As the saying goes, "where there are people, there are rivers and lakes", and for grapes, there are viral diseases in areas where there is viticulture. For example, Sunshine Rose will show symptoms such as uneven leaves, leaflets, fan leaves, chicken paw leaves, mottled and white, new shoot flattening, and internode lengthening, which are all caused by grape virus disease. At present, there is no cure for viral diseases, and comprehensive prevention and control can only be carried out through various agronomic measures and auxiliary agents.
Types of grape virus diseases
There are four main types of grape virus diseases: fan leaf disease, leaf curling disease, cork disease and stem pox disease. These are the two most common diseases in most vineyards.
Grape fan leaf disease
Grape fan leaf disease is one of the most widespread and most harmful viral diseases in grape production in mainland China. It is caused by grape fan virus infection in the polyhedral virome transmitted by nematodes, aphids, leafhoppers, etc.
Manifest symptoms
The leaves are asymmetrical, the leaf edges are deepened, the petioles are concave and broad, and the main veins are abnormally clustered and fan-shaped, sometimes with fading green mottles.
The leaves begin to appear with yellow spots (sometimes rings or lines), then develop into yellow-green flowering leaves until the whole leaf turns yellow, and the yellowed leaves gradually turn white and finally fall off.
The new shoots are flattened, the internodes are shortened, the double buds are inched, the joints are inched, and the branches are abnormal and clumpy.
Pattern of onset
The symptoms of grape fan leaf disease are first manifested on relatively independent diseased plants, and then centered on these diseased plants, and then spread outward year by year.
The virus can only be transmitted by being present in the parasitic grape plant and in the living roots that remain in the soil after digging up the diseased plant.
The main vector of transmission is nematodes, aphids, leafhoppers, etc. can also be transmitted, and the spread of this disease requires two conditions, one is that there is a virus source, that is, the infected plant, and the other is the need for a transmission vector.
Grape leaf curl disease
Grape leaf curl disease is another important viral disease in grape production, which is widely distributed and occurs in major wine grape varieties in Europe and the United States. The pathogenic viruses of grape leaf curl disease are complex, and these viruses can cause grape leaf roll disease alone or in combination.
Manifest symptoms
The growth of the diseased plant weakened, and in late summer and early autumn, the lower leaves of the plant rolled downward, and then gradually spread to the whole plant.
The red cultivar turned red between the leaf veins, and the white cultivar turned yellow, and the fruit spike was small, the berry coloration was poor, and the ripening period was delayed.
The root system is stunted, the stress resistance is weakened, and it is susceptible to frost damage, the survival rate of grafting is significantly reduced, and the rooting ability is poor.
Pattern of onset
Grape leaf curl disease is mainly transmitted through the vegetative propagation of shoots and buds and the grafting of poisonous rootstocks (some viruses can be transmitted by mealybugs, etc.).
Due to the semi-latent nature of this disease, it is not easy to be detected in the early stage of diseased plants, and most of the diseased plants show symptoms at the fruit ripening stage, and the leaf symptoms are the most obvious before harvesting and defoliation.
Prevention and control measures
From the perspective of the causes of many grape virus diseases, most of them are due to the transmission of poisonous propagation materials through grafting and cuttings, and individual viruses are transmitted by nematodes, powder, aphids, thrips and other insect pests, and it is extremely difficult to recover after the onset of the disease. Therefore, when planting, it is necessary to keep in mind that prevention is the first priority, and comprehensive control measures should be adopted to control the occurrence of viral diseases.
1. Select disease-resistant varieties and detoxified seedlings
There are some differences in the resistance of different grape varieties to viral diseases, and varieties with stronger resistance should be selected as much as possible.
There is no doubt that the selection of detoxified seedlings is the most realistic and effective prevention method for the prevention and control of viral diseases.
2. Isolate and build a park, not repeating stubble
The planting of detoxified seedlings should be planned in a unified manner, and the garden should be built in isolation, and it should not be close to the conventional old vineyards, let alone mixed. The distance between the old and new vineyards should be 100 meters.
Detoxified seedlings should not be planted in vineyards with heavy cropping, and the interval between replanting should be at least 20 years.
3. Special for production tools
The various instruments used in virus-free vineyards, especially pruning tools, should be managed exclusively and stored in isolation, and should not be mixed with plants in poisonous vineyards. Pruning tools are repeatedly washed after use and disinfected with alcohol.
4. Prevent vector insects in time
Many grape virus diseases are transmitted through aphids, nematodes, etc., so chemical agents should be used in time to prevent and control them, cut off the transmission vector, and reduce the close transmission of viral diseases.
5. Strengthen field management
Scientific field management can help to improve the strength of grape vines, enhance their disease resistance and stress resistance, and effectively reduce the occurrence and epidemic of virus diseases.
Paying attention to the application of organic fertilizer, combined with the application of sea harvest, can play a multiple role in improving the soil environment, balancing nutrition, and stimulating plant wildness.
In the critical period of grape fertilizer, spraying foliar fertilizer containing seaweed extract such as seaweed harvest can play a role in rapidly improving tree potential and activating plant physiological functions, especially the plant endogenous hormones, seaweed polysaccharides, alginic acid and other active substances contained in seaweed extract, which greatly improves the disease resistance of grapes.
In addition, reasonable pruning, scientific fruit retention, and enhanced water management can also help improve the tree's strength. Pay attention to the weather conditions in time and take precautions before bad weather comes.
6. Early treatment
Before or at the beginning of the symptoms of viral disease, various drugs are used in time to blunt the virus. Optional: Spraying.
For vineyards that have been diseased, measures should be taken to strictly prohibit cutting branches from diseased plants for propagation material. It is recommended to destroy orchards with an incidence rate of 100%, and to remove diseased plants in a timely manner for sporadic varieties, and to pay attention to the prevention and control of vectors.