What are the symptoms of grape downy mildew damage?
Do you know these? For related content about the symptoms of grape downy mildew damage in green plants, please see the detailed introduction below.
What are the symptoms of grape downy mildew damage?
Leaf damage. At the beginning of the disease, irregular lesions will form on the affected leaves, then the lesions gradually become light green, and a white downy mildew layer appears on the back of the lesions. As the degree of damage from downy mildew increases, the lesions gradually expand, the color turns yellow-green, then red-brown, and eventually fall off.
Young shoot damage. Infected young shoots begin to show light yellow waterlogging, with a small amount of mold layer on the surface. As the disease progresses, the lesions tend to expand, changing color from light yellow to brown. In severe cases, the shoots stop growing and show twisted symptoms, leading to death.
Fruit damage. The affected young fruit turns gray, the stem is densely covered with white mold, and when the fruit is larger, brown spots form, growth and development stop, and the fruit cracks in the later stage.
Prevention and control measures for grape downy mildew
Variety selection. In areas with severe downy mildew, such as the south, it is appropriate to plant disease-resistant varieties such as Xiahei, Meirenzhi, and Bailuoshasha. It is recommended that strong-resistant American grape varieties should be planted with rootstock grafting.
Pruning the garden. Grape downy mildew overwinters in the soil, so during winter pruning, special attention should be paid to cutting off the remaining diseased branches and leaves, then transporting them to the orchard for集中 burial or incineration to prevent the diseased leaves from entering the soil to overwinter and reduce the source of insects.
Cultivation mode. With a large planting area of grapes, farmers can adopt a rain-sheltered cultivation method, which can adjust the ripeness of grapes, alleviate sales pressure, and also reduce the soil moisture and air humidity in the vineyard, thus reducing the occurrence and harm of grape downy mildew.
Field management. Field management can increase the application of organic fertilizers, strengthen water management, and maintain the microclimate environment of the field. In addition, bagging technology can be popularized and applied in fruit cultivation. Using glassine bags with good breathability and light transmission can reduce the invasion of pathogens and achieve the goal of uniform fruit, good commercial quality, and high economic value.
Chemical control. The chemical control of grape downy mildew is mainly divided into two stages. Preventive fungicides such as a 1:1:200 Bordeaux mixture or 78% Cobo 600-800 times solution can be used to prevent and control the disease, starting 10 days after the grapes sprout, and spraying every 10-15 days until the fruit is bagged.
If grapes are damaged by downy mildew, internal fungicides such as 80% dimetomorph, 72% metalaxyl, or cypermethrin can be sprayed. At this time, the spraying period should be determined according to the condition of the disease, generally every 7 days.
The above introduces the symptoms and prevention methods of grape downy mildew damage. For grape growers, we need to understand the most basic symptoms and prevention measures to avoid more infections and greater losses.
The above explanation of the symptoms of grape downy mildew damage, hoping to bring a little help to your life!