Onion purple spot disease is very harmful, how to prevent onion purple spot disease?

Pesticide control: The seeds are soaked in 40 formaldehyde 300 times solution for 3 hours, and washed in time after soaking. In the early stage of the disease, spray 75 chlorothalonil wettable powder 600 times, or 64 alum wettable powder 500 times, 70 mancozeb 500 times, 40 big fudans 500 times liquid control methods, purple spot disease on onions mainly harms leaves.

Pedicel. In bulbs, lesions first begin at the tip of the leaf. or form at the site of a wound that thrips hazard.

The initial lesions are small, gray to light brown, **slightly purple, with black mold.

Purple spot disease mainly affects leaves, peduncles, and bulbs on onions. The lesions first occur from the tip of the leaf, or form at the wound of thrips, and the initial lesions are small, gray to light brown, **purple, with black-gray mold. The lesion quickly enlarges into an oval or spindle-shaped prescription 2:

Jingcai (diphenether pyoxystrobin) suspension 20 grams 10% difenoconazole microemulsion 25 grams 70% tofunin (thiophanate-methyl) wettable powder 50 grams Cal Ermei 20 25 grams, or Xingnong Gaimei 30 grams, or Weiwang 35 grams, spray on 15 kg of water.

The continuation extension is brown or dark purple with a yellow halo around it. Dark brown or black-gray mildew with concentric stripes grows on the disease, and the diseased part is softened and easy to break. The incidence of flower peduncle of the seed plant is high, resulting in the shrinkage of the seeds, which can not be fully matured, and the bulb will be damaged before harvest, resulting in erosionStrengthen management, apply more basal fertilizer and top dressing, so that the onion grows robust and enhances disease resistance.

After the onset of the disease, it is necessary to control irrigation to reduce soil moisture and prevent thrips as soon as possible to avoid wounds.

1 bag (5 g) of 75% ditritrixin (oxime tebuconazole) water dispersible granules 70% Antaisheng (zinc propylen) wettable powder 1 bag (25 g), sprayed with 1 nebulizer water whole plant; Before and after rainfall, or before the onset of the disease, you can use 15 20 ml of 43% Cuifu (tebuconazole) suspension, or 25 grams of 10% difenoconazole microemulsion, or 20 grams of Jingcai (phenylether azoxystrobin) suspension, 25 grams of 70% Xiduosheng (propyl zinc) wettable powder, 25 grams of calem 20 25 grams.

Pesticides. Because after the onion is sprayed with pesticides, the purple spot disease is cured, so it can be prevented and controlled by pesticides.

This disease is caused by infection with fungi, and can be prevented and treated with carbendazim solution, which is generally sprayed twice to have obvious effects.

<> symptoms of purple spot disease in shallots.

Shallot purple spot disease is the key to the flower stalk of the leaves and seeds, which is milky white and small at first, and then becomes light brown annular or spindle-shaped slightly dented spot, expands again to dark brown or purple-red, and there is a light yellow halo around it, and the disease department grows dark red or gray-black moldy material with the distribution of the same boat wheel pattern, and the diseased part becomes soft and easy to break. The incidence of flower stalks of seed plants is high, which leads to wrinkled seeds and cannot be perfected. It can also damage the rhizome before it is obtained, causing it to rot.

Onset of shallot purple spot disease.

The source of the disease is the hyphae that spend the winter in the host body or with the disabled body in the soil environment, and in the second year, the conidia are dispersed and spread by cyclones or precipitation, and invade from the vents, wounds or immediately through the outer skin, and the disease is suitable for 24 27, and the disease is not at 12. In warm and humid rainy days, the disease is more serious when there is a lack of fertilizer, drought, weak plant growth and development, or the onion whitefly bites the leaves and causes wounds.

How to prevent and treat shallot purple spot disease.

1. Clean up the pastoral scenery, implement rotation, and prevent continuous cropping of allium vegetables and fruits.

2. Strengthen management, apply more base fertilizer, effective fertilization, and drainage pipes after rain, so that the plants can grow and develop healthily and improve disease resistance.

3. Immediately prevent and control scallion whitefly to prevent the plant from causing wounds, which can be controlled with 1000 times of 50% dimethoate emulsifiable concentrate.

4. Use disease-free seeds, or soak the seeds with 40% indoor formaldehyde 300 times for 3 hours, and clean them immediately after soaking.

5. In the early stage of the disease, spray 500 600 times of 75% mancozeb wettable powder, or 500 times of 58% methalenescozeb wettable powder, 500 times of 64% disinfectant alum wettable powder, or 1500 times of 50% promethane wettable powder, spray 1 time every 7 10 days, a total of 3 4 times.

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Purple spot disease is a common disease of green onions. In July and August this year, there was more rain, high temperature and humidity caused the occurrence of green onion purple spot disease is more common, and more serious, which is the main disease that causes the dry tip of green onion and dead trees, and often causes serious yield reduction. Green onion purple spot disease can also harm shallots, garlic, etc.

