How to identify grape white rot? What are the prevention and control techniques?

Grape white rot, commonly known as water rot or ear rot, is mainly harmful to ears (including rachis, pedicels and grains), as well as branches and leaves. It is a major disease commonly occurred in grape producing areas in China. So how to identify grape white rot? What are the prevention and control techniques?

First, how to identify grape white rot?

1. Ear disease

It often causes a large number of ears to rot, and the ears near the ground are prone to disease. the damaged ears are generally water-immersed, light brown and irregular spots, showing rotting shape. one week after the disease, there is a dense layer of grayish-white particles on the fruit face. the diseased part gradually dries and shrinks and spreads to the fruit grains, and the pedicel changes to light brown at first, then expands gradually and becomes soft rot, and then the whole grain turns brown and rotten, but the shape of the fruit remains unchanged. Ear rachis and fruit stalks are often dried and constricted, and when serious, it causes whole ear rot. The diseased fruit hanging on the tree gradually shrinks and dries up into a stiff fruit with obvious edges and corners. The disease occurs before the fruit is starched, the sugar content of the diseased fruit is very low, it is easy to lose water and dry up, and the dark brown stiff fruit is often hung on the tree for a long time, which is easy to be confused with room blight; it is susceptible to disease after sizing, and the diseased fruit is not easy to dry up and fall off when it is shaken.

2. Branch and vine disease

In the damaged places, the coring places of new shoots and postharvest stalks, especially the sprouting tillers germinated from the soil, the disease is most likely to occur. At the beginning of the disease, the disease spot showed a light yellow water immersion, the edge was dark brown, with the growth of the branches, the disease spot also expanded to the upper and lower ends, became brown and sunken, and the surface was densely covered with gray-white particles. Then the epidermis turns brown, warps up, and the diseased cortex is separated from the woody part, often splitting longitudinally into hemp. When the diseased vine surrounds the vine, it constricts in the middle, and sometimes becomes thicker or nodular at the junction of the disease and health at the upper end of the spot due to the obstruction of nutrient transport.

3. Leaf disease

Most of them occurred at the leaf edge, leaf tip or damaged place, initially showing light brown, water-immersed disease spot, gradually spread to the middle of the leaf, and formed no obvious concentric wheel pattern, and the disease spot was easily broken after drying up. When the weather is wet, white dots (conidia) are formed, which are mostly distributed near the leaf veins.

The most important feature of the disease is that there is a special mildew smell in the damaged part when it is moist.

What are the prevention and control techniques of grape white rot?

1. Select disease-resistant varieties

According to local conditions, disease-resistant varieties, such as rose incense and longan varieties, are more resistant to white rot.

2. Do a good job in clearing the garden

Do a good job in clearing the garden and reduce the source of primary infection. Timely removal of diseased fruit, diseased vine, diseased leaf and other diseased tissue. Clean up the dead branches and leaves on the ground, burn them or bury them deeply, and reduce the source of infection. Do a good job of drainage, reduce the humidity in the garden, reduce unnecessary wounds as far as possible, and reduce the chance of bacterial infection. After falling flowers, cover both sides of the grape plant with plastic film to prevent the spread of germs in the soil and reduce the chance of infection.

3. Chemical control

Soil disinfection, the seriously sick orchard should be evenly mixed with 50% thiram powder, sulfur powder and lime powder according to the proportion of 1:1:2, and then sprinkled on the vineyard ground, sprinkling 1kg per mu, or 200x pentachlorophenol sodium spraying the ground, can reduce the disease.

After the grape is unearthed, the grape is first sprayed with 3-degree stone-sulfur mixture once, and Bordeaux liquid is sprayed before flowering.

When the grape sprouted 3-5 leaves, it began to combine the prevention and control of other diseases, spraying once every 7 ~ 10 days, especially after rain, spraying 10% difenoconazole water dispersible granule 2000 × 3000 times, or 50% carbendazim wettable powder 600 times, 70% carbendazim wettable powder 700 times, or 80% mancozeb 800 times. When the growth of fruit is basically stopped, azole pesticides such as nitrile, flusilazole, propiconazole, uniconazole and so on can be used. It should be rationally matched and used in rotation with 1V 0.7 Bordeaux liquid fungicide.

Warm reminder:

Grape white rot can occur in the growing season, there are a large number of pathogens in the vineyard, as long as the humidity can be satisfied, it can be infected through the wound. Therefore, from spring to autumn, it is a key period to control grape white rot. The storm and hail caused a large number of grape wounds and the humidity needed for grape white rot infection, which provided better conditions for the incidence of grape white rot.

The occurrence of white rot is directly related to the rainfall and rainfall from May to June. Therefore, after each rainfall (more than 5 mm), spray therapeutic fungicides in time, and then spray fungicides at certain intervals.

In case of storm and hail and weather damage to grapes, spray fungicides in time for prevention and control. The incubation period after white rot infection in summer is generally 5-6 days. Therefore, prevention and treatment must be carried out before the end of the incubation period.