Diagnostics

1. Systematic Inspection: From Leaves to Bulb

Begin your inspection from the top of the plant and proceed downwards. Each level can reveal different problems.

• Leaves. These are the "mirror" of the garlic's condition. Color, shape, spots, and coating are the first and most obvious signs. Yellow, white, curled, or drying leaves indicate a wide range of problems: from nutrient deficiency to disease or pest infestation (Brewster, 2008).
• Stem (false stem) and neck. Assess their firmness and color. Softening, darkening, or the presence of a coating at the base of the leaves can indicate fungal infections such as Fusarium or White Rot (Entwistle, 1990).
• Roots. This is the "foundation" of the plant's health. Healthy roots are light-colored, firm, and well-branched. Examine the root system by gently pulling up one or two suspicious plants. Darkened, rotting, or underdeveloped roots are a clear sign of a problem (Brewster, 2008).
• Bulb (head). Its condition is the final diagnosis. Assess the bulb's firmness, the quantity and quality of the outer skins, and the presence of damage or rot. Only after harvest can you fully assess the extent of the problem (Rabinowitch & Currah, 2002).

2. Considering the Growth Stage and Season

The same symptom can mean entirely different things at different times of the year. Ignoring this factor is the most common mistake.

• Spring (active leaf growth). Even minor deviations require close attention. Yellow leaf tips in April-May are almost always a stress signal (cold, nutrient deficiency, waterlogging) and require immediate intervention (Brewster, 2008).
• Mid-summer (beginning of maturation). Yellowing and drying of the lower leaves during this period is a natural process signaling bulb maturity. At the same time, yellow leaves can also be a sign of pest damage, such as the onion fly, or diseases, requiring differential diagnosis.
• Autumn (for winter garlic). It is important to assess the seedlings and their readiness for winter. Weak, yellowed seedlings indicate problems with rooting, which can lead to poor overwintering (Miedema, 1994).

Always ask yourself during diagnosis: "Does the condition of this plant correspond to its natural development cycle?" The answer will help separate normal from pathological and choose the right solution.

Nitrogen Deficiency

Symptoms: Leaves become light green, then uniformly yellow, starting with the older, lower leaves. Plant growth slows down, and it appears weakened. This process starts at the leaf tips and spreads towards the base. Yellowing due to nitrogen deficiency often appears during the period of active growth when the plant is developing a robust leaf apparatus (Brewster, 2008).

Why it works: Nitrogen is a key element for synthesizing chlorophyll, protein, and green mass growth. When deficient, the plant redistributes nitrogen from old leaves to new ones, causing the older ones to yellow. Younger leaves may remain green longer (Brewster, 2008).

What to do: Apply a nitrogen fertilizer. For organic gardening, a manure or poultry manure infusion, or blood meal, is suitable (Engeland, 1991). From mineral fertilizers, you can use urea or ammonium nitrate. Be careful not to overdo it, as excess nitrogen can delay bulb formation and reduce storage life. Fertilizing is best done in the first half of the growing season.

Waterlogging and Soil Compaction

Symptoms: Leaves become yellow, may droop, and lose turgor. Plants appear depressed, especially after rain or watering. When pulled out, such plants may have darkened, rotting roots, and the soil may have an unpleasant, sour smell. This is often accompanied by fungal diseases developing on the roots (Brewster, 2008).

Why it works: Garlic is sensitive to stagnant water. Garlic roots need access to oxygen for respiration. In waterlogged soil, oxygen is displaced by water, roots "suffocate," stop absorbing nutrients, and the process of rotting begins. Under such conditions, roots become vulnerable to pathogenic fungi like Fusarium spp. (Brewster, 2008).

What to do: Normalize your watering schedule. Garlic needs 1-2 deep waterings per week in dry weather, and watering should be completely stopped during rainy periods. If the soil is heavy clay, improve its structure by adding sand, compost, or well-rotted manure to enhance drainage. Consider planting garlic on raised beds (Engeland, 1991).

Fusarium (Basal Rot, Fusarium Rot)

Symptoms: Leaves yellow starting from the tips, and the process progresses rapidly downwards. The plant may suddenly wilt. A pinkish, whitish, or yellowish-brown coating of mycelium appears on the bulb's base. When dug up, the bulb is soft, with rotting roots, and a coating may be visible between the cloves. This disease often begins to show in the second half of the growing season (Rabinowitch & Currah, 2002).

Why it works: Fusarium oxysporum f.sp. cepae is a soil-borne fungus that penetrates the roots and the base of the bulb. It clogs the plant's vascular system, disrupting water and nutrient transport, causing yellowing and wilting. The fungus is active at high soil temperatures (>25°C). Infection often enters through mechanical damage to roots or the bulb (Brewster, 2008).

What to do: Prevention is the best treatment. Use only healthy, certified planting material. Practice crop rotation (do not return onions or garlic to the same spot for at least 3-4 years). If diseased plants are found, remove and burn them immediately to prevent spread. In the early stages, biological products based on Trichoderma or Bacillus subtilis may help (Brewster, 2008).

Natural Senescence and Maturation

Symptoms: Yellowing starts with the lowest, oldest leaves, gradually moving to the ones above. Leaf tips turn yellow and dry out, but the plant's overall condition remains satisfactory, and the bulb is firm. This process moves from bottom to top and usually coincides with the variety's maturation time – from late June to August (Engeland, 1991; UMN Extension, 2024).

Why it works: This is a natural physiological process. As bulb formation nears completion, the plant begins to redistribute nutrients from the leaves to the bulb. Old leaves have fulfilled their function and are dying off.

What to do: Nothing. This is normal. It's important to distinguish natural yellowing from stress-induced yellowing. If you observe this at the right time and the bulbs look healthy – get ready for harvest. Timely harvesting (when about half or slightly more of the leaves are still green) ensures good storage life (UMN Extension, 2024).

Stem Nematode (Ditylenchus dipsaci)

Symptoms: This yellowing has a characteristic pattern. Leaves don't just turn yellow; they become chlorotic, curl, deform, and thicken. Blisters may appear on them. Plants are severely stunted. Brown or gray areas appear on the bulbs, and the skins crack. With severe infection, the bulb neck softens, and the head disintegrates (Brewster, 2008).

Why it works: The nematode is a microscopic worm that penetrates plant tissues and feeds on their contents. In response to the damage, tissues proliferate, causing deformations, and the enzymes secreted by the nematode break down cell walls, leading to yellowing and tissue death (Engeland, 1991).

What to do: Controlling nematodes is extremely difficult. It is a quarantine pest. Main measures are preventive: use only healthy planting material, heat-treat cloves before planting in hot water (45°C for 2-3 hours) (Brewster, 2008). Practice strict crop rotation, do not return garlic or onions to an infested area for at least 4-5 years. Remove and burn affected plants.

How to Distinguish Causes of Yellowing?

For quick diagnosis, use a simple visual test:

• Uniform yellowing of old leaves, slow growth → likely Nitrogen deficiency.
• Yellowing of all leaves after watering/rain, soil is wet → Waterlogging.
• Yellowing and wilting with pinkish coating on the bulb → Fusarium.
• Deformation, curling of leaves with yellowing → Nematode.
• Yellowing of lower leaves at the end of the season → Natural maturation.

Sunburn

Symptoms: Discolored, whitish or straw-yellow patches appear on the leaves, often as spots or streaks. They may be concentrated on the upper side of the leaves, most exposed to the sun. Tissues in these areas become dry, brittle, and may die off. Whitening is often observed after a sudden change in weather – after a long cloudy spell, a hot, sunny period arrives (Engeland, 1991).

Why it works: Sunburn is physical damage to tissues caused by ultraviolet radiation. When a plant is not adapted to intense sunlight (e.g., after cloudy weather or after abruptly removing mulch), chlorophyll is destroyed faster than it can be replenished. Leaf tissues overheat, cells die, leading to discoloration. Young, tender leaves and plants weakened by other factors are particularly vulnerable (Brewster, 2008).

What to do: Prevention involves gradually acclimating plants to the sun. When planting garlic in open areas, avoid abruptly removing protective covers in spring. If using mulch, remove it gradually to allow plants to adapt. On hot, sunny days, provide adequate watering to reduce stress. Damaged leaves won't recover, but new growth will be healthy.

Iron Deficiency (Chlorosis)

Symptoms: Young leaves become pale green, then almost white or creamy yellow, while the veins remain green. This is a characteristic picture – a green network of veins on a whitening leaf blade. Affliction starts with the upper, youngest leaves, unlike nitrogen deficiency which affects old leaves (Brewster, 2008).

Why it works: Iron is necessary for chlorophyll synthesis, but it is immobile within the plant. When deficient, young leaves cannot obtain enough iron from older tissues, so they are affected first. Iron deficiency often occurs not from its absence in the soil, but from its unavailability. This happens on alkaline soils (high pH), in waterlogged or compacted soil, and with an excess of phosphorus or manganese (Brewster, 2008).

