Important Grape Diseases

Important Grape Diseases

Grapes are one of the most important horticultural crops in the country and one of the most important products in terms of domestic consumption, industry and non-oil exports. Iran ranks ninth in grape production in the world and there is a lot of competition between grape-producing countries. Grapes are a sensitive fruit to various pathogens such as fungi, bacteria, viruses, and nematodes.

Grape Powdery Mildew

Grape powdery mildew, true mildew, or superficial mildew is a disease that is found in large quantities in most vineyards in the country. The disease appears as white spots on the upper surface of the leaf in the form of a floury coating and white spots on the tips of the branches that gradually turn brown or black.

The fungus that causes the disease is often found on unripe grapes and causes the clusters to fail to ripen, become sour, and crack. The presence of the disease on trees and clusters reduces the quantity and quality of the product.

Management and control of grape powdery mildew

Vineyards should be established in areas with adequate air flow and sufficient sunlight. It is best to prune excess and dense branches in early spring. In terms of fertilization, excessive use of nitrogen fertilizers increases the severity of the disease.To control grape powdery mildew, it is best to remove weeds, especially under the shade of trees. Some elements, such as fertilizers containing sulfur, are effective in controlling this disease, which is usually used in dry areas as sulfur dust and in humid areas as sulfur tablets. In addition, the use of spraying should be done in three times: the first time: before bud swelling, the next time after shedding petals and fruit formation, and the third time should be done two to three weeks after the second spraying, at the same time as the buds appear. The best fungicides for grape powdery mildew:

80% sulfur fungicide Bahavaran, penconazole fungicide Behavaran or Topas, Belquit, Strobi

Grape Downy Mildew

Internal powdery mildew or false powdery mildew of grape trees is seen in the regions of Ardabil, Mazandaran, Khuzestan, West and East Azerbaijan.

Symptoms of Grape Downy Mildew

Pale yellow, translucent spots with a distinct border appear on the surface of the leaves, which gradually coalesce, turn brown, and dry. On the underside of the infected leaf, on the underside of the spots, spots with a soft, grayish-white fluffy coating are visible. The disease can infect the canes, which are covered with white hairs. The clusters are initially covered with a white hairy coating, becoming leathery and wrinkled when the clusters reach half their final size.

Management and Control of Downy Mildew in Grapes

Planting seedlings in soil with proper drainage and sufficient sun, collecting diseased parts and burning them at the end of the season to destroy overwintering spores, maintaining garden ventilation, keeping foliage dry, and removing weeds.

The best fungicide for grape downy mildew is Captan or Profiler fungicide and Copper Oxychloride fungicide. The best time to spray to combat grape downy mildew is the first time before flowering and the second time 7 to 10 days after the first spraying, in consultation with a plant specialist.

Types of Post-Harvest Grape Diseases

Post-harvest grape rots are caused by fungi such as botrytis cinerea, Alternaria spp and penicillium spp. Symptoms of post-harvest grape rot include discoloration, softening, crushing of the berries and their change to gray, brown, blue and green.

Post-harvest grape disease management and control

Planting grapes in areas with sufficient sunlight, not using large amounts of nitrogen fertilizers, harvesting grapes on dry days without rainfall, harvesting clusters using fruit shears, Set the temperature of the cold storage between 1 and 4 degrees Celsius and create ventilation between the boxes in the warehouse, use sodium fungicides or sulfur pads, one pad for every 5 kilograms of grape clusters.

Grape leaf blight viral disease

Grapevine fanleaf virus, which causes the spread of the disease in areas such as Fars, Kurdistan, Zanjan and Qazvin provinces. This viral disease may be seen in aerial organs such as leaves, branches and flowers in the form of general yellowing, mosaic spot discoloration in the spaces between leaf veins or on the entire leaf. Young leaves and shoots become misshapen, small, and fan-shaped, and yellow to white borders may develop along the veins, called vein banding.

Management and Control of Grape Leaf Blight Virus Disease

Using healthy, virus-free rootstocks and selecting seedlings from reputable nurseries, removing infected seedlings and burning them, eliminating nematodes in vineyards, and disinfecting the soil using sodium metam at a rate of 120 to 220 ml per square meter.

Grape Leaf curl Disease

Grapevine leaf curl disease caused by viruses of the closterovirus genus, the most important of which is GLRv3. The virus is distributed in East and West Azerbaijan and Zanjan.

Symptoms of grape leaf curl disease

Growth retardation, downward leaf curling, smaller and reduced number of clusters, causing symptoms such as potassium deficiency symptoms in the leaves.

Disease management and control

Elimination of virus-carrying pests, use of healthy and certified virus-free rootstocks, removal of diseased seedlings and burning them.

Conclusion

In this article, we learned about the types of grapevine diseases, the causes of grapevine leaf curl, the causes of white spots on grapevine leaves, ways to control them, and the best fungicides for grapevine diseases.