This year's garlic is very sharp, yellow, and rotten. What is the reason?

This year, many farmers who grow garlic are responding to a problem, saying that this year's garlic dry sharp yellowing phenomenon is more serious, and some underground also appear to rot. In fact, the problem of yellowing of garlic is every year. In order to get the medicine right, it causes yellowing of garlic. There are actually many reasons.

First, physiological reasons

1. Insufficient nutrient supply

(1) Dry tip yellowing in the "bad mother" period

The "bad mother" mainly refers to the process in which the growth of garlic is transferred from the supply of nutrients to the roots to absorb nutrients.

At this time, the nutritional supply and demand of the garlic seedlings are not balanced, and yellow leaves will appear, and the color will be from shallow to deep until the dry tip is produced.

note:

This physiological phenomenon usually occurs on the 1--4 leaves in the lower part of the plant. The red-skin garlic occurs in the six-leaf stage, and the white-skin garlic occurs in the ten-leaf stage.

(2) Insufficient nutrient supplementation, yellowing will occur when there is a deficiency

E.g--

In the absence of calcium, necrotic spots appear on the leaves. As the necrotic spots expand, the leaves bend down and the tips of the leaves die quickly.

In the absence of magnesium, the leaves are chlorotic, first appearing at the base of the old leaves, gradually developing toward the tip of the leaves, and the leaves eventually turn yellow and die.

In the absence of boron, the new leaves are yellowed. In severe cases, the leaves die, the growth of the plants is stagnant, and the anatomical leaf sheaths are brown and cracked.

Prevention:

Understand the fertilizer requirements and fertilizer characteristics of garlic, and do topdressing when appropriate.

Garlic needs fertilizer rules:

The absorption of nitrogen by garlic is mainly in the middle and late stages, and the absorption of phosphorus and potassium is mainly in the early and middle stages. Starting convulsions (the bulbs begin to expand) is a critical period of fertilization. In addition, the root system of garlic is shallow and the absorption capacity is weak. It is necessary to apply enough base fertilizer, especially the decomposed organic fertilizer.

2. Unusual climatic and environmental conditions

(1) Unsuitable temperature conditions

Garlic is a cold vegetable, and the suitable temperature for stem and leaf growth is 12-16 °C. When the temperature reaches above 26 °C, the leaves breathe vigorously, the water transpiration is large, and the nutrient consumption is high. At this time, yellow leaves are produced at the top of the upper leaves of the plant, and gradually develop from the tip to the base, and then the dry tip appears.

If you encounter dry hot air, the damage to the leaves is heavier. In the winter, there will be chilling damage, freezing damage or the effects of cold spring after the fall, and yellowing and dry tips will also appear.

(2) Unsuitable moisture conditions

There is a lot of water in the soil, including (too much watering or rainy weather). The soil has high humidity and poor gas permeability, which may lead to roots and yellowing. Soil drought, plant water shortage can also cause yellow leaves, which is common in winter and spring seasons with less rainfall.

Prevention:

(1) There is a suitable temperature range for ensuring the growth of garlic. When the temperature is high, it can be cooled by pouring small water or proper shading, and the insulation measures are taken in winter to prevent freezing damage.

(2) When the soil moisture is large, especially after the rain, it is necessary to dig trenches in time to prevent roots and dead seedlings. Watering during the dry season.

3. Inappropriate management

(1) Improper fertilization

Excessive use of chemical fertilizers, less use of organic fertilizers, leading to acidification of the soil, causing the garlic leaves to grow slowly, thin, and the outer leaves are yellow. The growth of garlic is more suitable for neutral soil, and the optimum pH is 7.0-7.4.

(2) Repeated years

Repeated planting in successive years, soil diseases are serious.

Precaution:

(1) Improve soil acidification, properly apply organic fertilizer, and reduce fertilizer use.

(2) It is best to carry out the cropping of the crops, especially for heavy crops that have been severely affected in previous years. It is necessary to carry out rotations with non-onion and garlic crops for more than three years.

4. Other reasons

(1) Toxic gas hazards

First, the application of ammonium bicarbonate will cause ammonia damage, causing the tip of the leaf to wither and gradually turn brown.

Second, the factory emits exhaust gas (CO) causing the leaves to quickly lose green, the leaves begin to turn grayish white, the leaves are yellow in the later stage, and the diseased parts have no symptoms such as mildew.

(2) Physiological de-fertilization

Often occurs in the early stage of garlic growth. After about 20 days of garlic emergence, the tip of the leaf began to lose green to brownish brown, and the tip of the leaf was yellowish. The field showed uniform disease and no central disease. At this time, the nutrients stored in the garlic have been used up, and the flower buds and the garlic stalks begin to differentiate. If the fertilizer is not timely, the yellow leaf phenomenon will occur.

(3) Phytotoxicity, it will also cause yellowing and dryness.

Second, pathological reasons

Garlic leaf blight, blight, bacterial soft rot, gray mold, white rot, virus disease will also appear yellowing, dry tip, rot and so on.

Garlic leaf blight

Incidence period:

The incidence of the adult stage is the most serious. The northern region mainly occurs in October-November and March-May, and the south mainly occurs around the Meiyu season.

Leaf damage usually begins at the tip of the leaf. The early stage of the lesion is a small dot, which then expands rapidly, is oval or irregular, and the lesion is grayish or taupe.

When the humidity is high, there is a black mold on the top, and the leaves die when it is severe.

Chemical control:

In the seriously ill field where leaf blight often occurs, it is necessary to prevent it early. The available agents are copper citrate, carbendazim, methyl thiophanate, and ether oxystrobin.