The occurrence of purple spot disease in green onions is due to the parasitism of pathogenic bacteria on the body and seedlings of green onions with mycelium, which then causes infection. If you want to control it, you need to apply foot fertilizer, increase phosphorus and potassium fertilizer, strengthen field management, and improve the ability of plants to resist stress and disease.

It is usually infected with the help of airflow rainwater, usually through the stomatal epidermis of green onions. You can choose to plant green onions with strong disease resistance and higher quality.

Purple spot disease is a common disease in green onions. Agricultural personnel strengthened the management of green onions, and selected high-quality green onion varieties with strong disease resistance for sowing; Agricultural personnel should plant green onions in a fertile and loose soil, good drainage and irrigation, and sunny growth environment, which is more conducive to the growth and development of green onions; After the diseased plants are found, agricultural personnel can timely uproot them and take them away from the planting area for destruction, which can prevent the spread of green onion purple spot disease.

What happens to purple spot disease in green onions? How can it be prevented? Green onion purple spot disease is a fungal disease, the fungus overwinters by mycelium or conidia on the diseased residue or seedlings, and is spread by air flow and rainwater, and the pathogen invades through the stomata on the surface of the onion, wound or directly through the epidermis.

The disease is easy to occur under warm and humid conditions, the suitable temperature for the onset is 25 27, less than 12 does not occur, warm and humid disease is serious. Autumn temperatures are just right for germs to multiply. The epidemic of purple spot disease in rain and green onion is accelerating.

Prevention and control measures. 1. Agricultural measures: 1. Select disease-resistant or mildly diseased varieties.

2. Rotation of severely diseased land with non-onion crops. 3. Remove the disease and residue in the field in time and plough deeply after harvesting. 4. The seedling land and planting land should be flat and fertile, and the drainage should be convenient.

5. Implement fitness cultivation, apply sufficient base fertilizer, timely top dressing, nitrogen-based, balanced application of nitrogen, phosphorus and potassium to prevent defertilization in the later stage of growth. Second, the prevention and control of pesticides: after the beginning of autumn, green onions enter the rapid growth period, the occurrence of green onion purple spot disease will seriously affect the growth, so timely spraying, especially after rainfall, spray Fuliku 6ml + Ye Jiamei 20ml + Jiayuan potassium dihydrogen phosphate 40g, once every 7-10 days, spray twice in a row, to promote the rapid growth of green onions.

Clean the garden, implement crop rotation, and avoid continuous cropping of onion and garlic vegetables. Strengthen management, apply sufficient base fertilizer, and drain water in time after rain, so that plants can grow healthily and enhance disease resistance. To prevent and control onion thrips in time and avoid plant damage, you can use 1000 times of 50% dimethoate emulsifiable concentrate for prevention and control.

It can be done with some drugs**, such as carbendazim and tobuzin, which can be used in a fixed proportion and can play a very good role.

Pesticides. Because my onions are sprayed with pesticides every year, and I have almost never had purple spot disease, I should use pesticides.

The lesions are water-stained white dots at first, and then turn into light brown round or spindle-shaped slightly concave spots, continue to expand to brown or dark purple, often with yellow halos around them, and the disease grows dark brown or black-gray moldy matter arranged in the form of concentric rings, and the diseased part continues to expand, causing the whole leaf to turn yellow, die, or break. Onion purple spot disease is mainly caused by leaf and peduncle, which initially appears as water-stained white dots, then becomes light brown round or spindle-shaped slightly depressed spots, and continues to expand into brown and dark purple spots, with a yellow halo around it. The diseased part grows dark brown or black-gray mold with concentric ring-like striated cracks, and the diseased part continues to expand, causing the whole leaf to turn yellow, die, or break.

Purple spot disease is easy to develop under warm and humid conditions, bulb swelling stage is susceptible to disease, sandy soil, dry land, early seedlings, old seedlings, lack of fertilizer, onion growth weak, thrips are serious lesions. When the humidity in the field is high, mold will grow in the diseased part, which is dark brown or black-gray in color, and these molds are arranged in a concentric pattern; When the lesion expands around the leaf, the leaf softens and breaks off from the diseased area. The bulb is mostly diseased in the neck, and the diseased part shrinks, turning pale red or yellow, and mildew also occurs when it is wet.

The disease is characterized by a spindle-shaped or oval lesion, dark color of the lesion, and the death of the whole leaf rarely occurs, which can be distinguished from downy mildew.

In warm winter areas, pathogens spread on onion and garlic crops. In cold areas, mycelium attaches to the host or diseased residue for wintering, and produces conidia in the following year, which are spread by air flow or rainwater, and the germs invade from the stomata and wounds, or directly penetrate the epidermis, and the incubation period is 1-4 days. Conidia are formed under high humidity conditions, and dew and rain are required for spore germination and invasion. The appropriate temperature for the onset is 25 -27, and the incidence is generally severe in warm, rainy or humid summers.

The local red-skinned onion has a light disease, the yellow-skinned onion is susceptible to serious disease, the disease is serious if transplanted early, the deep ditch has high moisture and fast drainage, the soil has good air permeability, the susceptibility is mild, and the hair that has been irrigated in the recent past has become heavier. There is a yellow halo around it, and after that, some expand into concentric ring spots, and when the humidity is high, there is black-brown pulverized mold on the lesions.

