Don t know about downy mildew in grapes, what is downy mildew in grapes?

Grape downy mildew is a global disease. China's coastal areas, the Yangtze River basin and North China are widely distributed and have suffered heavy losses. Symptoms:

The leaves begin with yellowish oily spots, white downy mildew on the dorsal surface of the leaves, and then the spots expand into polygonal, yellow to brown spots. Generally, only the leaves are damaged, a large number of early leaves fall off, the branches grow poorly, and the yield is reduced the following year. New shoots, tendrils, florets, and peduncles can produce lesions.

The lesions are oily and yellowish-brown. The diseased flower spikes turn dark brown and rot and fall off. The fruit hardens, droops and shrinks, and white mold grows and falls off.

The pathogen Plasmodium malaria, known as Trichoderma viridis, belongs to the genus Fa Choi. The hyphae spread in the diseased tissues, forming downy mildew, i.e., sporangia and sporangia. The sporangium peduncle is colorless, forming a bunch of 46 peduncles that protrude from the stomata.

The sporangia are colorless, unicellular, oval or oval, with papillae at the apex, with zoospores. The zoospores are kidney-shaped and have two flagella on one side. The oospores produced during the sexual phase are brown, spherical in shape, and thick-walled.

Pathogenic characteristics: Pathogens overwinter in diseased tissues and soil through oospores. It can survive in soil for 2 years.

From spring to mid-June of the following year, oospores germinate to produce sporangia and zoospores, which are spread to the leaves by wind and rain, and invade the leaves through the stomata, and the sporangia can also produce germ tubes to invade directly. The hyphae spread between the leaf cells, absorbing the nutrients in the leaf cells with a conical suction device, and then extending from the sporangia stalk from the stomata to produce sporangia infection, which spread rapidly in the garden. In general, most of the leaves throughout the garden will become sick within 34 weeks.

After autumn, the spores that lay eggs survive the winter. The weather is cold, the rains are early, and the disease is severe many times over the years.

The key to prevention and control is to control the disease at an early stage of onset. Strengthen cultivation and management. After the spring is unearthed, prune the diseased vines and branches, clean up the diseased residues, increase the planting position, increase the application of potassium and phosphorus fertilizers, and pluck the tops and shoot the secondary shoots in time.

Medication protection. After flowering, combined with fruit disease control, spraying is carried out every 1015 days, mainly in the early stage. The agent can be sprayed with Bordeaux liquid, Ludebao suspension, etc.

70% mancozeb wettable powder, 25% methamethyl wettable powder 1000 times, 90% triethylphosphine aluminum wettable powder, or 50% grammethane wettable powder, etc. These drugs are used alternately to reduce drug resistance. Choose disease-resistant varieties.

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Grape downy mildew is a bacterial infection that causes a white layer of frost on the surface of grapes, like a mist of water.

Grape downy mildew is a worldwide grape disease. It is distributed in all grape producing areas in China, especially in rainy and humid areas, and is one of the main grape diseases. When the disease is severe, the leaves are scorched and fall early, the growth of new shoots is poor, the fruit yield is reduced, the quality is deteriorated, and the cold resistance of the plant is poor.

Grape downy mildew is a disease that occurs on grapes caused by unaxial mold infestation of grapes. Grape downy mildew only affects the young tissues of the aboveground part of the grape, such as leaves, shoots, flower spikes and fruits.

Grape downy mildew tends to affect the young tissues of grapes, mainly the leaves, and in severe cases, the inflorescences, fruits and tendrils. At the beginning of the disease, there are pale yellow multicolored patches on the leaf surface, and the back of the leaf has a little white powder, which slowly spreads to the whole back of the leaf with a pale pink layer, and finally turns brown, and the leaf is dry.

<> new shoots and tendrils are injured, translucent water spots appear, yellow-brown sunken lesions appear behind, and a white mold layer also appears at the affected site, and finally stops growing, and in severe cases, it will die. Downy mildew only affects young tissues in the upper part of the grape, such as leaves, shoots, flower spikes and fruits. Leaf infections begin with translucent, yellow-green oil-infested spots with ill-defined margins, which then spread to yellow to brown polygonal lesions, depending on the species or conditions.

When the humidity is high, the lesions heal, and a white mold layer is produced on the back, that is, the pathogen sporangia and sporophytes, and the lesions finally turn brown and the leaves die. The new shoots and tendrils are infected, and at first they are translucent water-soaked lesions, and then they expand into yellow to brown lesions, and there is also a white mold layer on the surface, and the diseased parts are slightly stagnant, deformed or dry. The dew accumulated by the flower spike is infected by bacteria.

Infected flowers and peduncles begin with small oily spots that turn from light green to yellowish-brown. After the onset of the disease, a white mold layer appears, and the diseased flower spikes gradually turn black-brown and rot and fall off.

The stem is damaged by brown necrosis, easy to thresh, wet white powder has white stems, at this time the young fruit is susceptible to downy mildew, the young fruit of hazelnut soft rot appears, the fruit falls off, the fruit surface also has white powder, the damaged fruit stops growing, and the fruit is generally not harmed by downy mildew after ripening. Prevention and control methods, timely topping, weeding, cutting off the lower leaves and new shoots, so that the garden has good ventilation and light conditions, pruning branches and leaves after autumn, and completely picking the fruit out of the garden.

Before flowering and after flowering and late summer and early autumn are the two critical periods for the prevention and control of downy mildew, in these two periods to focus on prevention, the growth period of 10---15 days for a prevention, with 70% Daisen zinc 500 times solution, 75% Dakoning 600 times solution. After the onset of the disease, 25% amicida 1500 times liquid, 68% Jinlei 600 times liquid, as well as fungicides such as quick cleaning and downy mildew carb have a good effect.

