The yellow leaf disease of Chinese cabbage harms the foliage, how to prevent and control the yellow

1.Potassium and magnesium deficiency in Chinese cabbage can lead to yellowing of leaves. Since these two mineral elements have strong fluidity in the plant, in the case of short supply, Chinese cabbage will transfer potassium and magnesium from old leaves to new leaves through its own regulation.

Therefore, leaf yellowing caused by potassium and magnesium insufficiency first appears on the old leaves, that is, on the leaves around the Chinese cabbage. The specific manifestations of the two elemental deficiencies are different. The leaves of potassium-deficient cabbage are yellow with gold rims, and gradually expand to the center of the leaves with the increase of nutrient deficiency. Leaf yellowing caused by magnesium deficiency mainly occurs between mesophyll veins.

The key to avoiding potassium and magnesium deficiency in Chinese cabbage is to apply sufficient basal fertilizer to ensure the continuity of nutrients**. Magnesium fertilizer is mainly supplemented with organic fertilizer and calcium, magnesium and phosphorus fertilizer, but Chinese cabbage needs potassium fertilizer, so in addition to basal fertilizer, top dressing should also be carried out at the beginning of grain filling. If elemental deficiencies are already present, foliar fertilizer spraying is a faster way to supplement.

2.There are three kinds of leaf yellowing caused by improper fertilization: one is that the applied organic fertilizer is not completely decomposed, and the ammonia and heat released in the soil will destroy the root system of Chinese cabbage, resulting in poor root development and insufficient absorption of mineral elements and water.

Obstacles can cause yellowing of leaves; Secondly, if the amount of chemical fertilizer is too large or the application is not uniform enough, and the contact with the chemical fertilizer with too large concentration, the root system will be damaged and the leaves will turn yellow; Third, the content of effective nutrients in the soil that can be absorbed by the roots of Chinese cabbage is insufficient, resulting in malnutrition of Chinese cabbage and yellowing of leaves. The amount of fertilizer is not exceeded, and spreading evenly is an important measure to avoid burning seedlings and causing yellow leaves. In order to avoid the yellowing of cabbage leaves caused by improper release, it is necessary to ensure that the applied organic fertilizer is fully fermented and decomposed; Secondly, the organic fertilizer should be evenly sprinkled, and a small amount of top dressing should be applied in batches to avoid burning the root system if it is too concentrated or too close to the root system; Third, the soil must be kept loose, breathable and with a suitable moisture content to ensure good growth of the root system and the effective use of nutrients in the soil around the root system**.

3.In natural saline-alkali soil or secondary salinized vegetable land, soil salinization caused by excessive application of chemical fertilizer and improper application of organic fertilizer will also lead to yellowing of Chinese cabbage leaves, because in the soil with too high salt content, the root system will produce salt stress, which makes it difficult for the root system to stretch and bind, weaken its absorption capacity, and make the nutrients and water required for the production and growth of Chinese cabbage unable to be effectively supplied. The high multiple cropping index of vegetable land in China, and the long-term blind application of excessive chemical fertilizer to pursue high yield, resulting in a large amount of mineral salt in the soil not being absorbed and utilized, is the main reason for the secondary salinization of the soil.

In order to avoid yellowing of Chinese cabbage due to high salt content, and to avoid saline-alkali soil when selecting a site, fertilization must be tailored to soil fertility and fertilizer requirements. When choosing organic fertilizer, the use of commercial organic fertilizer should be avoided as much as possible, and the farmhouse fertilizer that is completely decomposed should be chosen. 4.

The water content is too high, the root system of Chinese cabbage is small, and the absorption capacity is weak, but the ground leaf area is large, and the water evaporation loss ability through transpiration is strong. In order to ensure the good growth of Chinese cabbage, a high soil moisture content is required to improve the water absorption efficiency of the root system. However, when the soil moisture content.

This disease is usually caused by fungal infection, and carbendazim solution can be tried to prevent it.

The yellow leaf disease of Chinese cabbage harms the foliage, how to prevent and control the yellow leaf disease of Chinese cabbage? The first method is agricultural prevention and control, the selection of disease-resistant varieties; Sowing should avoid the hot and dry season; Squatting seedlings should be moderate to prevent soil drought at the seedling stage and ensure the normal development of the root system. The second should be the prevention and control of pesticides, irrigating roots with pesticides, you can choose 40% polysulfur suspension 600 700 times liquid, or 50% thiophanate-methyl wettable powder 500 times liquid, 50% mixed sulfur suspension 500 times liquid, 50% benmonyl wettable powder 1500 times liquid, synergistic carbendazim wettable powder 200 300 times liquid, etc., every 10 days or so for prevention and control, even prevention 1 2 times.

Pesticides. Because after my cabbage was sprayed with pesticides, the yellow leaf disease disappeared, so pesticides should be used to prevent and control it.

