoid species were obtained from reared aphids mummies. The mentioned species were Aphidius rhopalosiphi Destephani-Prez, A. marticaria, A. colemani, P. gallicum, L. fabarum, Aphelinus sp and Binodoxys acalephae. P gallicum was collected on R. padi and this species is reported for the first one in Iran. All of six mentioned parasitoid species are also newly reported from Kermanshah province of Iran. In this research A.marticaria and A. rhopalosiphi were collected on aphids S. graminum and R.padi, and L fabarum, A. rhopalosiphi and Binodoxys sp. Were obtained from rearing of S.avenae mummies. S. avenae with 56% had the highest amplitude and the species D. noxia with 1 % had the lowest amplitude in the aphids population. Among parasitoid wasps collected from different climate provinces in total species A. rhopalosiphi with 33/9% highest frequent species and B. acalephae with 1.8% its lowest frequently is assigned. Population variation and study of the aphid mummy and the percentage emergence of parasitoid wasps showed that the peak activity of A. marticariae in tropical regions in the first decade April and peak activity of A. rhopalosiphi in temperate regions was in the late May. Key words: Cereal Aphids, parasitoid wasps, fauna, population alternations, dominant species