مدیریت شیمیایی بیماری سفیدک داخلی توتون

Cultivation of tobacco to produce tobacco products with the aim of increasing the share of domestic tobacco consumption in the production of domestic cigarettes and exports is one of the basic needs of the country. Tobacco downy mildew disease with Peronospora tabacina is one of the most important diseases of this plant in different parts of the world and Iran which causes significant damage, especially in seedling nursery. The use of fungicides along with other methods of prevention and control has a special place in the integrated management of this disease. In this research, the effect of the new fungicide copper oxide + metalaxyl SC31.8% (Nordoxil) was studied in comparison with the fungicides mancozeb (Ditan M45) and metalaxyl + mancozeb (Ridomil MZ) on this this pathogen in tobacco (Barley variety) under nursery and field conditions. The experiments in the nursery in the form of a completely randomized design and in the field in the form of a completely randomized complete block design with seven treatments (including three doses of 1, 1.5 and 2 liters per hectare for Nordoxil, Ditan M45 at the rate of 2.5 per thousand, Ridomil MZ at a rate of two per thousand, water spraying and without water spraying) was performed by four repetitions in two regions (Mazandaran and Gilan provinces). Disease severity index data were recorded based on CORESTA scale. Then, the area under the disease progression curve and disease control percent (DCP) was calculated and used for statistical comparison of the treatments. The results showed that the different experimental treatments in both the nursery and the field are significantly different from each other. Comparison of the means showed that the efficacy of Nordoxil fungicide at doses of 1 liters per hectare for controlling tobacco downy mildew in the nursery was lower compared to Ridomil MZ and Ditan M45 fungicides; but the dose of 1.5 liter per hectare of this fungicide was effective on controlling this disease in the nursery with 75% efficiency. In the field, to achieve the desired and similar result to Ridomil MZ, nordoxil should be used in the concentration of 2l/ha (with 81% efficiency in disease control) or at least in the dose of 1.5l/ha (with 76% efficiency in disease control). In general, it is recommended to use Nordoxil fungicide at a dose of 1.5l/ha in nursery and field conditions as an alternative or in rotation with Ridomil MZ fungicide to control downy mildew of tobacco.