Ali Salehi Sardoei - Southern Kerman Agricultural and Natural Resources Research and Education Center, AREEO, Jiroft, Iran
Azadeh Alizadeh - Faculty of Plant Production, Gorgan University of Agricultural Sciences and Natural Resources, Iran
Afshar Fallah Imani - Department of Horticulture Science, Arak Branch, Islamic Azad University, Arak, Iran

Cold and Freezing stresses cause harmful and devastating damage to many agricultural and horticultural crops. In early December of this year (۲۰۱۶), the occurrence of frost stress led to damage to citrus orchards in the north of the country, especially in the east of Mazandaran province. Investigating and calculating the damage to the orchards after the occurrence of cold and/or frost stress is one of the first actions of the Ministry of Jihad Agricultural and its subordinate organizations. However, the exact estimation of the orchards is one of the problems in this area. that considering the harvest season of the main citrus crops of the province hadn't yet started (Thomson orange) and the fruits were still on the tree (half ripe), the amount of frost damage increased. Due to the sustainability of the tangerines, especially Unshiu, the amount of damage to the fruits was little or few. In addition, the result of evaluating frost damage to citrus trees showed that the amount of leaves and fruit damage in the young trees was much more than in the older trees. The amount of fracture of trunks and main branches caused by snowfall was much higher in the hillsides and foothills compared to the plains. According to the calculated observations, it was found that the amount of damage to Thompson oranges in the cities of Babol, Ghaemshahr and Sari was higher than in the other regions due to a decrease in the air temperature to -۴ degrees C and a longer glacial period. The fracture of the trunk and main branches of the citrus tree in the cities of Ghaemshahr and Babol was more than in the other regions. Also, the dryness of Thomson orange leaves in the cities of Babol, Ghaemshahr and Sari was more than in the other regions. The leaves and fruits of Page tangerines were damaged to different degrees, but Unshiu tangerines weren't severely damaged in this event.

Citrus, Damage calculation, Damage tissues, Freezing stress, Mazandaran province