What to do: For quick correction, use a foliar spray with iron chelate (e.g., "Ferovit" or "Micro-Fe"). Foliar application provides a rapid effect as iron is directly absorbed into the tissues. For a long-term solution, lower the soil pH (by adding sulfur or acidic fertilizers) and improve drainage. Adding organic matter (compost, well-rotted manure) also improves iron availability (Brewster, 2008).

Root Damage (Physiological or Mechanical)

Symptoms: Leaves turn white or pale green, lose turgor, and may wilt. Whitening is often accompanied by stunted growth and general plant depression. When pulled out, a weak, damaged, or rotting root system is found. This can result from deep cultivation, waterlogging, drought, or soil pest activity (Brewster, 2008).

Why it works: Roots are the primary organs for absorbing water and minerals. When the root system is damaged, the plant cannot obtain sufficient water and nutrients, even if they are present in the soil. This leads to water and nutrient stress, disrupting chlorophyll synthesis and causing leaf discoloration. The white color here results from tissue death due to dehydration and starvation (Engeland, 1991).

What to do: Cultivate carefully to avoid damaging garlic roots, which are located close to the soil surface. Normalize watering – avoid both drought and waterlogging. If damage is caused by pests (e.g., onion fly larvae or mole crickets), take measures to control them using approved insecticides or biological products. Root feeding with phosphorus-potassium fertilizers and root growth stimulants (humates) can help root recovery.

How to Distinguish Causes of Whitening?

Use a simple visual test:

• White spots on the upper leaf surface, often after sunny weather → Sunburn.
• Young leaves pale, veins green → Iron deficiency.
• Plant wilts, leaves whiten, soil dry or conversely very wet → Root damage.
• Leaves turn white and curl – this is the next symptom and may indicate other problems (e.g., viral diseases or herbicide stress), which we will cover in the following chapters.

Lack of Moisture (Drought)

Symptoms: Leaf tips dry out, becoming brown or straw-yellow, and curl. The process starts with the oldest, lower leaves and gradually moves upwards. Leaves lose turgor, become limp, especially during the hot part of the day. Plants appear depressed, growth slows (Engeland, 1991).

Why it works: Garlic has a shallow root system that cannot draw moisture from deep soil layers. In hot, dry weather, the plant intensively evaporates water through its leaves (transpiration). If water uptake from the soil is insufficient, the plant starts to conserve water. The tips of the leaves are the first to suffer – these are the most distant parts from the roots, receiving water last. Tip tissues die from dehydration (Brewster, 2008).

What to do: Normalize watering. Garlic requires regular but moderate watering during active growth (spring – early summer). An optimal schedule is 1-2 deep waterings per week to moisten the soil to a depth of 20-30 cm. In hot weather, increase frequency. Water in the morning or evening to avoid sunburn. Stop watering 2-3 weeks before harvest for better bulb maturation and storage (UMN Extension, 2024).

Salt Stress (Soil Salinization)

Symptoms: Leaf tips dry out and turn brown, as if burned. A brown border may appear along the leaf edges. Leaves may curl and deform. Plants appear depressed, and growth slows. This symptom often appears after applying large amounts of mineral fertilizers or watering with hard water (Engeland, 1991).

Why it works: Excess salts in the soil (especially sodium, chlorine, and others) create high osmotic pressure in the soil solution. Garlic roots cannot absorb water from such a solution because the osmotic pressure inside root cells is lower than in the soil. This creates so-called "physiological drought" – the plant suffers from lack of moisture even if the soil is wet. Salts accumulate in leaf tips, causing burns and tissue death (Brewster, 2008).

What to do: Avoid excessive application of mineral fertilizers, especially those containing chlorine (e.g., potassium chloride). Use soft water for irrigation (rainwater, settled water). When signs of salinization appear, heavy watering to leach the soil (remove excess salts) can be helpful. Adding organic matter (compost, well-rotted manure) also helps reduce salt stress by improving soil structure and buffering capacity (Brewster, 2008).

Potassium Deficiency

Symptoms: Leaf tips dry out and become brown, as if burned. A yellow-brown border ("marginal burn") appears along the leaf edges. The leaf blade may become crinkled. Symptoms appear first on older, lower leaves, then spread upwards. Plant growth slows, and bulbs are small (Brewster, 2008).

Why it works: Potassium is involved in regulating plant water balance, maintaining cell turgor, and opening and closing stomata. When deficient, water transport to leaf tips and edges is disrupted, causing them to die. Potassium is also important for carbohydrate synthesis and their transport to the bulb, so its deficiency directly affects yield (Engeland, 1991).

What to do: Apply a potassium fertilizer. For organic gardening, wood ash (which contains potassium in a available form) is suitable, applied either dry (during digging) or as an infusion. Among mineral fertilizers, use potassium sulfate (sulphate of potash) as it does not contain chlorine and does not cause burns. Potassium chloride is not recommended for garlic (Brewster, 2008).

Root Problems (Physiological)

Symptoms: Leaf tips dry out, leaves may turn yellow or pale, lose turgor. When pulled out, roots are weak, darkened, rotting, or mechanically damaged. This can result from waterlogging, soil compaction, damage during cultivation, or soil pest activity (Brewster, 2008).

Why it works: Roots are the main organs for absorbing water and nutrients. If the root system is weakened or damaged, the plant cannot supply itself with water and nutrients, even if they are present in the soil. As a result, the most distant parts from the roots – the leaf tips – suffer first. This is similar to drought symptoms, but the cause is not a lack of moisture in the soil, but the roots' inability to absorb it (Engeland, 1991).

What to do: Identify and eliminate the cause of root damage. If it's waterlogging – normalize watering and improve drainage. If it's soil compaction – deep cultivate between rows. If it's pests – apply appropriate control measures. To stimulate root growth, use preparations based on humic acids or phosphorus-potassium fertilizers, which promote root system development (Brewster, 2008).

How to Distinguish Causes of Tip Drying?

For quick diagnosis, use the following approach:

It's important to remember that in reality, symptoms often combine. For example, in waterlogged soil, roots suffer, manifesting as tip drying against a background of leaf yellowing. Therefore, always assess the plant's condition as a whole.

Stem Nematode (Ditylenchus dipsaci)

Symptoms: Leaves curl, deform, thicken, become crinkled or wavy. Blisters and yellowish spots may appear on them. Plants are severely stunted, appearing dwarfed. Upon examining the bulb, cracks on the outer skins may be found, the base may be softened, and roots rotting. This damage often appears as focal patches in the field – groups of plants growing close together (Brewster, 2008; Engeland, 1991).

Why it works: The nematode penetrates leaf and stem tissues through stomata or mechanical damage. Feeding on cell sap, it secretes enzymes that break down cell walls and cause tissue proliferation (hypertrophy). As a result, leaves deform, curl, and their normal growth is disrupted. Additionally, the nematode vectors bacterial infections, worsening the damage (Brewster, 2008).

What to do: Unfortunately, there are no effective treatments for nematode infestation on garlic. The main strategy is prevention: use only healthy planting material from reliable sources, heat-treat cloves before planting in hot water (45°C for 2-3 hours) to kill nematodes. When infested plants are found, remove and burn them immediately. Practice strict crop rotation – do not return onions or garlic to an infested plot for at least 4-5 years (Brewster, 2008).

Viral Infections (Onion Yellow Dwarf Virus (OYDV), Leek Yellow Stripe Virus (LYSV), and others)

Symptoms: Leaves curl, become crinkled, may twist into a spiral or ring. Yellow stripes, streaks, or a mosaic pattern appear on the leaf blades. Plants are stunted, appear depressed. Bulbs are small, loose, and often deformed (Brewster, 2008; Walkey, 1990).

Why it works: Viruses are submicroscopic pathogens that enter plant cells and reprogram their metabolism for their own replication. This causes disruption of chlorophyll synthesis, tissue deformation, and overall growth depression. Viruses are often transmitted through infected planting material or carried by insect vectors such as aphids and thrips (Brewster, 2008).

What to do: As with nematodes, treatment for viral diseases is impossible. The primary control method is prevention: use only healthy, certified virus-free planting material. Growing garlic from healthy cloves (elite or first-generation) is the best defense. Remove and destroy plants showing virus symptoms. Control insect vectors (aphids, thrips) by treating plantings with insecticides or using biological products (Brewster, 2008).

Physiological Stress (Drought, Salt Stress, Herbicide Stress)

Symptoms: Curling can vary – leaves may roll into a tube, curl in a spiral, or fold along the central vein. Leaves often dry or yellow at the edges, becoming brittle. Symptoms appear more uniformly across the field, unlike the focal damage of nematodes or viruses (Engeland, 1991).

