What are the symptoms of downy mildew in cabbage? How to carry out scientific prevention and control

Brown spots or sunken spots appear on the cotyledons of downy mildew of cabbage, yellow polygonal lesions appear on the true leaves, and white mold layers appear on the back of the leaves and on the stem of the seedlings when wet. When the disease is severe, the cotyledons and young stems dry up and die. Apply foot fertilizer, timely top dressing and foliar fertilizer spraying, avoid partial application of nitrogen fertilizer, and improve plant disease resistance; Moderate watering, flood irrigation and noon watering on sunny days, water is indispensable after wrapping the heart; Diseased plants were uprooted in time in the field, and diseased residues were removed after harvest to reduce re-infection during the cellar period.

Downy mildew of cabbage generally occurs first in the outer leaves and gradually expands to the inner layer. From sporadic onset to field-wide common onset, leaf onset presents yellow spots on the front of the leaf and produces hoarfrost mildew on the back, that is, the sporangia of the pathogen. When the disease is severe, the mold layer covers the entire leaf, and finally the diseased part is yellow-brown to dark brown and withers and dies. The disease of the remaining seed plant, the leaf symptoms are the same as that of the adult plant, the flowers, peduncles, and seed pods are deformed and swollen, twisted like a dragon head, and there is a white frosty mold layer on the surface, and there are few or no seeds.

The affected part of the stem and peduncle also showed white sparse mold layer symptoms.

Scientific prevention and control can implement high and narrow furrow deep furrow cultivation, sowing at the appropriate time, reasonable dense planting, and preventing field canopy; Apply foot fertilizer, timely top dressing and foliar fertilizer spraying, avoid partial application of nitrogen fertilizer, and improve plant disease resistance; Moderate watering, flood irrigation and noon watering on sunny days, water is indispensable after wrapping the heart; In the field, the diseased plants were uprooted in time, and the diseased residues were removed after harvest, so as to reduce the symptoms of re-infection at the seedling stage at the cellar stage At the beginning of the disease, there was a white frosty mold layer on the back of the leaves, and there were no obvious symptoms on the front of the leaves.

Downy mildew refers to the plant disease caused by downy mildew in the fungus, downy mildew is an obligate parasite, and a very small number of downy mildew can be artificially cultivated, such as the grassy finger fungus that causes millet white disease, and the parasitic downy mildew that causes downy mildew of cabbage. It is easy to be complicated by horn spot disease, and when the air is humid, a frosty mold layer is formed on the back of the leaf, which can sometimes spread to the leaf surface. In the later stage, the lesions die and die, yellowish-brown, and in severe cases, all the outer leaves wither and die, similar to Verticillium wilt.

White mold will appear on the back of the cabbage stalk at the larval stage of downy mildew of cabbage, and the mold will turn yellow-brown at the adult stage and spread to the stem and leaf part, and the leaves will turn yellow and rot. Prevention of cabbage downy mildew should start from seed selection, select insects that are resistant to diseases and insects, and do a good job of soaking seeds before sowing to prevent pests and diseases.

Downy mildew of cabbage is manifested by dry rotten leaves and black roots. Scientific control methods can use green vegetable plants before the maturity of grass and wood ash ditch ridge vegetables, and can also use Hu Nandan to sprinkle in the soil of the roots of vegetable plants.

The first point is the symptoms, which is that there are a lot of white dots on it, the second point is that there are a lot of black dots on it, and the third point is that there are a lot of bugs that are scary.

For green vegetables with young stems and leaves as edible organs, once infected with downy mildew, it will seriously affect the normal growth of green vegetables, resulting in poor quality and yield decline, so in the production, it is necessary to strengthen prevention, focus on prevention, and find that the diseased plants are uprooted and disinfected in time to avoid spreading infection. In order to better do a good job in the prevention and control of downy mildew in green vegetables, we must first understand the pathogenesis and symptoms of downy mildew in green vegetables, so as to provide a technical basis for further accurate prevention and development.

