Diseases

1.1. Leaf Rosette: The Perfect "Incubator"

Broccoli forms a dense, ground-hugging rosette of large, succulent leaves. This architecture itself creates a microclimate with high humidity at the soil surface and between the leaves. Air stagnates here, and moisture after watering or rain evaporates slowly (Teverson, 2020). This creates ideal conditions for the germination of spores of many pathogens — from fungi causing Alternaria and downy mildew to bacteria that provoke rots.

Takeaway for the gardener: Understanding this fact suggests the first rule of prevention — ensuring good ventilation. Dense plantings aggravate this natural tendency, so following planting spacing is not a whim but a critically important measure.

1.2. Tender Tissues — Easy Prey

Broccoli leaves, unlike those of white cabbage, have a thinner cuticle (waxy layer). This makes them vulnerable to pathogen penetration. Fungal spores and bacteria easily germinate and penetrate tissues. According to research, seedlings and young plants are most susceptible, as their defense mechanisms are not yet fully developed (Akhatov et al., 2013). Furthermore, broccoli has a poorly developed root system compared to its leaf mass, which can cause water stress and weaken the plant.

Takeaway for the gardener: Broccoli needs particularly careful care in the early stages. Any stress (lack of moisture, overheating, pest damage) lowers its natural immunity and opens the "gate" to infection.

1.3. Dependence on Humidity and Temperature

Most broccoli pathogens become active under specific conditions. Fungal diseases (late blight, Alternaria, downy mildew) thrive in cool, humid conditions. Bacterial diseases (vascular bacteriosis, soft rot) develop at higher temperatures and during prolonged rains or frequent overhead watering (Teverson, 2020; Startsev, 2021).

Temperature stress also plays a role. For example, Fusarium wilt is more common in hot weather when the weakened plant cannot effectively resist the fungus clogging its vessels. The optimal temperature for broccoli head formation is between +12 and +20°C (Basics of Broccoli Production, 2024). Any deviation is a danger signal, as disease resistance drops sharply outside the crop's comfort zone.

Takeaway for the gardener: Monitoring the weather is your additional insurance. Knowing the forecast allows you to carry out preventive treatments in advance. The ability to link weather anomalies to subsequent disease outbreaks is the key skill of an experienced gardener.

1.4. The Role of Planting Density and Crop Rotation

Planting density directly affects three key factors: humidity, nutrition, and disease spread.

• Humidity: In dense plantings, moisture evaporates more slowly.
• Nutrition: Plants compete for light and nutrients, leading to weakening.
• Spread: Pathogens are easily transmitted from a diseased plant to a healthy one through contact, water droplets, or insects.

An equally important factor is the preceding crops. Pathogens of many diseases (especially clubroot and Fusarium) accumulate in the soil for years. Continuously growing brassicas in the same place turns the soil into a "breeding ground" for infection, which is almost impossible to control with chemical methods. This principle is the foundation of integrated pest management and is confirmed by numerous studies (Akhatov et al., 2013; Startsev, 2021).

Takeaway for the gardener: Remember that prevention starts with planning. Plan your planting scheme, rotate crops, and this will become your most powerful weapon against diseases.

2.1. Damping-off (Complex Disease)

This is not one specific pathogen but a group of soil-borne fungi and fungus-like organisms that cause similar symptoms. The most common culprits are fungi of the genus Fusarium, Rhizoctonia, and oomycetes of the genus Pythium (Startsev, 2021). This is why the approach to treatment and prevention must be comprehensive.

Symptoms: The main sign is darkening, thinning, and rotting of the root collar (the transition point between stem and root) (Akhatov et al., 2013). The stem base becomes watery, turns brown, and softens. The plant collapses as if cut at the very base and quickly dies.

How to distinguish from other problems: If seedlings are simply stretched and fall over due to lack of light — that's lodging, but the stem remains healthy, firm, and green. With damping-off, it clearly darkens and rots. Also, if the roots have simply dried out, the plants wilt gradually rather than "falling" en masse near the ground.

