سبب‌شناسی عارضه چوب‌پنبه‌ای شدن و ریزش میوه آلو در باغات خوانسار (استان اصفهان)

Recently, a disorder as corking of some parts of the fruit and fruit falling in the plum orchards of Khansar County (Isfahan province, Iran) has caused serious damage to the gardeners. Viral diseases (such as plum pox virus) and fungi (such as powdery mildew, molinium blight and peach leaf curl) can potentially cause fruit falling in stone fruits. Damages due to some pests (such as plum fruit moth, aphids, thripses and mirid bugs) can lead to fruit falling and/or deformity. In this study, the role of various factors in the occurrence of the disorder was investigated, by weekly sampling from early spring to mid fall. For this purpose, from fruiting stage, fruit samples from the symptomatic trees were collected and then cultured on a wet environment and on PDA and NA media, for presence of fungi or bacteria. To investigate viral diseases, the leaves of the symptomatic trees were sampled and then sent to Iranian Plant Protection Research Institute to detect the virus. To investigate the role of insects in the occurrence of the disorder, from fruiting stage, orchards were visited and active insects were collected on symptomatic trees, using shaking method. Then, in the laboratory, the insects were separated and identified. In each orchard, four trees were selected and on two branches of the trees, all active insects except the slightly insect were removed, and then these branches were covered with a lace sleeve. At the same time, on the two other branches of the same trees, all active insects were completely removed, and then these branches, as control, were covered with a lace sleeve. The amounts of fruit falling within these sleeves were determined at the end of the season. To investigate possible association of the slightly disorder with nutritional problems, leaves and fruits of the symptomatic and symptomless trees were collected and sent to the laboratory to determine the concentration of nutrients (calcium, potassium and magnesium). The results showed no growth of fungal or bacterial agents on the media. In the branches covered with lace, the symptoms of fruit corking and falling were observed, indicates that the insect does not interfere with the disorder. There was no difference in the amount of nutrients between symptomatic and symptomless trees. Study for associated of plum pox virus (PPV) in the symptomatic trees are under consideration, In addition to the formation of small pox (fruit corking) and fruit falling, yellowing of the veins and mild mosaics were observed, especially on the suckers in early season. The average percentage of fruit falling in lace sleeves were 80.9-98 % for symptomatic trees and 11.1-17.4 % for symptomless trees.