Grape brown spot disease occurs mostly in various grape producing areas. There are two types of diseased brown spot disease: brown spot disease and small brown spot disease. Brown spot disease is caused by the infection of Pseudocercosis botrytis, which mainly damages the leaves. The infection point is light brown, irregular horn-like spots in the initial stage of onset, and the disease spots gradually expand, up to 1 cm in diameter, and the disease spots are hazel It turns brown and then becomes russet, with yellow-green periphery. In severe cases, the spots are connected into large spots, the edges are clear, the periphery of the back of the leaf is blurred, and the diseased part dies in the later stage, and gray-brown molds occur when it is rainy or humid.
In some varieties, the diseased spots have inconspicuous rims. Small brown spots are caused by the parasitism of Cercospora fasciculatus. Small yellow-green round spots appear at the infection point and gradually expand into 2 to 3 mm round spots. The diseased spots gradually withered and turned brown and then became tea-brown. In the later stage, a black mold layer appeared on the back of the diseased spots on the leaves.
Infection and pathogenesis
The conidia of the brown spot disease fungus have a long lifespan, can adhere to the surface of branches and vines through the winter, spread by wind and rain, germinate under high humidity conditions, invade from the stomata on the back of the leaf, and the incubation period is about 20 days. In the north, the disease usually starts in June. July to September is the peak season and the rainy season can be repeated multiple times, causing major outbreaks. There were two peak incidences in Jiangsu, Zhejiang and Shanghai, the first in June and the second in August. The occurrence of small brown spots is similar to that of brown spots.
2 Effective measures to prevent the occurrence of grape brown spot
This period is the period when grape brown spot disease occurs frequently, because summer rains are more frequent than normal seasons, and this disease occurs more often in various grape producing areas. What measures can be used to prevent the occurrence of this disease?
Grape brown spot disease is more common in the rainy and humid coastal areas. Generally, the incidence is lighter in arid areas or low-rain years. In poorly managed orchards, it can occur in large numbers in the late rainy years, causing early leaf fall, affecting tree vigor and reducing yield.
Control methods: ① Thoroughly remove the litter and reduce the source of disease. Spray 3 to 5 degrees lime sulfur mixture before germination. ②Reasonable fertilization and scientific pruning. Add multi-element compound fertilizer to enhance tree vigor. Topping and pruning in time, keep ventilated and light. ③ Prevention and treatment by spraying. In areas with severe disease, combined with other disease prevention and control, spray 500 times 50% carbendazim or 600-800 times chlorothalonil alternately between July and September, and spray once every 10-15 days. 65% of mancozeb has phytotoxicity on some grapes, and the concentration should be 1000~1200 times.
3 Don’t panic about grape brown spot
Grape brown spot disease is also called leaf spot disease. The disease of brown spot disease is divided into large brown spot disease and small brown spot disease, which will cause different diseases to grapes.
Grape brown spot disease mainly damages the middle and lower leaves of grapes, and mainly damages grape leaves. The infection point appears irregular angular spots in the early stage of the onset of grape brown spot disease. With the gradual expansion of the disease spots, the disease spots will gradually change from light brown to brown; when the grape brown spot disease is serious, the disease spots will form large areas of spots, and the plants in the diseased parts of the grapes will gradually die in the later period. The grapes will be rainy or humid. , A brownish mildew occurs, and the diseased spots on the diseased part of the grapes will gradually wither and fall early. For grape brown spot, it is caused by the parasitism of Cercospora fasciculatus. The infection point appears yellow-green small round spots when grapes are onset, and gradually spreads to form round spots, tomato small brown spots, and the lesions. Gradually dying and turning brown and then dark brown, black mold layer on the back side of the disease in the later stage of the disease. Grape brown spot disease will produce conidia germination and the development of mycelium in the host requires high humidity and high temperature. Under high humidity and high temperature conditions, the disease will be extremely serious. Grape brown spot disease is more serious in rainy years. When the disease is severe, the leaves can fall off early, which will seriously affect the vigor of the tree and the fruit of the grape crop in the coming year. The pathogen of grape brown spot disease survives the winter safely on the fallen leaves with mycelium and conidia. The conidia are spread by air currents and rain, and infect again. After germination, the conidia invade from the stomata on the back of the leaf. After the pathogen invades the host, when the environmental conditions are suitable, the pathogen will overwinter in the diseased leaf tissue to infect again.
In order to prevent and control grape brown spot disease in time, gardeners should apply pesticides for prevention and control in time. Garden staff promptly pull out diseased grape plants after they are found, and take them away from the planting area for destruction, which can effectively prevent the spread of grape brown spot disease; garden staff promptly clean the fallen leaves in the orchard and conduct centralized destruction to eliminate overwintering. Source of bacteria. Strengthen the management of vineyards and forests, pay attention to the drainage of gardens, and appropriately increase the application of fertilizers to promote the growth and development of grape plants and improve the disease resistance of grape plants. In the early stage of the onset of grape brown spot disease, you should start spraying the Oryc-Sujing 300 times diluted solution in time with the agent, and apply the medicine once every 7 days, which can effectively prevent grape brown spot disease; when grape brown spot disease is mildly onset , Use the drug Sujing 300 times diluted and spray, and apply the medicine once every 5-7 days; when the grape brown spot disease is serious, use Sujing 75ml + garlic oil 15ml, add 30 kg of water for spray, and use the medicine for 3 days. Secondly, it can control the occurrence of grape brown spot in time.