The occurrence characteristics of grape diseases and insect pests are: more diseases and less insects. Diseases are generally divided into three categories:
First, mycosis. This kind of disease is the downy mildew, carbon gangrene, white rot, black pox, gray mold, ear stalk brown rot and other diseases that we control every year, among which downy mildew, carbon gangrene and white rot are called the three major diseases of red grapes, which seriously affect the high-quality production of red grapes.
Second, bacterial diseases. For example, root cancer, the bacteria of this kind of disease multiply by division, invade from wounds, water holes or stomata, and often accumulate water in the affected area. In wet weather, sticky bacteria spill out and spread artificially through water, insects and seedlings, and the spread speed is very fast. It is difficult to control this bacterial disease with chemical agents, and the newly-built garden must carry out quarantine and disinfection on grape seedlings to prevent the spread of bacterial diseases.
Third, viral diseases. This viral disease is spread by grafting and cutting plants with viruses, and the common diseases are fan leaf disease and leaf curl disease. This disease is a catastrophic disease that is difficult to control, usually called cancer. Therefore, quarantine should be strengthened, virus-free seedlings should be strictly selected to build gardens, and strong and disease-free trees must be selected for cutting seedlings.
Fungal diseases can be prevented and controlled through comprehensive prevention and control in production, while bacterial diseases and viral diseases are difficult to prevent and control, so attention must be paid when building gardens. Once found, it should be dug out, burned down or buried deeply.
The following focuses on fungal diseases:
First, downy mildew. This is a worldwide grape disease. As long as there are vineyards, downy mildew will occur, and it will be serious in rainy years. Mainly harmful to leaves. In severe cases, new buds, tendrils, spikes, petioles and young fruits may get sick. Under normal circumstances, the disease began in July in our region, and the peak period was August-September before flowering in special years. When the leaf is seriously infected, the leaf will dry up and fall off, damaging the inflorescence, resulting in falling flowers and fruits. Downy mildew overwinters on diseased leaves and branches, and spreads to leaves through wind and rain the next year. The optimum starting temperature is 18℃-22℃ and the humidity is above 95%.
Second, white rot. It is the most serious disease affecting the yield and quality of grapes, which mainly harms the fruits. The diseased fruit has small white spots, and when it is serious, the whole ear will rot, and it will easily fall off with a gentle shake. White rot mainly exists in soil and diseased branches and fruits. Wintering vineyards contain 300-2000 conidia per gram of soil. In the second year, with the spread of wind and rain, the invasion route is mainly wound, but also from the fruit epidermis. Ears and new shoots close to the ground are prone to disease, usually starting in the middle and late June, and entering the peak period after coloring, especially after storms or hail.
Third, anthrax. Anthracnose is the main disease that harms fruits. Grapes are also susceptible to infection before flowering, leading to rot of flower heads and ear axes. Anthrax has the characteristics of latent infection. The pathogen lurks before the previous winter or after invading the green tissue in the spring of that year, and directly invades the peel in May-June in case of rain. When the fruit ripens in July and August, the disease enters the peak period.
Fourth, black pox. Black pox is also a disease that mainly harms fruits, especially stems and leaves, and mainly harms the green parts of grapes. When the fruit is diseased, the diseased spots are dark brown and round, and the middle is grayish white, like bird's eyes. The diseased fruit is small, dark green, hard and sour, and loses its economic value. The pathogen of black pox overwinters in diseased branches, vines, diseased fruits, diseased leaves and other diseased parts with mycelium, and can survive for 3-5 years on the diseased body. In April-May of the following year, new spores are produced and spread by wind, rain and insects. The peak of this disease is from late June to mid-July.
Five, gray mold. Gray mold is a fruit disease of grape after bagging and during storage. In epidemic years, it also harms inflorescences, causing inflorescences to rot. Botrytis cinerea is a parasitic fungus with a wide host range. Many fruits, flowers and vegetables are prone to diseases, and the wintering places are very wide. Pathogens come from diseased fruits, diseased branches, diseased inflorescences and diseased leaves. Even spores may be found in the air. Bacteria are infected by airflow many times. The low temperature and heavy rain at flowering stage will cause the ear to rot and fall off, and then it will get sick during bagging, ripening and storage.
Preventive and control measures:
1. Do a good job in clearing the garden in winter to reduce the source of bacteria.
2. Strengthen orchard management, increase the application of organic fertilizer, improve the disease resistance of trees, and prune them reasonably, pay attention to the ventilation and light transmission of the orchard, and reduce the humidity of the orchard.
3. Chemical control: Before and after flowering, the whole tree should be sprayed with 70% Jiatuo 800 times solution +68.75% Ipoh 1500 times solution or 78% Bokejiashi Le Jia 1200 times solution, with emphasis on spraying fruit ears. Can play a very good control effect.
At present, the pests that are harmful to grapes in our region are chlamydia, midges, sarcophagus, leafhoppers, scarabs, peach fruit borers, cotton bollworms and so on. However, most of these pests occur in the early stage of growth, endangering young inflorescences, leaves and young fruits. At the early stage of growth (before bagging), pyrethroid pesticides can be mixed with fungicides to prevent and control diseases.