عنوان مقاله [English]
Introduction: Fungal diseases are a major problem in the cultivation of grapevine, Powdery mildew disease caused by plant pathogenic fungus, Erysiphenecator is one of the most important and destructive diseases of grape in many countries of the world including Iran. Due to extend viticulture area in Iran and the high prevalence of the grape powdery mildew in vineyards, application of sulfur based fungicides is mainly recommended for the disease control. This study was conducted aimed to investigate the effect of new formulations fungicide of sulfur SC 80% and penconazole EW 20% to control grape powdery mildew disease.
Material and Methods: The experiments were conducted on Askari cultivar as susceptible in Ardabil, KhorasanRazavi and Kohgiluye and Boyer-Ahmad provinces and in vineyards, which in previous years had a history of infected and trees were similar in age and growth conditions. Experiments were carried out in a completely randomized block design with four replications. Treatments were composed of penconazole EW 20% 0.125 ml L-1, sulfur SC 80% 2, 2.5 and 3 ml L-1 and control. The spray was carried out three times, including when the young shoots were between15 and 35cm, before falling flowers and stage of sours. One week after the last spray sampling of leaves and clusters was carried out in four directions main canopy trees randomly in each plot. Efficacy of treatments was evaluated based on infection severity found in 60 leaves and 12 clusters in per plot. To determine the amount of sugar and tartaric acid in the grape fruit, sampling of the healthy and infected clusters were carried out and healthy and infected the samples were then separated into a plastic bag and crushed. Then, the juice wasprepared (fruit juice was obtained from 700 g fruit in each sample).To determine the amount of sugar, hand-held refractometer was used and the amount of sugar was determined in healthy and infected fruit. For the determination of tartaric acid in grape juice titration using sodium hydroxide, 1.0 M was carried out.
To determine the yield of grapes per healthy and infected plants and determination of the quantity of the yield damage caused by the disease, after fruit ripening, all clusters of grapes were picked by hand and weighed. Then in each province data were transformed and statistical analysis of data using SAS software was carried out. The mean comparisons were conducted with Duncan's Multiple Range test and Fisher's Least Significant Difference (LSD) test at the 5% level.
Results and Discussion: Combined analysis of variance studied traits showed that between locations in terms of severity of disease in leaves and fruits, between treatment and locations and treatment interaction in terms of severity of disease in leaves and fruits, yield there was the significant difference. Analysis of variance amounts of sugar and acid concentration in the grapes in Ardabil (Meshginshahar) showed between treatments in terms of the amount of sugar and acid concentration in grape was observed the significant difference. According to the results sulfur SC 80% fungicide at concentrations of 2.5 and 3 per thousand the greatest effect in reducing the powdery mildew disease and increase yield and quality of grapes. Analysis of variance for amounts of sugar and acid levels in the grapes in Ardabil (Meshginshahar) showed highly significant differences among treatments in grape sugar and acid concentration at 1% level. Comparison of means indicated that control treatment (without spraying) had the highest concentration of sugar and acid. In this study, increasing the severity of the disease on the leaves and fruit tended to increased acid concentration in the fruit. In this study, the yield of the grape was decreased depending on the disease severity on the leaves and clusters. In this experiment, increasing the severity of the disease on the leaves and fruit tended to increased sugar amount. The intensity of infection was higher in the leaves and fruits as well as the amount of sugar in sugar increases that were consistent with findings of another researcher.
Conclusions: According to the results and taking into consideration environmental protection, the lowest intensity of infection in the leaves and fruit, the highest yield, the most normal sugar and acid concentration were on the treated plants with the sulfur concentration of 2.5 per thousand. According to the results of this study, spraying sulfur SC 80% in the control programs of the disease to prevent the emergence of resistant races of grape powdery mildew would be desirable.