Why it works: During moisture deficiency or salt stress, the plant reduces leaf surface area to decrease evaporation. Curling is a protective reaction to reduce the evaporating surface. Herbicide stress causes hormonal imbalances, leading to abnormal cell growth and leaf deformation (Brewster, 2008; Engeland, 1991).

What to do: The symptom itself is non-specific. Assess the overall condition of the planting. If curling is accompanied by general wilting and dry soil – improve watering. If fertilizers or herbicides were recently applied – it might be salt or chemical burn. In that case, conduct heavy watering to reduce salt concentration in the soil. In the future, strictly follow fertilizer and herbicide dosages and apply them only within recommended periods (Engeland, 1991).

Root Damage

Symptoms: Leaves curl, lose turgor, may wilt. When pulled out, a weak, damaged, or rotting root system is found. Symptoms often combine with yellowing or whitening of leaves (Brewster, 2008).

Why it works: Root damage disrupts water and nutrient supply to the above-ground part. Curling here is a reaction to water deficit, similar to drought. Causes of root damage include waterlogging, soil compaction, deep cultivation, or soil pest activity (Brewster, 2008).

What to do: Cultivate carefully to avoid root damage. Normalize watering, improve drainage on heavy soils. If pests are found, apply appropriate control measures. To stimulate root growth, use root feeding with phosphorus and potassium, as well as rooting agents (Brewster, 2008).

How to Distinguish Causes of Leaf Curling?

Use a comprehensive approach:

Important Note: Leaf curling is a complex symptom, and its cause often requires laboratory confirmation. For example, symptoms of nematodes and viruses can be very similar. In doubtful cases, it is recommended to send samples to a diagnostic laboratory for accurate pathogen identification (Brewster, 2008).

Waterlogging and Stagnant Water

Symptoms: Plants appear depressed, leaves lose turgor, become limp, and turn yellow starting from the lower ones. Growth slows or stops completely. Upon digging, roots are dark, brown or black, slimy, with a putrid odor. The root system is weak and easily separates from the base. Green moss or algae may appear on the soil surface (Brewster, 2008).

Why it works: Garlic is sensitive to waterlogging. In water-filled soil pores, oxygen levels drop sharply. Roots, suffering from oxygen deprivation, switch to anaerobic respiration, producing toxic substances (ethanol, acetic acid). Root cells die, and roots begin to rot. In such conditions, pathogenic fungi (species of Pythium, Fusarium) are activated and quickly colonize weakened tissues (Brewster, 2008).

What to do: Normalize the water regime. Water garlic only when the topsoil layer dries out. Stop watering entirely during rainy periods. If the soil is heavy clay, improve its structure: add sand, well-rotted compost, or peat during planting or in autumn. Consider planting on raised beds to ensure drainage. Planting garlic in areas with high groundwater levels is not recommended (Engeland, 1991).

Fungal Diseases of Roots and Base

Symptoms: Leaves turn yellow, wilt, and sometimes tips dry out. Plant growth slows. Upon pulling out, characteristic signs of a specific disease are found:

Fusarium (Fusarium Basal Rot, Fusarium oxysporum f.sp. cepae). Roots and the base turn brown and rot. A white, pink, or yellowish-brown mycelial coating appears on the base. The bulb becomes soft and watery. A pinkish coating may be visible between the cloves. The disease often manifests in hot weather (Brewster, 2008; Entwistle, 1990).

White Rot (Sclerotium cepivorum). Roots and the base are covered with a white, fluffy mycelial coating. Small (about 0.5 mm) black sclerotia – round structures resembling poppy seeds – appear on it. Leaves turn yellow and die, starting from the tips. The plant is easily pulled from the soil. A very dangerous disease, as sclerotia can persist in the soil for up to 10 years (Entwistle, 1990).

Pink Rot (Pyrenochaeta terrestris). Roots take on a pink or pinkish-purple hue, then turn brown and die. The above-ground part turns yellow and is stunted. The disease often appears in the second half of the growing season in hot weather (Brewster, 2008).

Why it works: Fungal pathogens enter the root system through mechanical damage, weakened tissue areas, or natural openings. They destroy cell walls, clog vessels, and secrete toxins, leading to root death and ultimately the whole plant (Brewster, 2008).

What to do: Prevention is the main control method:

• Use healthy planting material (Engeland, 1991).
• Practice crop rotation (do not return garlic or onions to the same spot for at least 3-4 years, and 5-6 years for White Rot) (Brewster, 2008).
• Apply biological products based on antagonistic fungi (Trichoderma spp.) and bacteria (Bacillus subtilis) to the soil (Brewster, 2008).
• Immediately remove and burn diseased plants (Brewster, 2008).
• Lime acidic soils, as many fungi prefer an acidic environment (Engeland, 1991).

Stem Nematode (Ditylenchus dipsaci)

Symptoms: Roots are weak, often rot, and blisters and thickenings may be visible on them. The bulb base becomes loose and may crack. Plants are stunted, leaves yellow, curl, and deform. Damage is often focal (Brewster, 2008).

Why it works: The nematode is a microscopic worm that penetrates root, stem, and leaf tissues. It feeds on cell sap, destroying cells. The enzymes it secretes cause tissue hypertrophy (blisters, thickenings) and disrupt water and nutrient transport (Brewster, 2008).

What to do: No treatment is possible. Prevention:

• Heat-treat cloves before planting in hot water (45°C for 2-3 hours) (Brewster, 2008).
• Use only healthy planting material from reliable sources.
• Remove and burn infested plants.
• Practice crop rotation for at least 4-5 years (Brewster, 2008).

Soil Compaction

Symptoms: Plants are stunted, leaves turn yellow, may wilt. Roots upon digging are weak, poorly branched, often distorted. The soil around the roots is dense, poorly permeable to air and water. Often observed after heavy rains, prolonged absence of cultivation, or on plots with disturbed soil structure (Engeland, 1991).

Why it works: In compacted soil, oxygen content decreases, drainage worsens, and roots cannot penetrate deeply. They grow superficially in the top layer, which dries out faster, making the plant more vulnerable to stress. Dense soil creates a mechanical barrier for root growth (Brewster, 2008).

What to do: Regularly cultivate between rows, but do it carefully to avoid damaging the shallow roots. Deep cultivation (8-10 cm) before planting garlic improves aeration and soil structure. Add organic matter (compost, humus), which makes the soil looser and more air-permeable (Engeland, 1991).

How to Distinguish Causes of Root Weakening?

Important Note: Root problems are often interconnected. For example, waterlogging weakens roots, making them susceptible to fungal infection. Conversely, root damage by nematodes makes fungal infection easier. So, during inspection, always assess the condition of the soil, roots, and the above-ground part as a whole.

Poor Planting Material

Symptoms: Season after season, bulbs get smaller, even with good cultivation practices. Bulbs often have an irregular shape, are loose, with many small, uneven cloves. Plants may look healthy, but the harvest is disappointing (Engeland, 1991).

Why it works: The size of the future bulb directly depends on the size of the planted clove. Large cloves contain more stored nutrients needed for a rapid start and forming a robust plant. If you use small cloves or cloves from small, degenerating bulbs, the plant is weakened from the start. Studies show that the weight and size of the planting bulb affect yield size even more than the weight of the individual clove (Engeland, 1991). Using cloves from bulbs with many cloves (more than 10) can also reduce yield (Engeland, 1991).

What to do: For planting, select only the largest, healthiest cloves from large, firm bulbs. The ideal clove weight for planting is 6–9 grams (Engeland, 1991). Do not use cloves from bulbs that are damaged, show signs of rot, or from very small bulbs (less than 2 inches in diameter for winter varieties). For planting, it's best to take cloves from the outer row – they are larger. Regularly renew planting material by purchasing elite bulbs from reputable producers to avoid variety degeneration (Engeland, 1991).

Dense Planting

Symptoms: Plants appear healthy, but bulbs are small, often elongated or irregularly shaped. Leaves may be paler than usual, plants stretch, competing for light. Bulbs may feel loose (Engeland, 1991; UMN Extension, 2024).

Why it works: Garlic is a crop demanding adequate growing space. With dense planting, plants compete for light, water, and nutrients. The root systems of neighboring plants intertwine and hinder each other. As a result, each plant receives insufficient resources to form a large bulb. The optimal distance between cloves in a row is 5–8 cm, and between rows 18–30 cm (Engeland, 1991; UMN Extension, 2024). To achieve large bulbs (2.5 inches and more), spacing between cloves should be at least 5–8 cm (Engeland, 1991).

What to do: Follow the recommended planting scheme. For winter varieties, planting cloves 10–15 cm apart in the row and 25–30 cm between rows is optimal. For very large bulbs, increase the distance to 15–20 cm between cloves. Don't save space – it's better to plant fewer plants but get a quality, large harvest (Engeland, 1991).

