In the agronomy of garlic cultivation, there is a natural yellowing associated with the end of the growing season, which occurs causally when violations of planting rules lead to diseases or deviation from the norms of physical-biological development during the growing season due to damage by pests.
To identify the causes of garlic leaves turning yellow, consider the possible causes in this article and provide positive and consistent ways to protect the crop from negative factors that affect garlic yield and quality.
CAUSES OF GARLIC LEAVES TURNING YELLOW
Garlic is divided into 2 groups – spring garlic and winter garlic. Yellowing of spring leaves is more common in winter garlic. The causes of yellowing can be broken down as follows.
- Stress factors caused by violation of agronomic cultivation techniques.
- Infection of plants by fungal and microbial microbiota.
- Pest infestation.
Violation of cultivation rules that cause garlic leaves to turn yellow
In order to identify the causes and take timely measures to protect the garlic from premature yellowing of leaves, it is initially necessary to clearly observe all agronomic cultivation techniques:
- Soil preparation and fertilization.
- Selection and preparation of planting materials.
- Proper planting.
- Care during the autumn, winter, and spring/summer periods.
Consider the possible violation of agricultural techniques that can lead to the yellowing of garlic leaves. If the yellowing of garlic leaves is caused by violation of agricultural techniques, good care, timely fertilization and watering will compensate for the lack of care and the plant will provide a decent yield of garlic heads after the formation of new shoots.
Acidification of the soil
Garlic is a crop that requires neutral soil. With the prolonged application of mineral fertilizers, the root-bearing layer of the soil becomes slightly acidified, to which garlic reacts by turning the leaves yellow, as some of the nutrients are not available through the root system. In this case, the plant uses the nutrients in the leaves for development.
Before planting garlic, it is necessary to apply wood ash to the soil at a rate of 1-1.5 cups per 11 square feet of area and to re-till the soil. Keep in mind that ash applications should not be combined with mineral fertilizers.
Fertilizer is applied at the time of re-tillage, ash – before planting tubers and vice versa, but the time difference is not less than 2-2.5 months. It is possible to use dolomite powder or limestone for deoxygenation. In rotational planting, it is prescribed to apply organic fertilizer under the previous one.
Poor quality planting material and planting errors
When planting, make sure that only large and healthy planting materials are selected. Garlic cloves should be disinfected with manganese or other methods beforehand.
After preparing the soil, form a bed for planting. If necessary, water over the furrows. Plant the garlic cloves at a depth of 1.5-2inch (4-5 cm).
With different sizes of planting material, germination will be uneven, which will cause seedlings to respond differently to the effects of the environment. Strong plants will tolerate temporary changes in temperature and humidity. Weak ones (from small cloves) will lag behind in development and may die completely.
In shallow plantings, garlic may be partially frozen by back frost, especially if there is no snow cover or if it thaws quickly. In cold soils, the root system does not work and the plant absorbs nutrients from the leaves to maintain growth and development. Externally, this stressful situation manifests itself as yellowing of the leaves.
If garlic cloves are planted too deeply, the soil does not have time to warm up sufficiently for the root system to work and the leaves begin to turn yellow.
To prevent weather conditions from adversely affecting your plants, you should cover your plants with film overnight in the spring until the frost period has passed. To improve the resistance of the crop to weather fluctuations, it is necessary to treat the plants with any biostimulants (epi- and others).
Violation of the planting date of garlic
Garlic should be planted at the recommended time.
Planting garlic too early promotes the formation of above-ground masses, which are more subject to weather conditions.
If garlic is planted too late, the root system does not have enough time to form and the plant reacts quite painfully to any changes in environmental weather conditions.
Violations in garlic care in autumn and winter
In southern regions, where autumn is often long and dry if necessary, it is necessary to water plants covered with mulch with a small amount of water.
In winters with long frosts, it is better to cover the garlic bed with extra snow or to toss it with branches that retain snow. Positive results can be obtained by planting garlic in sumac, which plays the role of mulch – both a green fertilizer and a snow accumulator.
Incorrect fertilization of garlic
The yellowing of garlic leaves in spring may be caused by a lack of nitrogen nutrients. To keep the nitrogen in the root-containing layer and not in the lower layers with water, you need to use ammonium sulfate or urea as part of a complete fertilizer for garlic when you prepare the soil in the fall.
