How does turnip downy mildew occur? How to prevent it?

The body of the radish is tormented not only by white powder, but also by the entire cruciferous plant. Fungal diseases in the form of hyphae are generally parasitic on seeds, soil, and bottle posts, and invade vegetables in autumn. Generally speaking, it is most likely to develop in the environment of 16 20, and the disease above 20 is serious, and the disease is aggravated in the rainy season or humid environment, and the onset is often met in autumn, and it is generally spread by wind and rain.

There are many causes of downy mildew, first of all, plant a lot of tree stumps, the number of pathogens in the soil is relatively large, once growing, it may occur for many years, and the variety is also one of them. Fertilization is unscientific. For example, corrosiveness is not good.

Otherwise, only chemical fertilizers are used, and the air permeability of the board is not good after hardening, and it is easy to get sick. When watering, it is easy to replace downy mold if it suddenly dries out and becomes wet or if the density of the planting is too high.

Radish is a vegetable that is often eaten in winter and is very popular, so it is planted to a certain extent in many yards or reclaimed vegetable farms in rural areas, and of course many vegetable farmers are planted and sold in a large area. In the process of growing turnips, pests and diseases are also inevitable. Among them, downy mold is the more difficult species to deal with.

Today, let's take a look at how to prevent the dreaded fungus. Downy mildew on radish is a fungal disease that can occur throughout the growth period of radishes and can cause harm to different parts of radishes.

When the leaves are damaged, irregular spots mainly appear in the early stage of the disease, the moles are light green soaked in water, and white molds appear when the air humidity is high. Then, as the disease worsens, the mole gradually becomes larger, but it is limited by the veins of the leaf, there are many polygons, and the color also changes to yellow or light yellow. When the leaf stem is damaged, black-brown irregular spots appear on the stem, and white mold appears on it.

The disease expands from the lower part of the plant upwards, and as the disease develops, in the later stages, the lesions will wilt and die, and even the outer leaves will wilt and die.

When growing turnips, choose varieties that are resistant to disease and suitable for local conditions. The germs of downy mildew in radish attach to the seeds for the winter, and the seeds with the fungus will directly infect the seedlings, so you should also pay attention to the quality of the seeds when choosing the seeds. Seed treatment should also be carried out before sowing, such as 50% wet powder compound with seed weight, or 75% wet powder white fungus green for seed sterilization.

Reasonable field management, reasonable irrigation fertilizer, deep ploughing in autumn, reasonable regulation of planting density. It is necessary to implement a crop rotation system to prevent the continuous accumulation of diseases. Because radish is a cruciferous crop, in addition to the type and rotation of radishes, it is necessary to avoid continuous cropping with cabbage crops.

The main reason is that there are too many chemical fertilizers to form such a disease, so if you want to prevent it, you should pay attention to the amount of fertilizer you should usually apply, and then there is frequent light, which must be sufficient.

From the leaf to the disease, the front appears amorphous small green spots, with resistant varieties, resistant to viral diseases are generally resistant to downy mildew, different radish varieties have different resistance to downy mildew.

The pathogen invades autumn vegetables after two months of dormancy in the field with oospores. Sow at the right time, apply enough fully decomposed organic fertilizer, and strengthen the prevention and control when there are more diseases in the field, and fungicides or formulas can be used for prevention and control.

In the fall, the vegetables are infested. Generally, it is most likely to develop in an environment of 16-20, and the disease is serious when it is above 20, and the disease will be aggravated in rainy or humid environments, and autumn is just enough to meet the onset of the disease, and generally it will spread with the help of wind and rain. Therefore, many people in rural areas will plant more or less in their yards or small vegetable fields, and of course, there are many vegetable farmers who plant large areas for sale.

In the process of planting radish, pests and diseases are inevitable, among which radish downy mildew is a more difficult one, today let's take a look at how to prevent and control radish downy mildew.

First of all, the radish leaves will be frosty, and then they will wither and curl. Downy mildew first harms the radish leaves, first produces small pale yellow spots, continues to expand into polygonal spots, and produces frost-like white mold on the back of the leaves, and then the leaves will turn black if it is severe. Leaf onset:

At the time of leaf disease, it will start from the base and gradually develop upward, and the leaf surface is scattered with small spots of light green to light yellow, and after the lesions expand, they appear yellow-brown, and appear polygonal spots due to the limitation of leaf veins. When the weather is wet, a layer of white mold will grow on the back of the diseased leaves. When the disease is severe, the lesions will turn purple-black, and the leaves will die from the bottom to the top.