Nutrient Deficiency

Symptoms: Plants are pale, weak, leaves are small, yellow prematurely. Growth is slow, bulbs are small, often with thin outer skins. Symptoms may appear unevenly, especially on poor soils or in years with unfavorable weather (Brewster, 2008; Engeland, 1991).

Why it works: Garlic is a relatively demanding crop nutritionally. To form a large bulb, it needs nitrogen (for leaf growth), phosphorus (for root development and maturation), and potassium (for accumulating carbohydrates in the bulb). A deficiency of any of these, especially nitrogen and potassium, directly affects yield size. Garlic also needs soil organic matter – on fertile, humus-rich soils, bulbs are larger and denser (Engeland, 1991; Brewster, 2008).

What to do: Conduct a soil test or apply a complete fertilizer before planting. Application of 1–2 pounds (0.45–0.9 kg) of a complete fertilizer (e.g., 10-10-10) per 100 square feet (about 9.3 m²) before planting is recommended (Engeland, 1991). In spring, 3–4 weeks after emergence, apply a nitrogen side-dressing (e.g., 1 pound (0.45 kg) of ammonium nitrate per 100-foot row) (Engeland, 1991). Add organic matter – well-rotted manure or compost 2–3 months before planting. This will improve soil structure and provide plants with nutrients throughout the growing period (Engeland, 1991; UMN Extension, 2024).

Lack of Light

Symptoms: Plants are elongated, pale, with thin, long leaves. Bulbs are small, often elongated or deformed. This is especially noticeable in areas shaded by trees, buildings, or neighboring tall crops (Engeland, 1991).

Why it works: Garlic is a sun-loving plant. For normal growth and large bulb formation, it needs at least 6-8 hours of direct sunlight per day. In shade, photosynthesis is less intensive, the plant accumulates fewer carbohydrates needed for bulb growth. This is one of the most common causes of small yields for novice gardeners (Engeland, 1991).

What to do: Choose the sunniest plots for garlic. Do not plant it near tall crops (sunflowers, corn, tall tomatoes) or in the shade of buildings. Orient beds north-south to ensure even lighting throughout the day (Engeland, 1991).

Too Early or Too Late Planting (Especially for Winter Varieties)

Symptoms: When planted too early, winter garlic plants may go into winter with excessive greenery, weakening them and reducing yield. When planted too late, garlic does not have time to root before frost, sprouts weakly in spring, plants are small, and bulbs are small (Engeland, 1991; UMN Extension, 2024).

Why it works: Winter garlic needs 4-6 weeks to root before severe frosts. Planting too early leads to excessive green growth in autumn, depleting the clove. Planting too late – roots don't develop, the plant weakens over winter, and spends energy on recovery in spring instead of growth (Engeland, 1991).

What to do: Plant winter garlic 4-6 weeks before the onset of sustained frosts. In temperate climates, this is usually October – early November. For spring garlic, plant as early as possible in spring, as soon as the soil allows, so it can build vegetative mass before hot weather arrives (Engeland, 1991; UMN Extension, 2024).

How to Distinguish Causes of Small Bulbs?

Important Note: Often the cause of a small bulb is complex. For example, on poor soil with dense planting and lack of light, the yield will be very small. Therefore, always evaluate all factors affecting garlic growth and try to create optimal conditions from the start.

Natural Senescence and Over-maturation

Symptoms: The bulb becomes loose, outer skins thin, becoming papery. Cloves separate easily, with gaps visible between them. The bulb may appear "bloomed," resembling an open flower. This is often observed with delayed harvest when the plant has already completed its cycle (Engeland, 1991).

Why it works: Garlic has a natural development cycle. When the bulb is fully mature, cloves are no longer tightly pressed together, and the outer skins begin to dry and thin. If garlic is left in the ground longer than the optimal time, this process goes too far: cloves "open up," the bulb loses firmness and becomes loose. This is especially characteristic of winter garlic varieties (Engeland, 1991).

What to do: Harvest on time. The optimal harvest time is when the lower leaves begin to yellow and dry, while the upper leaves (5-6 of them) are still green (Engeland, 1991; UMN Extension, 2024). To check, dig up a few sample bulbs and cut them in half: if the cloves are fully formed and fill the head tightly – it's time to harvest (UMN Extension, 2024). Do not wait for complete lodging and drying of leaves – this often leads to over-maturation and looseness.

Potassium Deficiency

Symptoms: Bulbs are loose, cloves small, not tightly packed. Outer skins are thin, may be damaged. Leaves often yellow at the edges and dry, starting from the tips. Plant growth is slow. Symptoms appear first on older, lower leaves, then spread upwards (Brewster, 2008).

Why it works: Potassium is a key element for forming a dense bulb structure. It participates in carbohydrate synthesis, which accumulates in cloves, and in water balance regulation, affecting tissue firmness. When deficient, carbohydrate transport from leaves to the bulb is disrupted, cloves don't gain mass, and the bulb remains loose. Potassium deficiency is especially common in the second half of the growing season when active bulb formation occurs (Brewster, 2008).

What to do: Apply a potassium fertilizer. The best option for garlic is potassium sulfate (sulphate of potash) as it is chlorine-free. Wood ash is also an excellent source of potassium. Apply ash dry (1 cup per 1 m²) or as an infusion (1 liter ash per 10 liters water, steep for 3-4 days, apply 1 liter per plant). Fertilize during active bulb growth (2-3 weeks before harvest) (Brewster, 2008).

Stem Nematode (Ditylenchus dipsaci)

Symptoms: The bulb is loose, deformed. Outer skins may crack, cloves have irregular shapes, often with brown or gray spots. On a cut bulb, blisters and loosening of tissues are visible. Plants are stunted, leaves curled, deformed, yellow (Brewster, 2008; Engeland, 1991).

Why it works: The nematode, penetrating bulb tissues, feeds on cell sap and destroys cell walls. The enzymes it secretes cause tissue proliferation and loosening, leading to clove deformation and loss of bulb density. Affected tissues often become a breeding ground for bacteria and fungi, worsening the problem (Brewster, 2008).

What to do: There are no effective treatments for nematode infestation on garlic. The main strategy is prevention: use only healthy planting material, heat-treat cloves before planting in hot water (45°C for 2-3 hours), practice crop rotation for at least 4-5 years. Remove and burn affected plants immediately (Brewster, 2008).

Damage during Harvest and Handling

Symptoms: The bulb becomes loose after harvest, especially during long-term storage. Cloves separate from the base, outer skins are damaged. This is often accompanied by cracks on the bulb (Engeland, 1991).

Why it works: Mechanical damage during digging, cleaning, transport, or sharp impacts breaks the integrity of the outer skins and the base. This causes cloves to lose connection with the base, and the bulb falls apart. Bulbs with thinned outer skins are especially vulnerable (Engeland, 1991).

What to do: Dig garlic carefully, especially if the soil is compact or dry. Use a fork or spade, lifting bulbs from below. Do not pull garlic by the stems, as this can damage the neck and base. Clean bulbs from soil by hand, do not knock them against each other. Dry garlic in a well-ventilated place, then carefully trim stems and roots, leaving 1-2 cm (Engeland, 1991).

Excess Nitrogen

Symptoms: Leaves are large, dark green, succulent, excessively developed. Bulbs are loose, cloves not tightly packed. Often delayed maturation and reduced storage life are observed (Engeland, 1991; Brewster, 2008).

Why it works: Excess nitrogen stimulates green mass growth at the expense of bulb formation. The plant accumulates excessive moisture in tissues, making them loose. Furthermore, nitrogen delays maturation and worsens clove quality. Applying nitrogen fertilizers in large amounts during the second half of the growing season is particularly dangerous (Engeland, 1991).

What to do: Do not exceed recommended nitrogen fertilizer rates. In spring, during active leaf growth, fertilize garlic with nitrogen (1-2 times). After bulb formation begins (second half of June), stop nitrogen fertilization and switch to potassium-phosphorus fertilizers. Use complete fertilizers with reduced nitrogen content (e.g., 0-10-10 or 5-10-15) (Engeland, 1991).

How to Distinguish Causes of Loose Bulbs?

Important Note: Bulb looseness can be a complex problem. For example, on waterlogged soils (especially with excess nitrogen), bulbs often end up loose and store poorly. Therefore, always assess the condition of the soil, planting material, and overall agricultural practices.

Natural Development from Bulbils (Aerial Bulblets)

Symptoms: Plants grown from planted bulbils (aerial bulblets) produce a single, solid bulb – a round. This is especially characteristic of the first year of growing from bulbils. Plants may appear healthy, leaves develop normally, but the bulb remains solid (Engeland, 1991).

Why it works: Bulbils are small daughter bulbs formed in the inflorescence of bolting garlic varieties. Due to their small size, they contain very little stored nutrients. In the first year after planting, the plant does not accumulate enough energy to divide into cloves, so it forms a solid bulb – a round. This is a normal, physiological process. The following year, this round will grow into a full head divided into cloves (Engeland, 1991).