2. Garlic disease

The continuous land mass, the soil is sticky, the drainage is poor, the planting is too dense, the long-term low temperature, and the onset is heavier when the rain is continuous.

At the beginning of the disease, water-stained dark green lesions appear on the leaves. The lesion will soon spread to the entire blade, and then the blade turns yellow and sagging.

Severe, the lesion will spread to 1/3 to 4/5 of the whole leaf, or the whole leaf will die dry. When the humidity is high, the disease minister has grayish mildew.

Chemical control:

The evil cream manganese zinc, metalaxyl manganese zinc, frost urea manganese zinc, azole ether, and enoylmorpholine.

3. Garlic gray mold

Garlic gray mold occurs more in the shed. Even the cloudy days, the temperature is low, the humidity of the protection ground is large, and the wind is not timely and prone to disease. Garlic clams are cold and highly humid when harvested, and are most susceptible to gray mold.

The main damage to the leaves, the edge of the lesion is not clear, the occurrence of serious in the plant, half from the tip of the tip will be yellow.

When the humidity is high, the surface of the lesion will be covered with a gray furry mold layer.

Chemical control

(1) In the growth phase, in the early stage of the disease, thiazole, polymethine, pyrimethanil and other agents can be used.

(2) During the storage period, 25% prochloraz aqueous emulsion can be diluted 250~330 times, and the garlic tips are immersed for 1~2 minutes, then removed and dried, and then stored at 0 °C or above.

4. Garlic white rot

Leaves, sheaths and bulbs can all develop disease.

In the early stage of the disease, water-stained lesions appear, and the diseased part becomes soft and ulcers rot. When the humidity is high, the surface grows white hairy hyphae. When the time is long, sclerotia will form, and the decayed part will emit strong garlic. Stinky.

Chemical control

You can choose isourea, carbendazim, thiophanate-methyl, and acesulfame. Once every 7 to 10 days. In particular, the diseased part of the bulb in the plant, the drug should be sprayed on the root.

5. Garlic bacterial soft rot

Leaf symptoms:

Beginning with the leaf margin or midrib, yellow-white streaks are formed along the leaf margin or midrib, and streaks can penetrate the entire leaf. When the humidity is high, the diseased part is yellowish brown soft rot, there will be yellow bacterial liquid overflow, and there is a foul smell.

In general, the lower leaves of the plant first develop, and then gradually expand upward, and finally the whole plant is yellow or dead.

Chemical control:

Thiobacillus copper, copper hydroxide, scleromycin, neutrophin, leaf azole and the like.

note:

(1) The application method can be spray or root irrigation.

(2) The effect of rooting is better than spraying, but if the soil moisture is high, it is not appropriate to use root irrigation.

(3) When spraying, be careful to spray on the base and root of the stem, and spray the plant on the diseased plant and its surrounding plants.

6. Garlic sclerotinia

The disease mainly harms the base and bulb of the garlic stem.

At the beginning of the disease, the lesions were water-stained, and then the lesions became dark or grayish white, the ulcers rotted, and a strong garlic odor was emitted. The wilting of the leaves on the ground gradually yellowed and died. The roots of the garlic must be rotted. When the humidity is high, the surface grows white hairy hyphae.

Chemical control

Pythium, carbendazim + tebuconazole, thiabendazole, iprodione, cyprodinil, boscalid and other agents spray control.

General control measures for several diseases

(1) Disease-resistant varieties

The prevention and treatment of diseases should be based on the premise of planting disease-resistant varieties, strengthen cultivation management, and timely supplement with pharmaceutical treatment.

(2) Rotation

In agricultural control, it is best to carry out crop rotations, especially for heavy crops that have been severely affected in previous years. It is necessary to carry out rotations with non-onion and garlic crops for more than three years.

If there is no condition for rotation, in addition to disinfection of the garlic before planting, it should also be noted that early prevention.

(3) Strong seedlings

The prevention and treatment of diseases is fundamentally to improve the disease resistance of garlic. In the seedling stage, it is necessary to control the seedlings, and properly carry out seedlings to cultivate strong seedlings.

(4) Field drainage

It is necessary to use sorghum planting, and rational irrigation and drainage to avoid water accumulation in the field. This kind of cultivation method can best show advantages when it encounters continuous rainy weather.

Third, pests

Garlic damage

Generally, larvae eat garlic bulbs, causing the bulbs to rot, and the upper leaves are yellow, wilting, and even dead.

Pull out the victim strain and find 蛆蛹

Damaged garlic: the garlic skin is yellowish brown and rot;

Garlic: It is broken into holes by larvae, and the incompleteness is incomplete;

Garlic cloves: bare, cracked, and stinky.

Prevention:

(1) Choose healthy garlic

This can shorten the emergence period of garlic, ensure the seedlings are robust, and shorten the time of the stagnation, effectively reducing the root mites.

(2) Rotation and fertilization

Implement garlic and wheat rotation, and do a good job of deep fertilization. Garlic and wheat rotation can effectively reduce the insect base. The autumn ploughing is deep, using fully decomposed organic fertilizer, and the fertilizer is separated from the garlic, which can effectively control the root mites.

(3) Chemical control

The beginning of the larvae:

Remove the spray nozzle with 50% phoxim emulsifiable concentrate 500 times solution and 90% trichlorfon 1000 times solution, and administer the garlic base. It is inoculated once every 10 days, and the insects are irrigated for 2 to 3 times.

Adult origination period:

Adults were killed with 50% phoxim emulsifiable concentrate 1000 times solution, or 50% dichlorvos 1000 times solution, or chlortetracycline spray. Spray once every 7 days for 2 to 3 times.