<> downy mildew is a fungal disease, caused by false downy mildew infiltration, its occurrence conditions are water droplets or water film on the leaves to germinate, rainy and humid environment is conducive to the germination and invasion of downy mildew, and the disease is serious, even rainy or foggy weather, the disease will spread rapidly, while low-lying, planting too dense ventilation, lack of fertilizer is also easy to induce downy mildew.

The above is about the occurrence of downy mildew, symptoms and prevention methods, but in general, downy mildew should be prevented and difficult to treat, so in production, it is mainly necessary to prevent it, supplemented by prevention, and find that the diseased plant is pulled out in time, and comprehensive prevention can effectively control and reduce the infection of downy mildew on greens.

How to remedy downy mildew in greens. After downy mildew occurs in green vegetables, it is recommended to remove the diseased seedlings in time, take them out of the field to burn or bury them deeply, and spray them in time to prevent and control them. The agent can choose 235-470 grams of 40% aluminum triethylphosphonate wettable powder, or 560 grams of azitoxybacterium chlorothalonil suspension 80-120 ml mu, or 80% mancozeb wettable powder 150-225 grams of mu, or 28-36 grams of oxantone frost urea cyanide water dispersible granules, or 15-20 grams of 80% azoxystrobin water dispersible granules, the above drugs once for 7-10 days, 2-3 times in a row, pay attention to the alternate use of drugs.

Leaf litter caused by blight is the main disease of greens in protected areas. The affected part is water-stained, the leaves and flower sprouts are dark green, and the roots and bulbs are light brown, and the diseased parts have no obvious edges. When wet, the diseased part produces white and sparse mold, and when dry, the diseased leaves turn yellow.

It will cause the leaves of the cabbage to turn yellow, and it will also lead to a significant decrease in yield, and it will also cause the leaves of the cabbage to dry up.

The yield will be reduced a lot, and the bok choy has some black spots and is not evenly distributed, etc., these are all symptoms of downy mildew in bok choy.

At the beginning of the disease, small spots appear on the leaves of small cabbage, and then gradually turn to yellow-brown, in the corresponding position on the back of the leaves of the diseased spots, there will be a white mold layer, and in severe cases, the lesion site will appear hypertrophied and curved deformity, and the peduncle will be infected, showing black-brown necrotic spots, resulting in hollow or semi-solid pods.

Commonly known as white mold, frost leaf disease, etc., it is a common fungal disease in the planting process, which occurs very commonly and the harm is more serious. In addition to the harm to Chinese cabbage, radishes, cabbage, cabbage and other vegetables are also very serious. For the Chinese cabbage in the open field autumn, the downy mildew fungus in the cabbage field is mainly spread through the airflow, germinating and invading the cabbage under the condition that there are water droplets or water film on the leaves, and the rainy and humid environment is conducive to the germination and invasion of the pathogen, when the temperature is low, the rainfall or fog is heavy, the disease will spread rapidly, and the terrain is low-lying at the same time.

If it is an adult cabbage stage, it is generally the outer layer of cabbage leaves that begins to disease, and slowly expands to the inner layer of cabbage leaves, from the gradual onset to the general appearance of disease, and the leaves will appear light yellow small spots when they occur, and in severe cases, there will be a white mold layer, that is, the sporangia of the pathogen. Choose excellent varieties with disease resistance, select disease-free seeds for seed retention, and can also use Fumei double or methacryl with seed weight before sowing for seed dressing.

Increasing phosphorus and potassium fertilizer during top dressing can improve the disease resistance of Chinese cabbage plants, and can also ensure the nutrition of Chinese cabbage during the growth period and enhance disease resistance. When planting, high furrow seeding is advocated, which is conducive to drainage, prevents waterlogging and reduces humidity, which can also reduce the occurrence of downy mildew and soft rot. Remove and kill downy mildew eggs, sporangia, reasonable fertilization, proper dense planting, dry watering, waterlogging and drainage, keep the soil moisture uniform, and provide a good growth environment for Dabaiqin, you will be able to achieve high yield.

