Biological Responses of Russian Wheat Aphid, Diuraphis noxia(Mordvilko) (Homoptera: Aphididae) to DifferentWheat Varieties

ABSTRACT In recent years, the Russian Wheat Aphid, has been included worldwidely in the list of the important pests of cereals, particularly wheat plants. In addition to direct serious damage, the aphid is the main vector of Barley Yellow Dwarf, Barley Mosaic, and Sugarcane Mosaic Viruses. The pest was reported from East Azarbaidjan province (Iran) a few years ago and it is now widespread in Tabriz, Ahar and Kaleybar wheat fields. In the present study, the possibility of any resistance was looked for at the tillering stage in Sardari, Sabalan, Alvand, Zarrin and Alamoot, the most extensively planted varieties in the province. The experiment was conducted under glasshouse conditions of 24.4±1.6 oC with 50- 60% R.H. and a photoperiod of 14:l0(L:D). Antibiosis was determined by studying the percentage survival of the nymphs, their developmental time, and fecundity (total number of progeny per /female produced within the first 10 and 15 days of the reproductive cycle) calculating the relevant intrinsic rate of natural increase (rm values). The analysis of variance indicated that, regarding the last two parameters, there were significant differences (P<0.05) between the varieties. The highest (43.21±5.45) and the lowest (34.43±8.91) average numbers of progeny within the first 10 days were observed in those reared on the Sardari and Zarrin varieties respectively but the figures obtained within the first 15 days were found to be 49,43±13.31 on Alamoot and 58.86±9.45 on Sardari. Also the highest mean “rm” value (0.3399±0.01) was estimated for rearings on Sardari with the smallest (0.2889±0.03) on the latter. At present, Sardari seems to be more likley susceptible to the aphid amongst the others. Field trials and experiments on later phenological stages of the wheats and potential role of other resistance mechanisms is going on.