If no fertilizer is applied from autumn (for various reasons) and in early spring when the leaves of garlic start to turn yellow, the first fertilizer for garlic should be a nitrogen fertilizer, and once the plants start to grow, further fertilizer is applied according to the agricultural technique of this cultivation.
In rainy spring, it is better to feed with nitrogen in the form of ammonium and amide (urea, ammonium sulfate).
If the weather is dry, it is more practical to feed garlic with ammonium nitrate pre-dissolved in water (20-25 g/2.6 Gal of water heated in the sun).
Some gardeners use grass ashes at the first feeding in spring, 100-150 g/11 sq ft. Ash contains high levels of trace elements, including potassium and magnesium, deficiencies of which can also cause garlic leaves to turn yellow. Ash has a positive effect on the growth and development of the root system, above-ground parts, and hoarding organs.
If grass ash is applied in autumn and garlic leaves start to turn yellow in spring (under all other positive conditions), this means that several elements are missing or their ratio is disturbed. In this case, it is better to make nitroaminophoska, azoxystrobin, nitrophoska in the form of a solution or other complete fertilizer at a dose of 25-30 g/11 sq ft, according to the recommendations.
Method of fertilizer application.
- The nutrient solution is applied in furrows, cut between rows of garlic, and covered with soil or mulch.
- Some gardeners recommend applying the nutrient solution by irrigating the entire area occupied by the garlic.
- Fertilizer applied through shallow loosening is incorporated into the soil or applied under irrigation.
The method of fertilizer application depends on weather conditions and the owner’s preference.
Garlic is not watered correctly
Yellowing of the leaves of garlic may result from insufficient moisture content in the soil. Particularly severe leaf discoloration has been observed in young plants. Therefore, water regularly and adequately from April to June (depending on the region) as the plants develop and the cloves set and grow. The water must be fresh and warm in the sun.
Also, garlic does not tolerate waterlogging and frequent rainfall requires drainage ditches along the garlic planting rows. After watering, the soil should be covered with mulch and further watered over the mulch so as not to expose the forming heads to the sun.
If the agronomic requirements are met on time in terms of quality, but the garlic leaves are yellowing and more and more plants are covered, there is no doubt that the planting is affected by pests and diseases. In this case, it is necessary to.
- Check carefully the stems and leaves of garlic.
- Dig out several plants in different places and check the root system and garlic heads.
- Use a reference book to determine the name of the disease or pest and the preparation for protection.
- If you have diseases and pests on the same plant, prepare mixed jars of treatment plants and check their compatibility beforehand.
GARLIC DISEASES THAT ACCOMPANY YELLOWING OF LEAVES
Garlic diseases that cause yellowing of the leaves include
- White rot and basal rot.
- Aspergillus niger.
- Blue or green Penicillium.
- Fusarium wilt.
- Garlic rust.
Rust, mildew and dew are fungal-bacterial diseases. They affect plants mainly at the arrival of warm and humid or dry and hot weather, during which mycelium grows intensively in the soil and on the ground. At that time, sporangia with spores (ASCII) are formed, initiating a new infestation. Some spores survive in the soil for 25 to 30 years.
Therefore, if garlic leaves turn yellow and light white-gray downy fungal growth is found at the base of the leaves, along the stems, roots, and gears, treatment should be started immediately.
Control measures for diseases causing yellowing of garlic leaves
The yellowing of garlic leaf tips, which spreads rapidly throughout the leaf disc and increases the number of yellowing plants on-site, is clear evidence of a fungal disease affecting the plant.
If the fungus is found during the dry period, it is necessary to increase soil moisture by watering. It is best to water the garlic bed with ammonium nitrate solution to increase the resistance of the plant to the infection.
Fusarium, powdery mildew, and some rots can appear rapidly on garlic during humid periods with high air temperatures. To prevent it, it is necessary to loosen the soil to reduce its water content. Fertilization can be carried out, and more practically. The content of trace elements on the foliage.
In order not to bother with the definition of each disease and the individual selection of drugs that protect the plant from each disease, it is better to turn to biological agents.