For example, if you buy a bag of cabbage or more than one bag of cabbage seeds the year before the big year, and there is no electricity to plant it, then you will leave this bag of seeds for this year or next year, then it will be easy to have Verticillium wilt; In the early stage of the disease, the leaves of cabbage will appear to fade on the surface, and there is no obvious demarcation. And on the back of the white spots are produced, and then as the disease worsens, the spots continue to expand and extend, and gradually merge together to form patches of inappropriate size. A white powder appears on the plaque.

Chinese cabbage has high requirements for soil, and at the same time of pulling seedlings and clearing the garden in time for the previous crops, if the waterlogging and disease occurrence occur at the end of the previous crops, lime and fungal agents should be used for soil disinfection; If the secondary salinization of the soil in the shed is serious, apply enough fully decomposed organic fertilizer, nitrogen, phosphorus, potassium fertilizer with application, fertilize to avoid burning the root system, cultivate the loose soil diligently, improve soil aeration, promote root development, and drain water in time after rain, and completely remove the disease residues in the field after harvesting.

To prevent the occurrence of such diseases, we should do a good job in seed disinfection and root soil disinfection to ensure that there are no pathogenic bacteria in the soil or effectively prevent pathogenic bacteria from invading the plant. If the diseased strain has been found, then as the disease worsens, the spots continue to expand and extend, and gradually merge together to form patches of inappropriate size. White powder appears on the plaque, and in severe cases, all the diseased leaves of the cabbage are covered, causing the leaves to lose nutrients and gradually die and fall.

To prevent the occurrence of such diseases, we should do a good job in seed disinfection and root soil disinfection to ensure that there are no pathogenic bacteria in the soil or effectively prevent pathogenic bacteria from invading the plant. If the diseased plant has been found, there are many high temperatures, rainy weather, insufficient light, poor seedling resistance, and off-season cultivated plants are susceptible to diseases. It can be seen from its disease conditions that it is also very important to clean up the field after this stubble of cabbage, so as to avoid pathogenic bacteria from infecting the next crop.

Pesticides. Because my cabbage was treated with pesticides, the yellow leaf disease was cured, so pesticides should be used to prevent and control it.

selection of disease-resistant varieties for agricultural measures; Sowing should avoid the hot and dry season; Squatting seedlings should be moderate to prevent soil drought at the seedling stage and ensure the normal development of the root system. For root irrigation, you can choose 600 700 times of 40% polysulfur suspension, or 50% thiophanate-methyl wettable powder 500 times, 50% mixed sulfur suspension 500 times, 50% benbenazim wettable powder 1500 times, and 200 300 times of synergistic carbendazim wettable powder, etc., every 10 days or so, once in a hundred days or so, even 1 2 times.

Strengthen field management. Squatting seedlings moderately, change the habit of squatting "full moon", prevent soil drought at the seedling stage, and water and cool down frequently in case of high ground temperature in dry years at the seedling stage to ensure the normal development of the root system.

I think that Chinese cabbage yellow leaf disease is a disease that mainly harms the foliage, if we want to better prevent and control this disease, we should take corresponding measures in advance and spray the ** medicine on the surface of Chinese cabbage.

Agricultural control, the selection of heat-resistant and disease-resistant varieties, such as 87 114, Jiaobai No. 8 and other varieties; Choose a plot with a recreation period of at least 1 month and make the ground level; In case of dry weather, watering and cooling should be carried out decisively at the seedling stage to prevent root injury and eliminate the channel of pathogenic bacteria invasion.

Pesticides. Because my Chinese cabbage is sprayed with pesticides every year, and the leaves have never yellowed, I should use pesticides to control them.

After the harvest of vegetables or other crops in the previous season, the garden was not cleaned well, so there were more pathogens in the vegetable garden, which led to the occurrence of this disease; The density of cabbage planting is too dense, and the ventilation and light transmission are not very good, and over time the phenomenon of Verticillium wilt appears.

Sandy loam and loam soils are most suitable, and they should be close to water sources for easy irrigation. Apply 1000 1500 kg of fully decomposed manure and compost or 45 75 kg of special fertilizer for vegetables per mu, and make ridges to make furrows after land preparation, and furrows are wide and meter. After the previous greenhouse cultivation, do not dismantle the shed, leave the top film, remove the skirt film, the pathogen of cabbage blight overwinters in the soil, and the ground temperature is higher than 10 when it enters the saprophytic stage, and the pathogenic bacteria are scattered from the roots, and can also spread through rain, irrigation water, fertilizer or seed spread.

Pathogenic bacteria can infect plants under the condition of soil temperature of 11-30 and soil moisture of 20%-60%.

