In order to study the efficacy of Sunn pests' parasitoid flies, four overwintering sites of Sunn pest in Isfahan, including mountains of Kolahghazy, Panjeh, Jozdan and Sacepid were selected and from each site four different elevations were designated as sampling sites. During 1997, at least 6 and, in 1998, three samples were taken at each sampling site. In spring 1998, four wheat and barley fields were selected from Mahyar, Zeyar, Shahinshahr and Lavark regions and from each field eight samples were taken. In order to observe the larvae of parasitoids and to determine their efficiency, 100 Sunn pests were dissected from each sampling unit of aestivation, overwintering, wheat and barley fields.
The parasitism of prevalent species (Phasia subcoleoptrata L.) in spring 1998 was 15.39% for the 1st generation and 1.5% in 1997 and 3.5% in 1998 for the second generation of the pest. All other parasitoid species parasitized less than 1% of the pest population. In some regions, such as Lavark and Zeyar, chemical application against nymphs of Sunn pest were accomplished in spring 1998 at the peak of adult activity of parasitoids' 2nd generation. This application had negative effects on the population of parasitoids but in Shahinshahr where chemical application was accomplished at pupal stage of parasitoid, it did not have any direct adverse effects on the population of dominant parasitoid.
