مطالعه پراکنش بیماری لکه طاووسی زیتون و نقش برخی از اصول اولیه باغبانی در میزان آلودگی به بیماری لکه طاووسی زیتون در منطقه طارم

Tarom region of Zanjan province with an area under cultivation of about 20,000 hectares of olive groves is the most important olive growing center in the country. With the increase in the area under olive cultivation in recent years, Olive Leaf Spot (OLS) disease (caused by Venturia oleaginea) has become a serious problem for the olive groves and it becomes an epidemic every year. In order to study the distribution of the disease in olive orchards of Tarom, in late April and early May (coinciding with the height of the epidemic in region) in 2018 and 2019, 175 olive orchards were investigated in different areas of region and in each orchard 10 bearing olive trees (over 10 years old) of the common cultivar (yellow cultivar) were selected and about 100 leaves were randomly sampled from four sides of each tree and the incidence and infection severity of each garden were determined in lab. Simultaneously with sampling, the geographical coordinates of the orchards were recorded using GPS device and the basic principles of gardening of the mentioned orchards (planting distance, tree height, tree age, proper pruning, irrigation system type, soil texture type and weed management) were recorded in order to determine the correlation and relationship between the incidence and severity of infection of olive orchards with the basic principles of gardening and topographic data of the area using geographic information system (GIS). Results showed that most of the olive groves are receptive to contamination above 60%. The average of infection incidence of olive orchards with OLS was 70.3% at the height of the epidemic. In all sampling areas there was a direct relationship between the infection incidence and infection severity. Analysis of correlation between basic principles of gardening and the infection showed that pruning of trees with + 0.56 and height of trees with + 0.55 had the highest correlation with olive peacock spot disease. Correlation of other parameters respectively was: soil texture type (+ 0.52), tree age (+ 0.45), irrigation system (+ 0.36), weed management (+ 0.31) and planting distance (+ 0.19). Despite the direct impact of topography on the disease, the correlation between sea level elevation parameter and the disease incidence was poor (+ 0.04). The results showed that the lowest rate of infection was in orchards where the ratio of tree height to planting distance was 0.51 and this ratio was 1.19 in orchards that had the highest percentage of infection. The results of this study showed that two important principles of basic principles of gardening: pruning and considering the ratio of tree height to planting distance, have the greatest role in reducing the infection of olive gardens to OLS.