Grape downy mildew is the main disease of grapes, what are the characteristics of grape downy mildew

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.

Symptoms of downy mildew in grapes. Grape downy mildew can damage all green tissues of grapes, such as leaves, flower buds, spikes, shoots, tendrils, etc. , and sometimes it can also cause leaf disease.

In general, the leaves suffer the most. The main symptom after the disease is the formation of white downy mildew on the surface of the affected area. When the disease is severe, it often causes a large number of leaves and fruits, and even causes plant death.

Causes of downy mildew in grapes. Internal causes of downy mildew: downy mildew; External causes of downy mildew:

The ambient temperature is high and the relative humidity is high.

Downy mildew patients are the factors: the vineyards are not cleaned in winter and spring, the surrounding vineyards are poorly managed, and there are many pathogenic residues; Prevention is not in place. Prevention and control methods downy mildew control policy:

Prevention first, comprehensive prevention and control. Prevention and control methods of downy mildew: comprehensive control.

Any measures to reduce pathogens, humidity and moisture can reduce the occurrence or probability of downy mildew, including improved drainage systems, landscaping measures and field hygiene (treatment of fallen leaves and diseased tissues) to destroy diseased mycoplasma in a timely manner; Strengthen field management to enhance the potential of the tree. More recently, in combination with expansive fertilizers, humic acid and small molecule carbon have been added to the soil, and decomposing organic fertilizers have been added in the fall.

Medication control. Although agricultural measures are very important and necessary, it is not possible to completely control downy mildew, so the application of chemicals to control downy mildew is unavoidable. Protective fungicides for daily use, such as Formbi, 80% Essence 600-800 times liquid, 42% Spray Fulu 600-800 times liquid, 78% Cobo 600-800 times liquid, 1:

200-240 Bordeaux liquid. Before the onset of the disease, the disease was controlled with 600-700 times mancozeb solution, and at the beginning of the disease, the disease was controlled with 250-300 times 40% megigin solution.

Bordeaux liquid and polymir manganese-zinc wettable powder (methamethyl 10%, mancozeb 48%) are specific drugs for the prevention and control of downy mildew. Effective drugs also include erysipelas, downy mildew, Yikuaijing, Baitai, Jinlei, Kangzheng alum, cough dew, antiviral alum, Yishuang Lingsan, Daknin, methamalin, cobo, propylene zinc, ethylene propylene aluminum, valcard, downy mildewcarb, etherstrobin, cyanide frost urea, copper hydroxide, etc.

After the onset of the disease, a systemic fungicide is used, such as enoylmorpholine, which has excellent system conductivity and is a specific agent for grape downy mildew, but continuous administration is prone to drug resistance.

1. Thoroughly clean the garden in combination with winter pruning, 2. Deep ploughing in autumn and winter, and timely discharge after rain, 3. Strengthen the management of the vineyard, 4. Adjust the indoor temperature and humidity, 5. Spray the agent evenly and thoughtfully.

Physical control: In the growing season and autumn growth and pruning, it is necessary to thoroughly remove diseased branches, diseased leaves and fruits, and prevent them from the roots.

Drug prevention and control: spray a certain amount of Bordeaux solution about ten days before the onset of the disease for protection.

Removal of 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.

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

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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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.

Answer]: The hyphae and spores of downy mildew and powdery mildew are white on grape leaves, so the symptoms of the two diseases are easy to confuse, but the pathogens and pathogenic conditions of grape powdery mildew and downy mildew are obviously different, and the specific analysis is as follows.

1) Symptoms. Downy mildew: It can damage leaves, but also tender parts such as young shoots, flowers, and young fruits; The leaves are diseased, with small amorphous pale yellow water-stained spots appearing at first, and then gradually expanding, showing yellow or brown amorphic lesions on the front of the leaves; A white frosty mold layer is produced on the back of the lesion, which is the sporangia and sporangia of the pathogen; The tender shoots are damaged, and at first they also produce stool deficiency and water-stained lesions, pale yellow, gradually turning yellowish brown to brown, and the surface is also densely covered with white frosty mold; After a young shoot is killed, the growth is stagnant, distorted, and in severe cases, it withers and dies; The young fruit is damaged, the diseased part is sunken, and white mold grows all over it, and it soon shrinks and falls off.

Powdery mildew: damage to the green and tender tissues of grapes such as fruits, leaves, shoots and tendrils, with the fruit suffering the most; When the leaves are damaged, they initially produce small, pale white mildew spots on the leaf surface, and then gradually expand into gray-white powder, and in severe cases, spread to the whole leaf, causing the diseased leaves to shrink and wither; When the fruit is damaged, a powdery mold layer is produced on the fruit surface, and after the mold layer is wiped off, there are brown markings on the fruit surface. Damaged at the young fruit stage, the fruit shrivels and falls off; When the fruit is slightly larger, it is damaged, the epidermal cells die and turn brown, the fruit stops growing, hardens, deformed, sometimes cracks, and the fruit is extremely acidic; In the later stage, the diseased fruit is dried and rotted. The new shoots and fruit stalks are damaged, and the lesions are white at first, then turn brown, and finally turn black, and the surface is covered with a sparse white powder layer.

2) Pathogens. Grape downy mildew is caused by oomycetes and grapes downy mildew infection; Grape powdery mildew is caused by Ascomycetes and B. grape conchotomyceta.

3) Onset conditions. The onset conditions of downy mildew and powdery mildew are significantly different. Downy mildew is suitable for occurrence and epidemic in high humidity and low temperature climatic conditions.

The temperature is about 20 and the humidity is 95%, which is conducive to the occurrence of downy mildew, and the germination and invasion of sporangia and zoospores need to be carried out in the presence of water film. The optimal temperature for the germination of conidia in powdery mildew is 25 30 and the relative humidity is conducive to the occurrence of powdery mildew. On the contrary, the water film is not conducive to the germination of spore piles, and it can also germinate under arid conditions, and the sultry climate is conducive to the occurrence of jujube burning.