At the same time, the residue of pesticides on vegetables is reduced. In addition to pesticide control, reasonable fertilization is also very important, especially the increase of phosphorus and potassium fertilizer can effectively improve the disease resistance of crops and reduce the chance of disease. : Timely topping, timely removal of ineffective flower buds, pruning of ineffective branches and leaves, etc., can reduce premature aging and promote yield increase to a certain extent.

Apply organic fertilizer and biological fertilizer, apply fully decomposed organic fertilizer, reduce the single concentrated and large use of chemical fertilizer, and appropriately increase phosphorus and potassium fertilizer. New soil seedling or bed soil disinfection, mix well with 50% carbendazim wettable powder 5 6 kg of soil per mu, first sprinkle 1 3 medicinal soil on the furrow surface, and then sow it, and then cover it on the seeds with medicinal soil.

After the seedlings are fixed or planted, the growth is slow, and half of the leaves fade green, resulting in half or the whole leaf wilting, as if lacking water, pulling up diseased plants, few fibrous roots, cutting the main stem, and turning brown in vascular bundles. After the diseased strain is found, fungal fungicides should be used in time, such as 70% methyl tobuzine wettable powder or 64% alum.

There were no obvious symptoms on the leaves of the seedlings of Chinese cabbage yellow leaf disease, and the pathogen was infected by the root system at the 2 4 leaf stage, and the vascular bundle of the main root system turned brown and turned black after growing to the core stage. At the rosette stage, the leaves suddenly show symptoms of water deficiency, wilt during the day and recover at night, and the leaf veins turn brown at the centering stage, and the whole leaves shrink and curl inward due to water loss, which eventually leads to yellowing or death of the whole plant. The cabbage that forms the commodity value is harvested with shrunken leaves and reduced weight per plant, incomplete taproot system and brownish-black vascular bundles, and shortened storage time.

Chinese cabbage yellow leaf disease affects the growth of Chinese cabbage, the symptoms of Chinese cabbage yellow leaf disease are that at least half of the leaves are green and begin to degenerate, the whole leaf is wilted, it looks like a lack of water, and the diseased plant has few fibrous roots, and the vascular bundles turn brown.

The condition of Chinese cabbage yellow leaf disease is that the leaves of Chinese cabbage turn yellow and the yield is reduced, which is caused by the affected photosynthesis.

The nutrients in the soil are not well absorbed and utilized by crops. At this time, the cabbage leaves appear yellow due to the lack of fertilizer**. Therefore, in the dry and rainy weather, it is necessary to water in time to meet the needs of the normal growth of cabbage.

Use test strips to measure the pH value of the land to determine whether to water some weakly acidic rainwater or rice water to change the acidity value of the vegetable field, reasonable watering, scientific fertilization, and pay attention to the soil environment, you can avoid most of the yellowing problems.

The periphery is a pale yellow halo, and the periphery of the lesion on the back of the leaf is dark green. When the air is humid, a light gray mold is produced on the lesions on the back, that is, the conidia and conidia of the pathogen. In the later stages, the lesions become white and translucent, and finally rupture and perforate.

There are three reasons for the yellowing of cabbage leaves, one is not watered in time, the second fertilizer is not reasonably fertilized, and the third is that some areas have too much reduction, and it is necessary to use two percent of sulfuric acid to water in order for cabbage to grow vigorously. 1. There are many aphids, most of which are caused by sucking behind the leaves. 2. Lack of fertilizer.

Cabbage grows vigorously and needs to be topdressed frequently, otherwise the leaves are yellow. 3. Poor ventilation, too dense, stuffy. It prefers cooler climates.

Too high a concentration of fertilizer can cause problems with its absorption, which can lead to calcium deficiency. When the weather is dry, there is no timely watering, especially during the rosette stage, the lack of water will lead to a decrease in the fertilizer absorption capacity of the roots, resulting in a lack of nutrients in the cabbage, resulting in dry leaves. Natural conditions.

1) Do not plant cabbage in low-lying places and soak it in water frequently. (2) Crops are planted in rotation to avoid virus invasion. (3) Go to the agricultural station to select high-yield Chinese cabbage seeds.

For example, Shandong cabbage is famous all over the country. Do not keep the seeds for yourself.

In the later stage, the yellow spots form irregular yellow leaf spots, and if the ground is more humid, the back of the leaves will also grow gray-white mildew, so that the cabbage leaves turn yellow and dry from the outside to the inside, and only the part of the cabbage sum is left in serious cases. When we transplant cabbage seedlings, we must water enough on the first day and cut them into mounds for transplanting on the second day, so as to avoid damaging the roots and shorten the slow seedling period of cabbage.

First of all, the fibrous roots of cabbage will be fewer, and the vascular bundles will change from green to brown; The second is that the leaves will fade from the edges, turn yellow, and look like wilting.

The leaves of the plant will be yellow, and will continue to wither, causing the plant to die, affecting the yield of cabbage, and bringing very serious damage to cabbage.