It is more necessary to have sufficient fertilizer and water in time to promote the number of leaves, the growth quantity and quality. Therefore, in addition to applying the base fertilizer that is sufficient for the farmer's fertilizer, nitrogen fertilizer is also applied at the seedling stage according to the growth of the seedlings, so that the thin fertilizer is applied frequently. At the same time, phosphorus, potassium fertilizer and foliar fertilizer should be supplemented in time in the later stage.

Some have already formed balls and are strong. At this time, carbendazim is used for prevention and control, and after ten days to half a month, the second control will be carried out, and the downy mildew of this Chinese cabbage will not appear, and it can be completely controlled, including insect pests.

Chinese cabbage downy mildew can be sprayed immediately at the beginning of the disease or when the central diseased plant is found. Spraying must be meticulous and thoughtful, especially on the back of old leaves. The weather is dry after spraying and does not need to be sprayed.

1.There were significant differences in the incidence of disease-resistant varieties. Chinese cabbage varieties resistant to viral diseases are generally also resistant to downy mildew and can be selected according to local conditions.

2.The appropriate sowing date should be determined according to the stubble, variety and climate. Early sowing is serious, late sowing is mild, but the heart is insufficient, but in case of high temperature and drought years, Chinese cabbage should be sown late, the disease resistance of hybrids is stronger than that of farmer seeds, and the sowing date can be arranged in front.

(1) Seed control: soak in 50 degrees warm water for 20 minutes before sowing, dry after fishing, or soak with 200 times the amount of 50% ammonium substitute solution for 15 minutes, wash and dry and sow seeds, which is the most effective way to prevent disease.

2) Management and control: cultivation in high and narrow deep furrows, reasonable dense planting, application of basic fertilizer, increase of phosphorus and potassium fertilizer, timely supplementation of fertilizer, timely spraying of foliar fertilizer.

3) Fertilizer management: avoid heavy irrigation, after rain or after watering, timely tillage of the soil, timely application of nitrogen fertilizer and potassium fertilizer.

Pesticides should be used, because pesticides treat this pest and disease very well, and after they are used up, they can make the yield high.

Pesticides. Because after my cabbage is sprayed with pesticides, downy mildew is not allowed, so pesticides can be used to prevent and control it.

Downy mildew is one of the most widespread and harmful diseases of cabbage vegetables.

Symptoms and their identification: Downy mildew can infect and harm Chinese cabbage at all growth stages. Xiao Miao was killed:

In the early stage, a white mold layer is produced on the back of the leaf, and there are no obvious symptoms on the front of the leaf, and the stem and leaf are yellow and dead in severe cases. Adult plant damage: white mold appears on the back of the leaf, pale green lesions appear on the front of the leaf, and gradually turn yellow or yellow-brown, and finally dry up.

Since the expansion of the lesion is limited by the leaf veins, the lesions are formed in the mesophyll between the leaf veins, which are polygonal. After the heart-to-heart period of Chinese cabbage, the disease develops rapidly, and a large number of dead spots are connected into patches, and the bulbs are damaged in severe cases, which affects the quality of products.

Prevention and control methods: choose disease-resistant varieties. Seed sterilization.

In order to prevent seeds from carrying bacteria, 50% Fumei double wettable powder or 75% chlorothalonil wettable powder and 35% methaloxin can be used to mix seeds according to 4% of the seed amount. Reasonable crop rotation and timely sowing. Pharmaceutical prevention and control.