In general, downy mildew does not affect the heart leaves.

Radish downy mildew is also known as "running horse" and so on, it often appears on cruciferous crops, this disease has appeared all over the country, but its incidence is relatively high autumn radish. The onset of downy mildew is not fixed, for example, it occurs at the seedling stage or harvest stage, and it starts with the leaves of radishes, and then the flower stalks and rhizomes.

As well as the occurrence of downy mildew, downy mildew starts from the base of the bottom leaves, and there will be light green or light yellow spots on the leaves of the radish, which will slowly expand into yellow-brown, and white mildew will appear on the back, until the leaves evolve into brownish-purple, which will slowly cause the leaves to wither and the plant to die.

It is recommended to use pesticides, because pesticides can prevent and control downy mildew of radishes, which is very effective.

Pesticides. Because my family has planted dozens of acres of radish, all of which are pesticides, and pesticides will not get downy mildew, so pesticides can be prevented.

It can be prevented by medication. Some pesticides can ** downy mildew of turnips.

Downy mildew is a fungal disease that can occur throughout the growing season of turnips and can damage many parts of turnips. When the leaves are damaged, it is mainly manifested in the early stage of the disease, irregular spots will appear on the leaves, and the spots are pale green and water-immersed. When the air humidity is high, white mold can develop on the spots.

Then, as the disease worsens, the lesions will gradually enlarge, but due to the restriction of the veins, the color is mostly polygonal, yellow, or yellowish. When the stem of the leaf is injured, there will be dark brown irregular spots on the stem, and white mold will also be produced. The disease spreads from the lower part of the plant to the upper part of the plant, and as the disease progresses, it causes the death of the lesions and even the outer leaves.

Reasonable field management, reasonable irrigation and fertilization, deep ploughing in autumn, and reasonable adjustment of planting density for agricultural control. Second, a rotation system should be implemented to avoid the accumulation and aggravation of diseases. Because radish is a cruciferous crop, in addition to rotating with non-radish varieties, it should also be avoided in conjunction with cabbage crops.

Radish should not be sown too early, especially in downy mildew prone areas and drought and water shortage years, and the sowing date should be appropriately delayed for one or two days. There are many causes of downy mildew, the first is to plant a variety of crops, so that there are many pathogens in the soil, and once they grow for many years, they will develop diseases, and varieties are one of them. Fertilization is not scientific, such as bad rot performance, otherwise only chemical fertilizers are used, so that compaction will occur, the air permeability is not very good, and it is easy to get sick.

Reasonable field management, reasonable irrigation and fertilization, deep ploughing in autumn, and reasonable planting density. Second, a rotation system should be implemented to avoid the accumulation and aggravation of diseases. Because radish is a cruciferous crop, in addition to rotating with non-radish varieties, it should also be avoided in conjunction with cabbage crops.

Radish should not be sown too early, especially in downy mildew prone areas and drought and water shortage years, and the sowing date should be appropriately delayed for one or two days. When planting radish, be sure to choose varieties that are resistant to disease and adapted to local conditions. Secondly, it should be noted that the pathogen of radish downy mildew can also attach to the seeds for overwintering, and the seeds carrying the pathogen can directly infect the seedlings, so it is necessary to pay attention to the quality of the seeds when selecting seeds.

We can choose disease-resistant varieties, and virus-resistant radish varieties are generally resistant to downy mildew. Secondly, it is necessary to rotate crops reasonably and sow seeds at the right time. Plots where radish is planted should avoid continuous cropping with cruciferous vegetables; The sowing date of radish should not be too early.

In downy mildew areas and particularly dry years, the sowing date should be appropriately delayed by 1-2 days. The squatting time of radish seedlings should not be too long, and reasonable irrigation and fertilization should be carried out. After the radish is harvested, the countryside should be cleaned up in time and the soil should be turned deep.

Select disease-resistant varieties for seed disinfection: select and plant disease-resistant radish varieties, and in addition, you can leave seeds on disease-free plants, select seeds, and do a good job of seed disinfection.

There will be a lot of mold, and at the same time, the degree of rot will be more severe, and there will also be a lot of diseases, and the leaves will wilt.

It develops from the base to the upper lobe. At the beginning of the disease, light yellow near-round to polygonal lesions are formed on the leaf surface, and a frosty mold layer is formed on the back of the leaf when the air is humid, which can sometimes spread to the leaf surface. In the later stage, the lesions are dead and continuous, yellowish-brown, and in severe cases, all the outer leaves are yellow and die.