An effective way to stop diseases is to treat plants with biological agents that are healthy and harmless to family members, animals, beneficial insects, and other small animals. Such agents include bio fungicides, including.
- Natural biological fungicides – when affected by powdery mildew, rust, phytophthora, root rot.
- Trichodermin – for root rot (white, gray, black)
- Ampicillin – for powdery mildew control.
- Mycotoxin – increases the activity of underground positive microflora and enhances the immunity of plants to diseases.
The use of listed bio fungicides in tank mixtures reduces the number of treatments, improves disease resistance of garlic, and promotes the formation of sufficiently high yields of healthy garlic bulbs. Plants and soil are treated with biocides. Preparation of the tank mixture and treatment of plants and soil must be carried out in strict accordance with the recommendations.
Note! If garlic plants are infested, it will take 4-5 years to replant them.
PESTS THAT CAUSE YELLOWING OF GARLIC LEAVES
Garlic is affected by a number of pests that can damage the crop if reproduction is not controlled: Ditylenchus dipsaci, Delia Antiqua (Onion Fly), onion miner, onion leaf beetle, root mite, onion flea, etc. The most pernicious pests of garlic are Delia Antiqua (Onion Fly) and Ditylenchus dipsaci.
Delia Antiqua (Onion Fly)
Remember! When garlic is attacked by Delia Antiqua (Onion Fly), the leaf tips start to turn white and wilt.
The pest overwinters in the soil in the form of nymphs. As Delia Antiqua (Onion Fly) begins to fly in April or early May, it lays eggs on the ground at the base of the garlic plant. Within three to eight days, the hatched larvae penetrate the young cotyledons, settle in the true stem (stalk), and begin to feed on the plant sap. Affected plants first wilt, then turn yellow and die.
Preventive measures to protect the garlic from Delia Antiqua (Onion Fly):
- Plant carrots and onions in mixed rows in a bed. Around the bed, you can plant mint, cloves, marigolds, and other plants with strong odors to repel the pests.
- The soil is systematically loosened to a depth of no more than 1-1.5inch (3-4cm).
- Sprinkle a mixture of 0.5 cups of wood ash, one tablespoon of tobacco powder, and 1 teaspoon of pepper (consumption per 11 square feet of area) in the soil around the plants.
- You can sprinkle a mixture of tobacco powder and sunflower ash, or a mixture of tobacco powder and lime powder between the rows.
- Sprinkle garlic plants effectively with a weak solution of copper sulfate: dissolve 1 tablespoon of the drug in hot water and mix it with 2.5 Gal of cold water.
Take active measures to control Delia Antiqua (Onion Fly) on garlic.
To avoid health hazards, the use of chemicals under garlic is not recommended. Use caution when treating plants and soil with chemicals during the vegetative phase of the crop.
In the approved method of controlling Delia Antiqua (Onion Fly) on garlic, carry out.
- spraying garlic with a solution of ammonium carbonate nitrogen salts; this treatment not only helps to protect plants from Delia Antiqua (Onion Fly), but also gets rid of powdery mildew, brown spot, and yellow spot.
- Water the soil beneath the plant with a solution of urea; if the solution gets on the leaves of the plant, it should be rinsed with water to avoid chemical burns.
- Mix 30 ml of ammonia alcohol with 2.5 Gal of cold water and make shallow furrows along the rows of garlic; the ammonia can be replaced by 200 g of rock salt. (Remember! Salt accumulates in the soil and can affect plants subsequently planted in rotation).
In recent years, a number of biopesticides have been developed that have successfully controlled pests. Such biopesticides include biopesticides “insecticidal fungal preparations”. Their use is effective when treating plants and soil according to recommendations.
Infestation of garlic plants by Ditylenchus dipsaci occurs most often in the humid, cool summer months. Tiny Ditylenchus dipsaci larvae settle in the tissues of infected plants. ditylenchus dipsaci disease develops. The growth of the plant begins to lag. The stems of pseudogarlic thicken and become covered with white, then brown longitudinal stripes and the leaves begin to turn yellow.
A distinctive feature of garlic infested with Ditylenchus dipsaci is that the underside shrivels and the teeth of the garlic bulb become loose. The overall destruction of the garlic bulb is observed and a peculiar odor is acquired. The larvae leave the diseased, decaying plant and move rapidly to new areas.