This disease affects the plant tissues of the grapes, especially the leaves of the plants, but it also affects the grapes and tendrils, which will have a lot of yellow-brown patches on the grapes at the beginning, and some strange white powdery substances on the back of the leaves, and eventually the leaves will gradually dry up over time.

For example, if the leaves of the grapes are yellowed and die, then the yolk spots appear on the leaves, and white powdery substances will grow on the back of the leaves, and then the yield will decrease, the quality will become worse and worse, and the disease resistance of the plants will become worse and worse.

There are some yellowish lesions on the leaves of the grapes, and there will be some white powder on the back of the leaves, and the leaves will slowly die, which will make the plants grow very small, and in severe cases, they will cause a large area to die.

There will be round, light yellow spots on the front of the leaves, and a white frosty mold layer on the back, which will gradually increase and become connected.

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1. Eliminate the source of the disease. In late autumn, combined with pruning, completely remove diseased branches and leaves, ground residues, fallen leaves, and diseased fruits, and take them out of the garden to be buried or burned.

2. Scientific fertilization. Increase the application of decomposed organic fertilizer and phosphorus and potassium fertilizer to improve disease resistance.

3. Strengthen management. Pruning in time, breaking the secondary shoots in time, topping, and removing the long branches, prevent the branches and leaves from being too densely crowded, so that the branches, leaves, and fruit retention maintain an appropriate proportion. Attention should be paid to ventilation and moisture removal, temperature and light management. In addition, disease-resistant varieties are selected.

4. Spraying protection. Seize the critical moment before the initial infection of the germ, spray Bordeaux liquid, must choose high-quality quicklime and copper sulfate, prepared in the right way, after the first spray, spray once every half month, generally spray 3 to 4 times, you can achieve a good preventive effect. Due to the characteristic of the invasion of pathogens from the stomata on the back of the leaf, the focus of spraying is on the back of the leaf.

This is an effective experience in preventing the occurrence of downy mildew and saving money, especially for the development of pollution-free grapes. This experience is worth learning from.

Introduction: Grapes are the main crops and cash crops in southern China, and the weather in southern China, especially in the southeast coastal area, is the most suitable for planting grapes, and the grapes in Xinjiang are plump and very sweet. In China, grape downy mildew will occur in many grape producing areas, which is the main disease of grapes.

1. Grape downy mildew.

This disease is an ancient bacterium on a global scale, and grape downy mildew, native to the American continent, was first identified in the 19th century. In the middle of the 19th century, there was a grape pest and disease that swept the whole of Europe, we all know that France is the main wine producing area, and his vineyard has not been spared, so they found a life-saving straw, that is, the medicine that can resist the nodoxy grapes, but it is this strong medicine has ***, from the end of the 19th century, grape mildew and downy disease has quietly entered Europe with seedlings and succession. <>

2. Features. The causative agent of downy mildew is a pathogenic fungus called grape downy mildew, which mainly likes to attack the stems and leaves of grapes, and of course, also likes to bully young grape fruits. When it damages leaves, it initially appears on the front of the leaf with irregular water-stained patches with unclear edges, light green to light yellow.

The lesions will also merge with each other to form large spots, and a white frost-like mold layer will appear on the back of the leaves, and in the later stage, the lesions will turn yellow-brown or brown and dry up, and the diseased leaves will generally fall off. <>

Three**. Downy mildew is the same as the mold we know from the public, they all like the characteristics of darkness and humidity, and it rarely occurs in years of high temperature and rainfall, so if the vineyard is low-lying, poor drainage is easy to occur such pests and diseases, the pests and diseases of grapes in Xinjiang are less than those in the southern region, and it is necessary to strengthen the cultivation and management of vineyards, through reasonable pruning, try to remove unnecessary sesame seeds close to the ground is the plant ventilation, reduce air humidity and reduce the chance of virus breeding and infection.

The main characteristic is that the leaves will form irregular lesions, then turn reddish-brown and fall off, and the young shoots will have yellowish water-stained lesions, which may eventually cause the branches to stop growing, and the fruit will appear gray and produce white mold.

It will cause the leaves to die, and it will also make the fruit very poor, and it will die very easily, and it will also greatly affect the yield of the fruit, and it will also make the plant grow poorly.

There are some black spots, and the leaves will be particularly wilted and unevenly distributed, and the yield will be very low, which is characteristic of downy mildew in grapes.

The leaves will wither, various small spots will appear, and white mold will also appear, and the leaves will be very irregular, and at the same time wilt, and so on.

The leaves are damaged, and the leaf surface appears light yellow irregular, oily spots, which are yellow-brown and have inconspicuous polygonal spots after enlargement, and when the environment is humid, the diseased spots produce a layer of white frosty mold on the back of the leaves.

Viticultural techniques.

1. When planting, you should choose a plot with sufficient light and high calories, which is more conducive to the accumulation of sugar.

2. The planting time can be carried out between January and May, and the method is relatively simple. Dig a pit directly on the plot, plant the seedlings in, and water them after planting.

3. Equal growth to a certain height in time to erect a frame, and reasonable fertilization and management. Fertilization can choose safe and hormone-free water-soluble fertile leaf water-soluble fertilizer, which can improve the immune resistance of grapes and reduce the occurrence of diseases.

The prevention and control of grape "downy mildew", first understand what downy mildew is, and then choose drugs!