M. Hasanzadeh - Plant Pathology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
N. Safaie - Plant Pathology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Islamic Republic of Iran.
M. R. Eslahi - Plant Protection Research Department, Khuzestan Agricultural and Natural Resources Research Center, AREEO, Ahvaz, Islamic Republic of Iran.
S. T. Dadrezaei - Seed and Plant Improvement Department, Agricultural and Natural Resources Research Center of Khuzestan, AREEO, Ahvaz, Islamic Republic of Iran.
S. N. Tabatabaei - Seed and Plant Improvement Department, Agricultural and Natural Resources Research Center of Khuzestan, AREEO, Ahvaz, Islamic Republic of Iran.

In this study, the first symptom appearance of wheat leaf rust disease was monitored in Khuzestan Province every ten days from early December ۲۰۱۴, for three years. Also, the climate changes and their influence on the development of the disease were studied. During ۲۰۱۴-۲۰۱۵, the first symptoms, with the severity of ۵ MS (Moderately Susceptible), appeared in the south and west parts in early and mid-March, respectively. In northern areas, the symptoms appeared with ۱۰ MS severity in early May. In ۲۰۱۵-۲۰۱۶, the first symptoms appeared with the severity of ۵ MS in February in the southern areas. In the west, symptoms appeared and reached ۲۰ S (susceptible) on March ۱۰. In the north, the disease started in late February with the severity of ۱۰ MS and developed to ۳۰ S. In ۲۰۱۶-۲۰۱۷, the first symptoms appeared around the Karun River with the severity of ۵ MS on March ۱۰ and eventually reached ۱۰ MS in late March. In the western areas, the disease started in early March with the severity of ۵ MS and then stopped. Symptoms appeared one week later in the north, with the severity of ۵ MS, and reached ۱۵ MS until the end of March. Based on the previous studies, the first symptoms of wheat leaf rust usually start from the west. However, now, the regional pattern of the symptom has changed dramatically, and it appears in the south near Karun River and the Sugar Cane Crop Industry. This might be due to implementation of preventive measures and dryness of a big part of Hoveyzeh Marshland.

Climate change, Epidemiology, Karun river, Winter wheat.