Generally, spraying is started when the central disease plant appears in the early stage of the disease, and timely prevention before the onset of the disease is more effective. In the production of Chinese cabbage, spraying should be done before sealing the ridge, generally every 5 7 days, and spraying more than 2 times in a row. Commonly used agents are:

40% ethylphosphine aluminum wettable powder 250 300 times liquid, 25% methalonil wettable powder 800 times liquid, 75% chlorothalonil wettable powder 600 times liquid, 40% synergistic methaloxin 800 times liquid, Pulik water solution 600 times liquid.

At the beginning of the disease, small spots appear on the leaves of bok choy, and then gradually turn yellowish-brown. There is a white mold layer on the back of the diseased leaves. In severe cases, the lesion site appears as a swollen and curved deformity of fat, pedicle infection, dark brown necrotic spots, and the formation of empty or semi-solid pods.

irregular lumpy yellow-brown blight spots on the leaf surface; The corresponding sparse white mold symptoms (sporangia and sporangia) appear on the dorsal surface of the leaves, and in severe cases, the lesions are combined into plaques of different sizes, causing the leaves to dry up.

At the beginning of the disease, small spots appear on the leaves of small cabbage, and then gradually turn to yellow-brown, in the corresponding position on the back of the leaves of the diseased spots, there will be a white mold layer, and in severe cases, the lesion site will appear hypertrophied and curved deformity, and the peduncle will be infected, showing black-brown necrotic spots, resulting in hollow or semi-solid pods.

Pesticides. Because the cabbage I grow at home is cured of downy mildew after being sprayed with pesticides, so pesticides should be used to prevent and control it.

It can be controlled with pesticides. Some medications can prevent downy mildew in bok choy.

No matter what kind of pests and diseases, as long as the corresponding pesticides are sprayed, they can be solved. Because if it's serious, they are very afraid of pesticides.

Brown spots appear on the cotyledons, or sunken spots, yellow polygonal lesions on the true leaves, and white mold layers appear on the dorsal and seedling stems when wet. When the disease is severe, the cotyledons and young stems dry up and die. If it is found that there are rotten white spots on the cabbage, it means that the cabbage is basically downy mildew, which is currently not a good method, because it is found that the downy mildew cabbage has basically been formed, and the best way is to prevent it in the early stage.

The water-stained green spots with unclear edges at the beginning of leaf infection, the later lesions expand, and the polygonal yellow-brown lesions are limited by the leaf veins, and the back of the leaves is white and sparse mold layer, and the mold layer is more obvious when the humidity is high, which is the symptom of the disease, and the adult plant stage is damaged, and the outer leaves generally develop the disease first and gradually expand to the inner layer; It ranges from sporadic onset to field-wide common onset. The leaf disease presents a yellow spot on the front of the leaf and produces a white frost mildew on the back side, that is, the sporangia of the pathogen.

Chinese cabbage downy mildew is commonly known as white mold, frosty leaf disease, etc. In addition to harming Chinese cabbage, it can also harm other cruciferous vegetables such as radish, mustard, rape, bok choy, cabbage, cauliflower, etc. In particular, the northern Chinese cabbage was the most affected.

It can occur from the seedling stage to the core stage, and the disease is more serious after the rosette stage, mainly harming the leaves, stems and peduncles. Seed pods can also be damaged. Downy mildew refers to a plant disease caused by downy mildew in the fungus.

Downy mildew is an obligate parasite, and a very small number of downy mildew can be artificially cultivated, such as Posa digitaria which causes millet white disease, and parasitic downy mildew that causes downy mildew of cabbage.

Chinese cabbage downy mildew occurs in all parts of China, and it mainly harms Chinese cabbage in Northeast, North China and Northwest China, and the loss can reach 50% to 60% in epidemic years, which is one of the important diseases in Chinese cabbage production. On the back of the leaf, there is a white sparse mold layer, and the mold layer is more obvious when the humidity is high, which is the symptom of the disease (pathogen sporangia and sporangia). As the disease progresses, the polygonal plaques often form large patches, eventually causing the leaves to turn brown and dry up.