Grape Anthracnose

When it comes to grape anthracnose, I believe many people don’t know what kind of disease it is. In fact, grape anthracnose is a common fruit disease that occurs in all grape-growing regions in my country. Generally speaking, it is very harmful to grape fruits, especially in the southern region. This disease can easily cause grape flowers to rot. So how can we prevent grape anthracnose? How can we protect grapes from being harmed by the disease?

The main characteristic of grape anthracnose is that the disease will only occur when the grapes are close to maturity. Generally, small spots the size of a needle will appear on the surface of the fruit. After that, the spots will gradually become larger, directly producing small black spots, and even large-scale rot will occur. Below I will give you a detailed introduction to the disease of grape anthracnose.

Grape Anthracnose

Grape anthracnose, also known as late rot, is common in grape producing areas in China. The damage to the fruit is quite serious; in the hot and rainy areas in the south, it can also cause grape flower cluster rot in early spring.

Disease symptoms

It mainly harms fruits that are close to maturity, so it is also called "late rot" pathogen. It attacks the fruit stalks and ear axes, and the fruit grains at the tips of the ears close to the ground are first infected.

When the fruit is infected, small brown circular spots the size of a needle head appear on the fruit surface first. Later, the spots gradually expand and become sunken, and many small black spots arranged in a ring-like pattern appear on the surface, which are the conidia disks of the pathogen. Its most obvious feature is the pink gelatinous conidia that emerge when the weather is humid. In severe cases, the lesions can spread to the entire fruit surface. In the later stage of the disease, the fruit will become soft and rot and fall off, or gradually lose water and shrink into dead fruit. The fruit stalks and panicle axes become infected, producing dark brown oblong sunken spots. In severe cases, the entire panicle of fruits may dry up or fall off.

Pathogen characteristics

Anthracnose is caused by infection by Colletotrichum gloeosporioides, a member of the subdivision Ascomycota and genus Colletotrichum. Under open field conditions, the pathogen mainly overwinters in the form of mycelium lurking in the cortex of the tree, with the largest number found around the nodes of branches and vines. In May and June of the following year, when the temperature rises above 20℃, the fungus-carrying branches and vines will form a large number of spores after being wetted by rain. The most suitable temperature for spore formation is 25℃-28℃. Spores will not be formed below 12℃ or above 36℃. The pathogen spores are spread by wind and rain, germinate and infect. The pathogen invades the epidermal cells of young fruits through small holes in the peel. After a latent incubation period of 10-20 days, lesions will appear. This is the initial infection. For some varieties, after the pathogen invades the young fruit, symptoms do not show until the fruit begins to mature. The pathogen can also invade leaves, new shoots, tendrils and other tissues, but no lesions appear and no abnormalities are observed. This is a latent infection, and the new shoots carrying the bacteria will become the source of infection next year. When the grapes are nearly ripe, the disease peaks when rainy weather occurs. The diseased fruits can continuously release conidia, repeatedly re-infecting and causing the epidemic of the disease.

Mode of transmission

The overwintering pathogen begins to form conidia in June and July and is spread to the fruit clusters through wind, rain and insects. In normal years, the disease begins to occur in early July and reaches its peak in August. The pathogen can invade the host directly through the host epidermis, pores or wounds. The occurrence of the disease is closely related to rainfall. The earlier the rainfall, the earlier the disease occurs. In rainy years, the disease is more severe. Varieties with thin peels are more seriously affected. Early-maturing varieties can avoid diseases to a certain extent due to their early maturity period, while late-maturing varieties often have more serious diseases. Heavy clay soil, low terrain, poor drainage, too low fruit-setting position, extensive management, and poor ventilation and light transmission can all lead to serious occurrence of diseases.

Conditions of disease

The pathogen mainly overwinters in the form of mycelium in the annual branches and vines of the tree. In the spring of the following year, it spreads in large quantities with wind and rain, latently infecting new shoots and young fruits. When the temperature is between 20℃ and 29℃, spores will appear within 24 hours. The disease often breaks out in the summer when grapes are coloring and ripening; the disease is more likely to occur a few days after rainfall, and the disease does not spread significantly during drought. Sun-scalded grapes are easily infected with anthracnose; the cultivation environment has a significant impact on the occurrence of anthracnose. The disease is more severe in vineyards with dense rows and double racks, and less severe in orchards with wide rows and sparse plantings; excessive nitrogen application will cause more severe disease, and the application of potassium fertilizer can reduce the incidence; the disease first occurs in the lower layer of the plant, especially the fruit clusters close to the ground, which become infected first and then spread upward. The disease is less severe in sandy soil and more severe in clay; the disease is more severe in low-lying terrain, waterlogging or poor air circulation.

Prevention and treatment methods

(1) In autumn, diseased branches, diseased ears and diseased fruits on the shelves should be completely removed and burned in a timely manner to eliminate the source of overwintering fungi. (2) In autumn, diseased branches, diseased ears and diseased fruits on the shelves should be completely removed and burned in a timely manner to eliminate the source of overwintering fungi. (3) Strengthen cultivation management, timely pinching, tying vines and weeding to create good ventilation and light conditions for the plants. At the same time, pay attention to reasonable drainage and irrigation to reduce the humidity in the orchard and reduce the severity of the disease. (4) Prevention: Dilute the solution of O-Like (Quick Clean) 300 times and spray all over the plants. The number of times the medicine is applied depends on the specific situation, and the general interval is once every 7-10 days. In the early stage of discovery, use 50ml of quick-cleaning agent + 15ml of garlic oil, add 30 kilograms of water and spray, use it for 2 consecutive days. In the middle and late stages of the disease: use 75ml of Aoli-Kesujing + 15ml of garlic oil + a highly systemic chemical agent, add 30 pounds of water and spray once every 3 days, use 2 to 3 times in a row, and the disease can be controlled. (5) Bagging the bunches is an effective measure to prevent grape anthracnose. The time for bagging should be early rather than late to prevent latent infection of early young fruits. Especially for high-quality table grapes that are not resistant to diseases, bagging is a very valuable measure, which not only protects the grapes from anthracnose infection but also keeps them free from pesticide pollution. (6) Spray 100 times diluted 40% thiram or 3 degrees Baume lime sulfur mixture plus 200 times diluted sodium pentachlorophenol or 800-1000 times diluted 38% cypermethrin to eliminate overwintering pathogens. Starting from late June to early July, spray the medicine once every 15 days, for a total of 3 to 4 times. Commonly used agents include: 800-1000 times diluted 50% Tuibunte, 600 times diluted Jinguojing, 750 times diluted 70% Xingnong Zhenglu, or 600-800 times diluted 56% Aminomycin-methyl, or 800 times diluted carbendazim-Jinggangmycin. Spray the fruiting mother branches carefully. Tuijunct is a drug with a long residual effect and its use should be stopped one month before harvest.

After reading the above detailed introduction to the fruit disease grape anthracnose, I believe that all fruit farmers have a general understanding of the prevention and control of this disease. Grape anthracnose can actually be prevented and controlled through certain means. First of all, we must strengthen cultivation and management, promptly remove diseased and damaged branches on the shelves, pay attention to creating good vineyard conditions, and strengthen irrigation, etc., so as to prevent the disease from harming the grapes.