What to do: If you are growing garlic from bulbils, a round is the expected result. This is a good way to renew planting material and avoid disease accumulation. Harvest the rounds, dry them, and use them for planting next year. It takes two years to get a full bulb with cloves (Engeland, 1991).

Incorrect Planting Material (Small Cloves)

Symptoms: Small cloves planted produce small rounds or bulbs with poorly formed, indistinct cloves. Plants may be weak, with small leaves. The harvest is disappointing (Engeland, 1991).

Why it works: As mentioned in Chapter 7, the size of the planted clove directly affects the size of the future bulb. If the planting material is very small, the plant simply doesn't have enough energy to form a bulb divided into cloves. As a result, a small monolithic bulb forms (Engeland, 1991).

What to do: Always use only large, healthy cloves from well-formed bulbs (weighing 6-9 g) for planting. If you have many small cloves, you can plant them separately for greens or use them to produce rounds, which can then be planted the next year for a full harvest (Engeland, 1991).

Variety Degeneration (Genetic Degradation)

Symptoms: Bulbs become small, irregularly shaped, often fail to divide into cloves or form ugly, fused cloves. Plants are weak, may yellow prematurely. Yields decline year after year (Engeland, 1991).

Why it works: Garlic is a vegetatively propagated crop (by cloves). With many years of using the same planting material without renewal, viruses, fungal infections, and other pathogens accumulate, leading to variety degeneration. This manifests in smaller bulbs, loss of division ability, and reduced yields (Engeland, 1991; Brewster, 2008).

What to do: Regularly renew planting material. Purchase elite bulbs from reputable producers every 3-5 years. Practice growing garlic from bulbils – this is an effective way to rejuvenate a variety, as bulbils do not accumulate viruses (Engeland, 1991).

Viral Infections

Symptoms: Bulbs do not divide into cloves or form ugly, deformed, fused cloves. Plants are stunted, leaves may have yellow stripes, streaks, mosaic patterns, or curl. Sometimes plant dwarfism is observed (Brewster, 2008; Walkey, 1990).

Why it works: Some viruses affecting garlic can disrupt cell division and tissue differentiation processes in the bulb. As a result, a non-structured, fused bulb or a bulb with underdeveloped cloves forms instead of a full head. Viruses are often transmitted through planting material and insect vectors (aphids, thrips) (Brewster, 2008).

What to do: Treatment for viral diseases is impossible. The main control method is prevention: use only healthy, certified virus-free planting material. Remove and destroy plants with suspicious symptoms. Control insect vectors (aphids, thrips) (Brewster, 2008).

Excess Nitrogen and Waterlogging

Symptoms: Leaves are large, dark green, succulent, excessively developed. Bulbs are loose or, conversely, solid but soft, watery. Often delayed maturation and reduced storage life are observed (Engeland, 1991).

Why it works: Excess nitrogen and excessive moisture stimulate vegetative growth at the expense of bulb formation. Instead of accumulating carbohydrates in cloves, the plant continues to grow, and the division into cloves either does not start or proceeds incorrectly. As a result, the bulb may remain solid or form ugly cloves (Engeland, 1991).

What to do: Strictly follow the fertilization regime. Apply nitrogen fertilizers only in the first half of the growing season (before bulb formation starts), using moderate doses. In the second half, switch to phosphorus-potassium fertilizers. Normalize watering – garlic should not suffer from waterlogging (Engeland, 1991).

How to Distinguish Causes of an Undivided Bulb?

Important Note: In most cases, a single monolithic bulb is a physiological round that serves as a transitional stage to forming a full head. If you are unsure of the cause, try to divide the problem into two classes: (1) round as an expected result (bulbils, small cloves) and (2) round as a pathology (viruses, degeneration, agronomic errors). In the latter case, take measures to improve planting material health and care.

White Rot (Sclerotium cepivorum)

Symptoms: The bulb is covered with a white, fluffy, cottony mycelial coating. Small (about 0.5 mm) black, round structures – sclerotia, resembling poppy seeds – appear on the coating surface. Roots and the base rot, the plant is easily pulled from the soil. Leaves turn yellow and die, starting from the tips. The rot smell is fungal, earthy. The disease often appears in patches (Entwistle, 1990; Brewster, 2008).

Why it works: The causal agent of White Rot is a soil-borne fungus that enters the roots and bulb base through mechanical damage or natural openings. The fungus secretes enzymes that break down cell walls and toxins causing tissue death. The white coating is the fungal mycelium, and the black sclerotia are resting structures that can survive in soil for up to 10 years or more (Entwistle, 1990).

What to do: There are no effective treatments for White Rot. The main strategy is prevention:

• Use only healthy, certified planting material (Brewster, 2008).
• Practice strict crop rotation – do not return garlic or onions to an infested plot for at least 5-6 years (Entwistle, 1990).
• When infection foci are found, immediately remove and burn affected plants together with the surrounding soil clod (Entwistle, 1990).
• Apply biological products based on Trichoderma spp. (antagonistic fungi) and Bacillus subtilis (bacteria) to the soil (Brewster, 2008).
• In some regions, soil liming is used to reduce acidity (the fungus prefers acidic soils) (Entwistle, 1990).

Fusarium Basal Rot (Fusarium oxysporum f.sp. cepae)

Symptoms: The bulb softens, becomes watery. A white, pink, or yellowish-brown mycelial coating appears on the base. Roots rot, turning brown or black. A pinkish or reddish coating may be visible between the bulb scales. Leaves turn yellow from the tips, wilt. The disease often manifests in hot weather, in the second half of the growing season (Brewster, 2008; Entwistle, 1990).

Why it works: The fungus Fusarium penetrates roots and the base through mechanical damage or weakened tissues. It clogs the plant's vascular system, disrupting water and nutrient transport, and secretes toxins causing tissue rot. The fungus is active at high soil temperatures (>25°C) and in waterlogged soils (Brewster, 2008).

What to do: Prevention is the best treatment:

• Use healthy planting material (Brewster, 2008).
• Practice crop rotation (do not return garlic to the same spot for at least 3-4 years) (Brewster, 2008).
• If diseased plants are found, remove and burn them (Brewster, 2008).
• Apply biological products based on Trichoderma spp. or Bacillus subtilis to the soil (Brewster, 2008).
• Optimize watering – avoid waterlogging (Brewster, 2008).

Bacterial Rot (Soft Rot, Bacteriosis)

Symptoms: The bulb softens, becomes slimy, watery. Tissues turn yellowish or brown, emitting a foul, putrid odor. A cloudy liquid may exude between the scales. Rot often starts at the neck or at a point of mechanical injury. Affected bulbs quickly disintegrate (Brewster, 2008).

Why it works: Bacteria (species of Erwinia, Pantoea, Pseudomonas, and others) enter bulb tissues through mechanical damage, cracks, or weakened tissues. They secrete pectolytic enzymes that break down cell walls, turning tissues into a soft, watery mass. Bacterial rots often develop in warm, humid weather and especially actively when the integrity of the outer skins is compromised (Brewster, 2008).

What to do: Prevention:

• Avoid mechanical damage during harvest and handling (Brewster, 2008).
• Dry garlic thoroughly before storage (Brewster, 2008).
• Store garlic at low humidity (65-70%) and with good ventilation (Brewster, 2008).
• Avoid soil waterlogging during the maturation period (Brewster, 2008).
• Remove infected bulbs immediately from storage to prevent spread (Brewster, 2008).

Waterlogging and Stagnant Water

Symptoms: The bulb becomes soft, watery, without a characteristic rot smell or with a faint smell. Tissues may be pale, slightly translucent. Rot often starts from the base or outside the bulb. When digging up such bulbs, the soil around may be wet with an unpleasant odor (Brewster, 2008).

Why it works: In waterlogged soil, garlic roots suffer oxygen deprivation and die. Dead roots and tissues become a breeding ground for various saprophytic fungi and bacteria, causing secondary rot. Additionally, prolonged immersion in water leads to tissue softening, making it easier for pathogens to penetrate (Brewster, 2008).

What to do: Normalize watering. Do not water garlic during rainy periods. If the soil is heavy clay, improve drainage (add sand, compost, create raised beds). In case of waterlogging, perform deep cultivation between rows to improve aeration. Remove and dry affected bulbs (Brewster, 2008).

Damage during Harvest and Improper Storage

Symptoms: Rot develops at the site of mechanical damage (cracks, cuts, bruises). The bulb rots locally, starting from the damaged area. With high humidity in storage, rot spreads quickly to neighboring bulbs (Engeland, 1991; Brewster, 2008).

Why it works: Mechanical damage breaches the integrity of the outer skins, which protect the bulb from microorganism entry. Bacteria and fungi enter the tissues through cracks and cuts, causing rot. In conditions of high humidity and poor ventilation, rot develops especially quickly (Brewster, 2008).

