Evaluation of the correlation between the frequencies of PVY infected plants and the aphid population in seed potato fields of Hamedan province

In this research, during 2008 growing seasons, using the yellow water traps, the seasonal changes of population density of winged aphid species, especially Myzus persicae as the most important virus vector species, was studied. These studies were done in two major areas of seed potato production (Kabudrahang and Razan) in Hamedan province. In each area one field selected and in each field four traps were placed. The traps were five meter apart from each other and their heights of the traps was 60 cm (a little higher than potato plants). Each year the traps were placed in the selected fields from April and the trapped aphids in each trap were collected weekly, until the end of the growing season (end of October). The collected aphids were transferred into the tubes contaning 75% alchohol and 5% glycerin. Using the indentification key (Blackman & Eastop, 2000) the collected aphids were then identified. The identified aphid species were as follows: The species Therioaphis trifolii which comprised 66%-71% of the trapped aphids was the most prevalent species in the all areas studied. The species Myzus persicae, Aphis gosypii, Acyrthosiphon pisum and Macrosiphum euphorbiae were trapped with lower population density. The results indicated that Myzus persicae, as the most efficient vector of PVY, comprised 6% and 1.2% of the vector aphid population in Razan and Kabudrahag, respectively. To determine any correlation between the infection rates of potato plants to PVY and the vector activity, the fields in the two areas were inspected for any PVY infection. The inspections (two times) were done based on the standard method for seed production systems. The aim of the first inspection that was done immediately after emerging the plants, was to determine any primary infections resulting from infected seeds. The results of this inspection showed no infection to PVY in both areas. The second inspection for determining the infections resulting from vector activity was done during the growing season. The results of this inspection indicated that in Razan where Myzus persicae comprised 6% of the aphid vector population, the infection rates of potato plants to PVY was 0.95% and in Kabudrahang where the population of Myzus persicae was 1.2%, the infection rates of potato plants to PVY was 0.25%. Regarding to these results it seems that there is a correlation between the infection rates of potato plants to PVY and the vector activity.