In the end, it will affect the yield of onions, and it will also determine the quality and size of the onions, and if the disease is severe, it will also lead to no onions.

In this way, the leaves can wilt a lot, and the incidence will be particularly high, and there will be some pests and diseases, etc., which are very serious hazards.

The initial lesions are small, gray to light brown, ** slightly purple, with black-gray mold. The lesion quickly expands to an oval or spindle-shaped, sunken, dark purple color, forming concentric ring patterns with a yellow halo around it.

Green onion purple spot disease mainly occurs in the summer and autumn of high temperature and humidity, sandy soil, dry land, insufficient fertilizer, poor management, and green thrips are serious plots, with serious disease and rapid spread.

1) Apply sufficient basal fertilizer and timely top dressing to enhance plant disease resistance; Pay attention to drainage in the rainy season, control irrigation after the onset of the disease, prevent the aggravation of the disease, and prevent and control the allium thrips as soon as possible.

2) Spray with 500 times of 75% chlorothalonil wettable powder, 500 times of 58% methamalene manganese-zinc, 500 times of 50% promethanein wettable powder, 500 times of 70% mancozeb wettable powder, and spray once every 7 10 days. Spray 3 4 times in a row. The rotation of the above agents is more effective.

It is mainly harmful to leaves. The leaves are infected with fusiform lesions, 10 30 mm long and 3 6 mm wide, gray-brown in the middle of the spots, brown on the edges, and small black spots on the spots, that is, the ascomycetes of the pathogen. In severe cases, the lesions fuse, causing the leaves to dry out locally.

It winters mainly in the soil with the diseased residues by conidia or ascomycetes: it is dispersed by wind and rain or irrigation water the following year. Invasion from wounds or natural orifices, and conidia are produced in the diseased area after onset for reinfection.

In addition, seeds can also carry bacteria, causing leaf disease. The temperature is 18-25, the relative humidity is higher than 85% and the soil moisture content is high. It is harmful in the south all year round, and the disease is severe in the rainy and humid season.

It can occur from May to October in the north.

Green onion brown spot disease, you need to see a plant specialist to help you.

Onion purple spots mainly damage the leaves. The spot is a small white spot with water stains at the beginning, mostly near the tip of the leaf, slightly concave, and then gradually enlarged, purple-brown, oval, and concentric rings can be seen. When the humidity in the field is high, a dark brown mold layer appears on the surface of the lesions.

After the lesions are fused with each other, the tissues in the affected area die and lose water, and the mechanical strength of the leaves decreases, so the leaves are often broken from the diseased area. The hindrance of photosynthesis in the leaves seriously affects the normal growth of the bulb. Purple spots mainly infect onions and green onions, but also garlic and leeks.

It mainly harms the leaves, peduncles, and bulbs on onions. Lesions begin at the tip of the leaf or form at the site of a wound destroyed by thrips. The lesions are small at the beginning, gray to light brown, with a slight purple in the center and dark gray mold.

The lesion rapidly expands into an oval or spindle-shaped, concave and dark purple color, forming concentric circles surrounded by yellow halos.

When the humidity is high, the lesions spread to the whole leaf, which often makes the green onion leaves turn yellow from the bottom to the top and die or break, which seriously affects the yield and quality of fresh onions. The purple spot fungus belongs to the subfamily Hemiptera fungi and overwinters in the soil, where the hyphium attaches to the diseased remnants. Or they are thrown on onion plants, spread by air currents and rainwater, and invade through stomata, wounds, or directly through the epidermis.

It is easy to develop disease under warm and humid conditions, and it is easy to develop disease in bulb expansion stage, and it is serious when sandy soil, dry land, early seedlings, old seedlings, lack of fertilizer, weak onion growth, and thrips are seriously harmed. The local red onion suffers from a mild ailment, while the yellow onion suffers from a severe ailment. Early transplantation can lead to serious disease.

The deep ditch drains quickly and has a high water content. The soil is permeable and the disease is light. In the near future, the hair after rinsing will become heavy.

To prevent and control onion purple spot disease, it is necessary to clean the countryside. Before planting onions, the field should be completely removed from weeds, diseases and other infectious sources, and taken away from the field for burning. In addition, the whole garden should be deeply turned over and disinfected to effectively reduce residual germs in the field.

After the seedlings are unearthed, a new high-lipid film is sprayed in time to isolate the infection of germs, improve the onion's natural disaster resistance and photosynthesis intensity, and protect the plant from thriving. Control thrips and other pests in the field in time, avoid plant wounds, and reduce the infection rate of purple spot. The main thing is to damage the leaves.

Lesions are initially white spots with water stains, then turn hazel, round or spindle-shaped, slightly sunken spots that continue to expand into brown or dark purple with yellow halos around them. The disease grows into a mold arranged in concentric circles in dark brown or dark gray and continues to expand, causing the entire leaf to turn yellow, die, or break.