What to do: Dig garlic carefully, avoiding bulb damage. Do not knock bulbs against each other when cleaning soil. Dry garlic thoroughly before storage. Store in a dry, well-ventilated place at 0-4°C (for long-term storage) or at room temperature (up to 3-4 months) (Engeland, 1991). Optimal storage humidity is 65-70% (Brewster, 2008). Regularly inspect stored garlic and remove affected bulbs (Brewster, 2008).

How to Distinguish Causes of Bulb Rotting?

Important Note: Bulb rotting is always a serious problem requiring immediate action. In most cases, treating affected plants is impossible – they must be removed and destroyed. The key is to prevent infection from spreading to healthy plants. To do this, strictly follow crop rotation, use healthy planting material, ensure good drainage, and maintain optimal storage conditions. Remember: prevention is always more effective than cure (Entwistle, 1990; Brewster, 2008).

Incorrect Planting Depth

Symptoms: Sprouts appear later than expected, they are weak, with distorted leaves. Many cloves do not sprout at all. Upon digging, cloves are either buried too deep or, conversely, sitting on the surface or in a dry soil layer (Engeland, 1991; UMN Extension, 2024).

Why it works: Planting depth directly affects the sprout's ability to reach the surface. If planted too shallow (less than 2-3 cm), cloves may suffer from drying out, freezing, or be pushed to the surface by frost heaving. If planted too deep (more than 6-8 cm), the sprout lacks the strength to break through the soil thickness, especially if the soil is compact or heavy. The optimal depth for winter garlic is 3-5 cm from the clove base to the surface, and for spring garlic 2-3 cm (Engeland, 1991; UMN Extension, 2024).

What to do: Follow the recommended planting depth. For winter varieties – 4-6 cm (from the clove top to the soil surface) (UMN Extension, 2024). For spring varieties – 2-3 cm. If using mulch, consider its thickness – the total covering depth (including mulch) should not exceed 6-7 cm. On heavy clay soils, reduce depth; on light, sandy soils, increase it (Engeland, 1991).

Too Small or Low-Quality Planting Material

Symptoms: Sprouts appear weak, with thin, pale leaves. Some cloves do not germinate. Upon digging, small, shriveled, or rotting cloves are found (Engeland, 1991).

Why it works: Small cloves contain fewer stored nutrients. They lack the energy to form a robust sprout and overcome soil resistance. Moreover, small cloves are more often diseased or damaged (Engeland, 1991).

What to do: For planting, select only large, healthy cloves (weighing at least 5-6 g). Discard cloves showing signs of disease, damage, dryness, or shriveling. Before planting, calibrate planting material, separating large and small cloves, and plant them separately (Engeland, 1991).

Incorrect Planting Time (Winter Garlic)

Symptoms: If planted too early, winter garlic sprouts in autumn and goes into winter with developed green mass, often leading to freezing or weakening in spring. If planted too late, cloves do not root before frost, and spring sprouts appear late, weak, or not at all (Engeland, 1991; UMN Extension, 2024).

Why it works: Winter garlic needs 4-6 weeks to root at soil temperatures around +5…+10°C. Planting too early leads to excessive leaf growth, depleting the clove and reducing winter hardiness. Planting too late – roots don't develop, the plant enters winter weakened, and cannot start growing normally in spring (Engeland, 1991).

What to do: Plant winter garlic 4-6 weeks before the onset of sustained frosts. In temperate climates, this is usually the second half of September – first half of October (Engeland, 1991; UMN Extension, 2024). Use the average daily temperature as a guide: when it stabilizes around +10°C, it's time to plant. Don't delay planting, but don't rush either.

Incorrect Watering Regime

Symptoms: Sprouts are sparse, uneven. Upon digging, cloves are found either in dry soil or waterlogged and rotting (Engeland, 1991; Brewster, 2008).

Why it works: Garlic needs moist, but not wet, soil for rooting. With a lack of moisture, roots don't develop, and the clove dries out. With waterlogging, the clove rots or is affected by fungal diseases (Brewster, 2008).

What to do: After planting winter garlic, if autumn is dry, water once or twice for good rooting. Then stop watering to prevent active growth before winter. In spring, if winter was low in snow and the soil is dry, light watering can stimulate growth. Spring garlic is watered regularly until sprouts appear, but avoid waterlogging (Engeland, 1991).

Disease or Pest Infestation

Symptoms: Sprouts are absent or appear very rarely. Upon digging, cloves show signs of rot (white, pink, black coating), are damaged by nematode (blisters, cracks), or eaten by pest larvae (onion fly, wireworm) (Brewster, 2008; Engeland, 1991).

Why it works: Fungal pathogens (White Rot, Fusarium, Penicillium) can destroy the clove before sprouting. Stem nematode sucks sap and destroys tissues. Onion fly and other pests damage cloves (Brewster, 2008).

What to do: Prevention:

• Use only healthy planting material (Engeland, 1991).
• Before planting, heat-treat cloves in hot water (45°C, 2 hours) to kill nematodes and some fungi (Brewster, 2008).
• Practice crop rotation (Brewster, 2008).
• Apply biological products (Trichoderma, Bacillus subtilis) for protection against fungal diseases (Brewster, 2008).
• If pests are found, use approved insecticides or traps (Brewster, 2008).

Improper Storage of Planting Material

Symptoms: Sprouts are weak, cloves do not germinate. Upon digging, dry, shriveled or, conversely, rotting cloves are found (Engeland, 1991).

Why it works: Storing cloves at incorrect temperatures (below 0°C or above 25°C) or at high humidity can disrupt growth processes. Too high a temperature promotes premature sprouting or disease development. Too low a temperature damages tissues (Engeland, 1991).

What to do: Store garlic planting material in a cool, dry place with good ventilation (at 15-20°C for spring garlic and 0-5°C for winter garlic, but check specific variety recommendations). Optimal humidity is 65-70% (Brewster, 2008). 1-2 weeks before planting, move cloves to a warmer place (spring garlic – to stimulate sprouting, winter – for acclimatization) (Engeland, 1991).

How to Distinguish Causes of Poor Germination?

Important Note: If 2-3 weeks have passed after planting winter garlic and there are no sprouts, but the cloves look healthy when dug up – they might simply be dormant and will appear in spring after the soil warms. However, if you find rot or damage upon digging, it's a cause for concern (Engeland, 1991).

Incorrect Planting Time (Too Early or Too Late)

Symptoms: When planted too early, plants actively develop in autumn, forming a large green mass (10-15 cm or more). In winter, such plants often freeze or are damaged by frost, emerging weakened in spring. When planted too late, garlic does not root before frost, spring sprouts appear late, weak, or absent (Engeland, 1991; UMN Extension, 2024).

Why it works: Winter garlic needs 4-6 weeks to form a robust root system at soil temperatures around +5…+10°C, but it should not start active above-ground growth. The optimal plant size for winter is 5-8 cm of green mass. Planting too early causes the plant to expend clove nutrients on leaf growth, depleting itself and losing frost resistance. Planting too late – roots don't develop, and the plant cannot withstand frost heaving and freezing (Engeland, 1991).

What to do: Plant winter garlic 4-6 weeks before the onset of sustained frosts. Use the average daily temperature as a guide: when it stabilizes in the range of +8…+12°C, the optimal planting time has arrived (Engeland, 1991). In most temperate regions, this is late September – mid-October, but dates vary by climate zone.

Insufficient Variety Frost Hardiness

Symptoms: In severe winters, plants freeze completely or partially, even with good cultivation. Spring sprouts are sparse or absent. Leaves may show damage as yellow or brown spots (Engeland, 1991; UMN Extension, 2024).

Why it works: Different garlic varieties have different frost hardiness. Softneck varieties (Allium sativum var. sativum) often overwinter poorly in regions with cold winters compared to hardneck varieties (Allium sativum var. ophioscorodon), which are better adapted to harsh conditions (Engeland, 1991; UMN Extension, 2024).

What to do: Choose winter garlic varieties adapted to your region. For areas with cold winters, hardneck varieties (Rocambole, Purple Stripe, Porcelain) are preferred (Engeland, 1991; UMN Extension, 2024). Softneck varieties (Artichoke, Silverskin) are better suited for mild winter regions (UMN Extension, 2024). Consult local nurseries and experienced gardeners to choose the right variety.

Lack of or Insufficient Mulching

Symptoms: After a harsh, snowless winter, plants freeze or are severely damaged. In spring, leaves may have brown or yellow spots, tips dried. Sprouts appear late and are weak (Engeland, 1991; UMN Extension, 2024).

Why it works: Mulch acts as insulation, protecting the soil and root system from sharp temperature fluctuations. It prevents deep soil freezing, protects cloves from frost heaving (being pushed to the surface), and retains moisture. Without mulch, in snowless, frosty winters, the soil freezes deeper, leading to clove damage or death (Engeland, 1991).