What are the characteristics of Ditylenchus dipsaci
- It penetrates the pseudostems and true stems (stolons) of garlic, which begin to rot; the roots are hardly damaged, but they die due to stem rot.
- On young plants, the leaves curl into a tubular shape, turn yellow, and then fall off.
- During a primary infestation, small cracks may appear around the base of garlic as a result of parasite larvae multiplication.
- Dried scales of cloves turn yellow during storage; dry rot appears on the cloves.
- Ditylenchus dipsaci hairs on garlic cloves and bulbs are not mold, but thousands of Ditylenchus dipsaci larvae.
- Plants infected with Ditylenchus dipsaci smell like rotting onions and garlic in wet weather.
Preventive Ditylenchus dipsaci control methods
- Plant only healthy planting material.
- Compulsory disinfection of planting material.
- After harvest, all residues should be burned or sent to compost; storage facilities should be disinfected with bleach or Formaldehyde.
- Send garlic back to the same field no earlier than 4-5 years.
- Be sure to introduce dolomite powder or other soil deoxidizers; in neutral soil, Ditylenchus dipsaci will lose its speed of movement and will freeze.
- Some gardeners treat the soil with a 1% solution of baking soda before planting.
- The number of Ditylenchus dipsaci in infested areas can be greatly reduced by planting trap plants (spring rape, vetch, soybeans, peas, beans, and pulses); pull out and burn adult plants along with the pest-infested roots.
- Systematically inspect and cull diseased plants.
- Spray the plants with copper sulfate solution.
It should be noted that all preventive measures carried out against Delia Antiqua (Onion Fly) will also affect Ditylenchus dipsaci to some extent, leading to its death.
Active control of Ditylenchus dipsaci
In order to keep fields free of Ditylenchus dipsaci infestation, it is necessary to eliminate it from entering the soil with infested planting material. In the vast majority of cases, the infestation of the soil occurs by planting diseased planting material. To avoid this, the planting material must be carefully disinfected.
A pest control technique for planting material that does not reduce the plant’s ability to germinate can be provided for your consideration.
- Soak the planting material in a quantity of water heated to 100°F (38°C) for 1 hour.
- Add Formaldehyde and garlic cloves to this solution. The amount of Formaldehyde added should be such that its content in the solution increases to a concentration of 1%.
- Increase the temperature of the 1% Formaldehyde and garlic clove solution to 120°F (49°C) and incubate the plants at this temperature for 20 minutes (maximum).
- The decontaminated planting material is washed in cool water, dried, and planted in the field.
Decontamination of garlic can also be done by ash soaking, manganese, 1% salt solution, and other methods.
Kaolin or bentonite clay can be used before planting. The powdered mineral is mixed with topsoil. In this way, Ditylenchus dipsaci will escape from the treated area.
Urea is applied between the rows of garlic, followed by a fine encrustation. Ammonia accumulated in the stems is toxic to Ditylenchus dipsaci larvae.
Nitrogen dressing has a negative effect on larvae (not only Delia Antiqua (Onion Fly) but also Ditylenchus dipsaci).
Some gardeners treat the soil under the garlic with a salt solution (200 g/2.5 Gal water) or an ammonia solution (30 ml/2.5 Gal water). After soil treatment, the plants must be washed with clean water to prevent chemical burns on the leaves.
Among the chemical methods of controlling Ditylenchus dipsaci, it can be recommended to treat the soil and garlic with biopesticides. The use of chemical agents is undesirable (even if authorized) because they can negatively affect human health if the rules of preparation of solutions and treatment of plants are violated.
Among biopesticides, abamectin-C, abamectin-N, pexilomycin, and methomyl are effective against Ditylenchus dipsaci. It is important to follow the recommendations carefully when using biocides. If you deviate in dilution and application (without taking into account temperature, humidity, and other requirements), the positive effect will be negligible.
The recommended material reveals only measures to control the main pests and diseases of garlic, the external manifestation of which is the yellowing of the plant. As you learned from the article, the main protective measures are preventive ones. Biological agents are effective as long as they are strictly followed.
On your small farm, you can exclude chemical agents from the means of protection. Please share with our readers your “secrets” for successful control of the dreaded pests and diseases of garlic.
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