The leaves of the radish are particularly yellow, and they are withered and falling, and the radish only blooms and does not bear fruit, and a large piece of it dies.

Radish downy mildew has a distinct central feature, which is characterized by small pale green water-soaked spots on the bottom leaves at the beginning, and then slowly expands into polygonal or irregularly shaped lesions, pale yellow to yellowish brown.

<> symptoms: It can occur from seedling stage to seed harvesting stage, and extends from the lower part of the plant upward. At the beginning of the disease, the leaf surface appears irregular yellowish yellow, and then gradually expands into polygonal or irregular yellow-brown lesions, with a diameter of 3 7 mm, when the humidity is high, white mold grows on the back of the leaf or both sides of the leaf, and the severe lesions cause the leaves to dry up.

The stems are infected with black-brown irregular spots. The root is diseased, and the affected part produces gray-yellow to gray-brown slightly concave marks, which are easy to cause rot when stored. The seed plant is infected, which damages the seed pods, and the diseased part is light brown irregular spots, and white mold grows on it.

Pathogenesis: fungal diseases. The disease occurs mainly in autumn and spring.

The pathogen mainly overwinters and summers on diseased residues, soil, seeds, seed harvested plants or cellar-stored radishes. The temperature is around 16, and the high humidity is conducive to the germination and invasion of pathogenic bacteria. Prevention and control:

selection of disease-resistant varieties; Sowing at the right time, not early; alternate rotation with non-cruciferous crops; Pay attention to remove diseased leaves and plants in the previous stubble. Before seed sowing, mix seeds with 75% chlorothalonil wettable powder or 50% fumeji wettable powder or 25% methamalin wettable powder by seed weight. In the early stage of the disease, the diseased leaves or plants should be removed in time, and 600 times of 75% chlorothalonil wettable powder can be used; 50% sterilized Dan wettable powder 500 times liquid; 25% methamanine wettable powder 800 times liquid; 1500 times of 50% Pythium wettable powder, 1 time every 7 10 days, 3 4 times in a row.

The underside of the leaf should also be sprayed.

Prevention and control points.

Selection of disease-resistant varieties: Choose disease-resistant varieties according to local conditions. Crop rotation:

Severely ill plots are rotated with non-cruciferous vegetables for two years. Cultivation management: advocate deep ditches and high furrows, appropriate density, timely cleaning of ditches to keep drainage and irrigation smooth, apply enough organic fertilizer, appropriately increase phosphorus and potassium fertilizer, and promote the growth of plants.

Autumn Chinese cabbage in Zhejiang and the middle and lower reaches of the Yangtze River is generally sown in late August and early September, and it is better to sow in early autumn in Beijing. Seed treatment: Seed dressing with 40% ethyl phosphorus aluminum wettable powder or 75% chlorothalonil wettable powder by seed weight.

Pharmaceutical prevention and control: in the early stage of the disease, prevention and treatment should be carried out once every 7 10 days, 3 or 4 times in a row; In the year of moderate to moderate to heavy occurrence, 1 time every 5 7 days, 4 6 times in a row, 25% methamanine wettable powder 600 800 times can be used.

FYI! Have fun!

In cold or high altitude areas, the pathogen mainly overwinters in the diseased residue or soil with oospores, or in the remaining plants or on the stored cabbage. In the following year, the oospore germinates to produce a germination tube, which invades from the seedling stem, and the mycelium spreads upward to the first true leaf, and produces sporangia on the young stem and leaf, forming a balanced and limited systematic infection. After the spread of wind and rain, it first infects common cabbage or other cruciferous vegetables; In addition, the pathogen can also attach to the seed for overwintering, sowing the seeds with the fungus directly infect the seedlings, causing the onset of the seedling stage, the pathogen overwinters in the diseased part of the vegetable plant, produces sporangia after overwintering, falls off after the sporangia mature, spreads by air flow, produces a bud tube on the surface of the host, invades by the stomata or from the intercellular space, and produces sporangia in the diseased part after 3 5 days of latent incubation for re-infection, so after many re-infections, until the late autumn and early winter conditions are bad, oospores are produced in the host tissue for overwintering, and after 1 2 months of dormancy, It can also germinate and become the source of infection at the beginning of the next year, warm areas, especially in the areas where various cruciferous vegetables are planted all year round in the south, the pathogen carries out initial infection and re-infection with sporangia and zoospores, causing the disease to start again and again, all year round, and there is no overwintering problem.