What to do: Mulch winter garlic plantings before the onset of sustained frosts (usually in November). Use a 4-6 cm layer of mulch from straw (weed-free), dry leaves, mown grass, or compost (Engeland, 1991; UMN Extension, 2024). In spring, when the danger of severe frost has passed, partially pull back mulch from plants so the soil warms faster, then return it to retain moisture and control weeds (UMN Extension, 2024). In regions with consistent snow cover, mulch is not obligatory but is recommended as a precaution (Engeland, 1991).

Autumn Soil Waterlogging

Symptoms: Plants root poorly, look pale in autumn. In winter, cloves rot, spring sprouts are absent. Upon digging, rotting cloves with a foul odor are found (Brewster, 2008).

Why it works: Autumn soil waterlogging, especially on heavy soils, causes cloves not to root but to rot. In wet, cold soil, fungal diseases (Pythium, Fusarium) become active. Furthermore, wet cloves are more vulnerable to frost heaving and ice damage (Brewster, 2008).

What to do: Choose well-drained sites for planting. Do not plant winter garlic in low-lying areas where water accumulates. If autumn is rainy, consider planting on raised beds or ridges to drain excess moisture. When planting in heavy soil, add sand and organic matter to improve drainage (Engeland, 1991).

Pest and Disease Damage

Symptoms: Plants emerge from winter weakened, with damaged leaves, or fail to appear. Upon digging, cloves show signs of rot (White Rot, Fusarium), damage by nematode, or pest larvae (Brewster, 2008; Entwistle, 1990).

Why it works: Cloves weakened by diseases or damaged by pests cannot withstand winter stresses. Fungal pathogens actively develop in conditions of dampness and low temperatures. Nematode and pest larvae damage tissues, opening the way for infections (Brewster, 2008).

What to do: Prevention: use healthy planting material, heat-treat cloves before planting (45°C, 2-3 hours), practice crop rotation, remove and burn diseased plants (Brewster, 2008). In autumn, you can drench the soil with biological products (Trichoderma, Bacillus subtilis) to suppress pathogenic fungi (Brewster, 2008).

Insufficient Rooting

Symptoms: In spring, plants emerge weak, with few roots. Upon digging, the root system is poorly developed, the clove has hardly used its reserves (Engeland, 1991).

Why it works: For successful overwintering, garlic needs a robust root system to supply water and nutrients in spring. Lack of autumn moisture, compacted soil, or phosphorus deficiency can hinder root development. Without a developed root system, the plant cannot start growing quickly in spring and often dies (Engeland, 1991).

What to do: Apply phosphorus fertilizers (superphosphate) at planting to stimulate root development. Provide watering if autumn is dry. Cultivate the soil to ensure oxygen access to roots. After planting, if autumn is dry, water 1-2 times for good rooting (Engeland, 1991).

How to Distinguish Causes of Poor Overwintering?

Important Note: Garlic winter hardiness is a complex property dependent on variety, weather, and cultivation practices. In severe winters, even well-prepared plants may be damaged. It's important to assess the overall percentage of overwintered plants and the condition of those that survived. If 15 out of 20 plants survived and look healthy – that's a normal result. If less than 50% survived – you should reconsider your cultivation practices and variety choice (Engeland, 1991).

Variety Characteristics and Non-bolting Varieties

Symptoms: Scapes are completely absent, even on plants expected to bolt. Or scapes appear but are short, thin, and fail to develop into full flower stalks (Engeland, 1991).

Why it works: Not all garlic varieties produce scapes. Softneck varieties (Allium sativum var. sativum) – Artichoke, Silverskin – usually do not bolt. Hardneck varieties (Allium sativum var. ophioscorodon) – Rocambole, Purple Stripe, Porcelain – do bolt, but in some climates or with certain agronomic errors, scapes may be weak or underdeveloped (Engeland, 1991; UMN Extension, 2024).

What to do: Before raising an alarm, make sure you planted a bolting variety. If you are growing softneck garlic, the absence of scapes is normal. If you planted a hardneck variety and the scapes are weak or absent, look for other causes (Engeland, 1991).

Nutrient Deficiency (Especially Potassium and Phosphorus)

Symptoms: Scapes are thin, short, pale, may bend. Inflorescences are small, bulbils underdeveloped. Leaves often yellow at the edges or have a purple tinge (phosphorus deficiency). Plants appear weakened (Brewster, 2008).

Why it works: To form a robust scape, the plant needs significant nutrient reserves, especially potassium and phosphorus. Potassium is responsible for carbohydrate transport and overall tissue tone, phosphorus for energy metabolism and generative organ development. When deficient, the scape forms weakly, and bulbils are small or fail to set (Brewster, 2008).

What to do: Apply a complete fertilizer with emphasis on potassium and phosphorus (e.g., monopotassium phosphate). Add ash (potassium source) and superphosphate. Fertilize during the scape emergence period (late May – early June). For organic gardening, use wood ash (1 cup per 1 m²) or bone meal (phosphorus source) (Brewster, 2008; Engeland, 1991).

Viral Infections (Onion Yellow Dwarf Virus (OYDV) and others)

Symptoms: Scapes are deformed, bent, may have yellow stripes or streaks. Inflorescences are underdeveloped, bulbils small or absent. Plants in general appear depressed, leaves may have mosaic coloring, curl. Sometimes dwarfism is observed (Brewster, 2008; Walkey, 1990).

Why it works: Some viruses affecting garlic disrupt cell division and differentiation processes at growing points, including flower bud primordia. This leads to scape deformation, bulbil underdevelopment, and general plant weakening. Viruses are transmitted through infected planting material and insect vectors (aphids, thrips) (Brewster, 2008).

What to do: Treatment is impossible. The main method is prevention: use healthy, certified planting material. Remove and burn plants with suspicious symptoms. Control insect vectors (Brewster, 2008).

Stem Nematode (Ditylenchus dipsaci)

Symptoms: Scapes are bent, thickened, may have blisters. Inflorescences are deformed, bulbils underdeveloped or absent. Leaves are curled, plants are stunted (Brewster, 2008; Engeland, 1991).

Why it works: The nematode penetrates scape tissues and feeds on cell sap, causing tissue hypertrophy and deformation. This leads to scape bending and inflorescence underdevelopment (Brewster, 2008).

What to do: Treatment is impossible. Prevention: heat-treat cloves before planting (45°C, 2-3 hours), use healthy planting material, practice crop rotation, remove and burn affected plants (Brewster, 2008).

Frost Damage (Spring Frosts)

Symptoms: Scapes are bent, twisted, with brown or yellow patches – traces of freezing. Scape tips may dry out. Inflorescences are often underdeveloped (Engeland, 1991).

Why it works: The garlic scape is a delicate, actively growing tissue. Spring frosts, especially during scape emergence (May – early June), can damage cells, disrupt growth, and cause deformation. Even light freezing (down to -2…-3°C) can bend the scape (Engeland, 1991).

What to do: Protect plantings from returning frosts. Use protective covers (agrofabric, spunbond) overnight when frost is threatened. Mulching helps retain soil heat. Frost-damaged scapes will not recover, but this is not critical: remove them to improve bulb growth (Engeland, 1991).

Lack of Moisture (Drought) during Scape Formation

Symptoms: Scapes are thin, short, pale, may bend. Inflorescences are small, bulbils underdeveloped. Plants appear depressed, leaves lose turgor (Engeland, 1991).

Why it works: During scape formation (May – June), garlic needs sufficient moisture. Lack of water slows all growth processes, including flower stalk development. The scape forms weakly, and bulbils are small or fail to set (Brewster, 2008).

What to do: Ensure regular watering during scape formation (late May – early June). The soil should be moist but not wet. Water 1-2 times per week, using 2-3 buckets of water per 1 m². In hot weather, increase frequency (Engeland, 1991).

Natural Variability (Weather Vagaries)

Symptoms: In some years, scapes are weaker or stronger, even with the same cultivation practices. Yields may vary by year (Engeland, 1991).

Why it works: Scape formation depends on a complex of conditions: temperature, humidity, light. In cold or, conversely, very hot and dry years, scapes may be weaker. This is a natural reaction of plants to stress conditions (Engeland, 1991).

What to do: If scapes are weak only in one year but normal in others, it's likely a weather factor. Assess the situation over several years. If the problem repeats year after year, look for other causes (Engeland, 1991).

How to Distinguish Causes of Weak or Deformed Scapes?

Important Note: The garlic scape is not only an indicator of plant health but also valuable planting material (bulbils) for variety rejuvenation. Even if scapes are weak, don't rush to remove them: they may still produce bulbils for renewing planting material. However, remember that to obtain large bulbs, it is recommended to remove (snap off) scapes when they have fully unfolded above the leaves and started to curl, directing the plant's energy to bulb formation (Engeland, 1991).

