Egg Parasitoids of the Sunn Pest, Eurygaster Integriceps, and Percentage of Egg Parasitism in Coraim Region, Ardabil Province

The sunn pest، Eurygaster integriceps Puton، is a serious pest of wheat in Coraim region of Ardabil province. In this study، the egg parasitoids of sunn pest was collected and identified in this region during 2007 and 2008. Also، the percentage of egg parasitism was determined in 14 different defined areas in this region. The areas 1-3 were selected in irrigated wheat fields in the presence of different species of trees in the margin of fields and the areas 4-14 were selected in rain-fed wheat fields with no trees in the margin of fields. In each defined area، 10 quadrates (1*1 m) were randomly sampled weekly after migration of overwintered adults of the sunn pest to the wheat fields from stem elongation to ripening stages. Two parasitoid species، Trissolcus grandis Thomson (Hym.: Scelionidae) and Ooencyrtus telenomicidia (Vassiliev) (Hym.: Encyrtidae)، were identified as the egg parasitoids of the sunn pest in this region. It appeared that T. grandis had the highest frequency in the areas 1-3 (irrigated wheat fields in the presence of different species of trees in the margin of fields)، whereas the amount of O. telenomicidia was higher than T. grandis in the areas 4-14 (rain-fed wheat fields with no trees in the margin of fields). The results of field studies indicated that the percentage of parasitism in the areas 1-3 was significantly higher than that on the areas 4-14 during two studied years. Also، the results of this research indicated that the percentage of parasitism varied during different growth stages of wheat and sequential years. That is، the number of laid eggs was higher and the percentage of parasitism was lower in the beginning of anthesis while the number of laid eggs was lower and the percentage of parasitism was higher during the late milk until dough development. These results can be useful in integrated management of the sunn pest in this region.