Epidemical occurrence of Pileolaria terebinthi on Pistacia khinjuk in eastern forests of Khuzestan Province

During surveys conducted in summer and autumn of 2005 on khinjuk trees (Pistacia khinjuk Stocks.) in Eizeh region and Deli village in the eastern part of Khouzestan province, disease symptoms including leaf necrosis, early defoliation, dieback, deformation and hypertrophy of branches were observed on khinjuk trees. Forests showed a vast epidemical expansion of the disease during 2005 and 2006 and in almost all infected trees, complete necrosis of leaves, die back and deformation of branches were observed. Samples were taken from the diseased trees. Microscopically measurements and morphological and histological studies led to identification of Pileolaria terebinthi (DC.) Cast., as the causing agent of pistachio rust in Khuzestan province. Rust attack due to Pileolaria terebinthi has already been observed on Pistacia mutica in Fars Province. The rust is autoecious and its expansion as an epidemic disease on Pistacia khinjuk has been observed in Khouzestan in the recent years. The disease could be a threat to the survival of the valuable genetic resources in the region. Therefore, it is necessary to investigate various etiological aspects taking into account region height, age of the trees, their susceptibility, ecosystem sequencing or region climatic changes in order to exert forecasting and controlling strategies of disease which is spreading northward in the country.