Lack of Moisture (Drought) and Soil Overheating

Symptoms: Plants turn yellow prematurely, starting with lower leaves, then the process quickly spreads upwards. Leaves lose turgor, become limp, then completely dry out. Bulbs are small, cloves loose, underdeveloped. When dug up, the soil is dry and hard (Engeland, 1991; Brewster, 2008).

Why it works: Garlic, especially during bulb formation (June – July), needs sufficient moisture. When deficient, the plant switches to stress mode, accelerates aging processes, and prematurely completes its life cycle to preserve viability for at least some reproductive organs (cloves). In hot, dry weather, this process accelerates. Additionally, soil overheating (>30°C) also triggers premature maturation (Brewster, 2008).

What to do: Ensure regular watering during active growth and bulb formation (late May – July). The soil should be moist but not wet. In dry weather, water 1-2 times per week (Engeland, 1991). Use mulch to retain soil moisture and protect roots from overheating (UMN Extension, 2024). Stop watering 2-3 weeks before harvest for better bulb maturation (Engeland, 1991).

Nitrogen Deficiency (Early Nitrogen Starvation)

Symptoms: Leaves turn yellow prematurely, starting from the lower, older ones. Yellowing spreads evenly across the leaf blade. Plant growth is slow, they appear weakened. Bulbs are small, underdeveloped (Brewster, 2008).

Why it works: Nitrogen is a key element for plant growth and development. Its deficiency during active vegetation (spring – early summer) means the plant cannot maintain normal leaf growth. Premature aging and leaf death trigger premature bulb maturation (Brewster, 2008).

What to do: Apply an early spring nitrogen fertilizer (urea, ammonium nitrate, or organic sources – manure infusion, poultry manure, blood meal). Nitrogen is applied in the first half of the growing season, before active bulb formation begins (Engeland, 1991). Be careful not to overdo it, as excess nitrogen delays maturation and reduces storage life (Brewster, 2008).

Root Problems (Root Damage)

Symptoms: Plants turn yellow prematurely, wilt, as if lacking moisture, but the soil may be wet. When pulled out, the root system is weak, damaged, or rotting. This can result from waterlogging, soil compaction, deep cultivation, pest damage (onion fly larvae, wireworm), or diseases (Fusarium, White Rot) (Brewster, 2008; Engeland, 1991).

Why it works: Damaged roots cannot supply the plant with water and nutrients. The plant experiences stress, triggering premature aging mechanisms. As a result, vegetation ends early, and the bulb fails to gain mass (Brewster, 2008).

What to do: Identify and eliminate the cause of root damage. If it's waterlogging – normalize watering and improve drainage. If it's soil compaction – cultivate between rows. If it's pests or diseases – apply appropriate control measures (Brewster, 2008). To stimulate root growth, use preparations based on humic acids or phosphorus-potassium fertilizers (Brewster, 2008).

Disease Infestation (Fusarium, White Rot, Pink Rot)

Symptoms: Plants turn yellow and wilt prematurely, the process often occurring in patches. Characteristic signs of diseases appear on bulbs and roots: pink, white, or yellowish-brown coating (Fusarium), white fluffy coating with black dots (White Rot), pink roots (Pink Rot) (Brewster, 2008; Entwistle, 1990).

Why it works: Fungal pathogens disrupt water and nutrient transport, secrete toxins, leading to premature leaf death and accelerated bulb maturation. Affected plants often fail to reach full mass (Brewster, 2008).

What to do: Prevention: use healthy planting material, practice crop rotation, remove and burn diseased plants, apply biological products (Trichoderma, Bacillus subtilis). Treatment of affected plants is impossible – they are removed (Brewster, 2008).

Pest Damage (Onion Fly, Stem Nematode)

Symptoms: Leaves turn yellow prematurely, wilt, plants are stunted. Upon inspection, onion fly larvae are found at the stem base or in the bulb, or characteristic nematode deformities and blisters on tissues (Brewster, 2008; Engeland, 1991).

Why it works: Onion fly larvae damage bulb tissues and the stem base, disrupting nutrition and causing premature wilting. Nematode sucks sap and destroys tissues, leading to stress and accelerated maturation (Brewster, 2008).

What to do: For onion fly control, use insecticides or repellent methods (planting carrots near garlic). Against nematode, only prevention helps: heat-treating cloves before planting (45°C, 2-3 hours), using healthy planting material, practicing crop rotation (Brewster, 2008).

Natural Variety Characteristics (Very Early Varieties)

Symptoms: The variety consistently matures earlier than others, regardless of weather or cultivation. Bulbs form normally, of the size typical for the variety (Engeland, 1991).

Why it works: Some garlic varieties are biologically programmed for early maturation. This is not a problem but a varietal trait. For example, some hardneck varieties mature as early as late June – early July (Engeland, 1991).

What to do: If you planted an early-maturing variety, premature maturation is normal. It's important to choose the correct planting and harvest times for the specific variety. When purchasing planting material, check the maturity dates and use them as a guide (Engeland, 1991).

How to Distinguish Causes of Premature Maturation?

Important Note: Premature maturation is most often a signal of stress. It's important to learn to distinguish stress-induced maturation from natural maturation. Normally, garlic begins to mature in the second half of July (for winter varieties) or in August (for spring varieties), when bulb formation is complete. If the plant starts yellowing in early June, when the bulb is just beginning to form – this is a clear sign of a problem. In this case, you need to identify the cause as quickly as possible and, if possible, eliminate it. However, remember: leaves damaged by stress do not recover, but eliminating the cause will help preserve the remaining healthy plants and get at least part of the harvest (Engeland, 1991).

Comparative Table: Diseases, Pests, and Physiological Disorders

Step-by-Step Rapid Diagnosis Algorithm

Use the following algorithm for rapid diagnosis:

1. Examine the affected part of the plant.

• If you see the pest (larva, caterpillar, beetle, mite) or its clear traces (excrement, tunnels, egg masses) – it's a pest.
• If you see a pathogen (coating, spots with spores, rot with odor, sclerotia) – it's a disease.
• If there is no pest or pathogen, and symptoms look like changes in color, shape, or size without visible damage – it's a physiological disorder.

2. Assess the distribution pattern.

• Patches, circles, spots in the field – often indicate a disease or nematode.
• Single affected plants – may indicate a pest or local damage.
• Uniform yellowing or depression across the field – most often a physiological disorder (nutrient deficiency, drought, waterlogging).

3. Analyze agronomic practices and weather.

• Ask yourself: "What did I do wrong?". If you didn't water garlic for a week in hot weather – it's drought. If you watered heavily during a rainy week – it's waterlogging. If you didn't fertilize on poor soil – it's nutrient deficiency.
• If agronomy is correct but there is a problem – consider a disease or pest.

4. Remember when symptoms appeared.

• Link the timing of symptom appearance with garlic growth stages. For example:
• Early spring (April-May) – more often nutrition or moisture issues.
• Late May-June – active growth and bulb formation, peak activity of diseases and pests.
• July – natural maturation. If yellowing occurs earlier – it's stress.

5. Perform the "pull test".

• Carefully pull out 1-2 problematic plants. If they pull out easily, and roots are absent or rotting – it's a disease (White Rot, Fusarium) or root damage. If roots are fine – the problem is above-ground (nutrient deficiency, drought, pests on leaves).

Typical Diagnosis Mistakes and How to Avoid Them

When Laboratory Diagnosis is Needed

It is not always possible to make an accurate diagnosis "by eye," especially with mixed infections (e.g., virus + nematode) or atypical manifestations. In such cases, it is recommended to contact a diagnostic laboratory. This is especially important when suspecting:

• Stem Nematode (Ditylenchus dipsaci) – a quarantine pest requiring strict measures.
• White Rot (Sclerotium cepivorum) – a dangerous disease with long-term soil persistence.
• Viral infections – for confirmation and to rule out mixed infections.
• Atypical symptoms that cannot be linked to known causes.

Send several samples to the laboratory: the whole affected plant (with roots), a soil sample from the root zone, and, if possible, photos of the symptoms. This will help speed up and improve diagnosis (Brewster, 2008).

Summary: Three Main Questions for Rapid Diagnosis

Ask yourself three questions when you spot a problem:

1. Do I see the pest or its traces? → Yes → Pest. → No → Proceed to question 2.

2. Do I see a pathogen (coating, rot with characteristic signs)? → Yes → Disease. → No → Proceed to question 3.

3. Can I link the symptom to a specific care error (watering, fertilizing, weather)? → Yes → Physiological disorder. → No → Likely requires laboratory diagnosis.

Remember: successful problem management starts with correct diagnosis. Careful observation of plants, knowledge of their biological features, and a systematic approach will help you quickly and accurately identify problems and make the right decisions. We wish you healthy, robust plants and bountiful harvests!