During the observations over the stone fruit gardens in Kermanshah province the dec lining fertile trees of peach and nectarine suspic ious to infection by Phytophthora and Pythium and the soil around their foot and shoot were sampled. After culn1ring these sa mples on common and semi-selective med ia, some isolates of Phy10ph1hora and Py!hium (sensu/ala) were obtained. These isolates were identified based on the ir morphological and several physiological characterist ics. Iso lated species included Phytophthora cactorum, Ovalisporangium helicoides, Globisporangium intermedium, Pythium acanthicum, Pythium deliense, Py1hium aphaniderma/11111 and Py thium Group-G. Their pathogenicity was tested on excised shoots in a completely rando mi zed design pattern under laboratory cond ition. Disease development was significantly different among various treatments. Likewise Duncan's multiple range test placed them in va ri ous groups. Although P.acan!hicum ind uced the most disease extens ion but it was placed in one stati sti cal group with P. caclorum and G. inlermedium. 2 other species includ ing P.aphanidermalum and 0. helicoides were placed in the follow ing group. Disease development of P. de/iense and P.group-G had no significant difference with control. This is the fi rst repo rt of P.acanthicum in Iran.