Causes and development conditions: The disease literally "loves" our mistakes. Its development is promoted by overwatering of the substrate, acidic soil reaction, dense sowing, poor ventilation, and sharp temperature fluctuations (Startsev, 2021). Spores of these fungi can persist for a long time in contaminated soil and on plant debris.

What to do:

1. Disinfection: For sowing, use only fresh, high-quality purchased soil from trusted producers or sterilize your own. The most reliable method for small volumes is steaming.

2. Seed treatment: Before sowing, seeds can be soaked in a solution of biological products based on hay bacillus (Bacillus subtilis), for example, Fitosporin-M (Akhatov et al., 2013). This creates a protective barrier around the sprout.

3. Agronomy: Don't overcrowd your sowings! Prick out seedlings on time, ensure good drainage, and don't overwater. Loosening the top layer of soil after watering helps it dry out faster.

2.2. Rhizoctonia

This disease is caused by the fungus Rhizoctonia solani and can affect plants at different stages, but it is especially dangerous for seedlings.

Symptoms: Unlike damping-off, the stem base becomes not wet and rotting but dark and dry, as if "constricted." Plants appear stunted and lag in growth. Dark, sunken spots may form on the roots (Teverson, 2020; Akhatov et al., 2013).

How to distinguish: With Rhizoctonia, seedlings don't fall en masse but seem to "freeze" in growth. Some plants may die, and those that survive remain sick for a long time after transplanting (Akhatov et al., 2013). This distinguishes it from the rapid damping-off.

Causes: The fungus prefers higher temperatures (+25°C and above), which is relevant for hot greenhouses. It also persists in soil and on plant debris.

What to do:

1. Sterilization: The same measures as for damping-off — clean soil and clean containers.

2. Climate control: Avoid overheating seedlings. Timely ventilation is the key to health.

3. Bioproducts: The same bacteria Bacillus subtilis (e.g., the product "Seradis ASO") are effective against Rhizoctonia (Teverson, 2020). They are applied to the soil via watering.

2.3. Root Rot (Pythium)

Pathogens of the genus Pythium are other common inhabitants of waterlogged soils.

Symptoms: Seeds may rot before emergence (poor germination). If the plant does emerge, the roots become watery, turn brown, and die. The plant wilts and dies, often after the appearance of 1-2 true leaves (Akhatov et al., 2013).

How to distinguish: Pythium infection often occurs in patches. If all seedlings are lethargic — the problem is likely watering or nutrition. If individual "bald patches" die in the box, and the root collar on neighboring plants doesn't blacken — it's likely Pythium.

What to do: The main measure is water management. Water only when the top layer of the substrate has dried out. Use drainage holes. For prevention, you can drench the soil with a Fitosporin-M solution.

General for All Seedling Diseases: Prevention

All three groups of pathogens share one thing: they are very resistant in the external environment and persist in the soil for a long time. Therefore, the main principles of seedling protection are unified:

1. Healthy Start: Use quality seeds. Modern hybrids often have a marking indicating pre-sowing treatment.

2. Sterility: Wash and disinfect trays and boxes. Do not use old, untested soil.

3. Humidity: The golden rule is moderate watering. Better to underwater than to overwater.

4. Ventilation: Ventilate the greenhouse to reduce air humidity and avoid sharp temperature fluctuations.

5. Bioprotection: Using biological products based on hay bacillus or Trichoderma is an eco-friendly way to create a protective barrier.

The main thing to remember: At the seedling stage, it is much easier to prevent a disease than to treat it. If you lose time, saving weakened plants will be practically impossible.

3.1. Clubroot (Plasmodiophora brassicae)

This is one of the most dangerous and insidious diseases for all brassicas, including broccoli.

Symptoms: The main and most characteristic sign is the formation of swellings (galls) on the roots. These galls can vary in size — from a pea to a fist (Teverson, 2020; Startsev, 2021). Initially white, they darken and rot over time. The above-ground part of the plant looks stunted: leaves turn yellow, especially in hot weather, the plant is stunted and may die (Akhatov et al., 2013).

How to distinguish from other problems:

• From nutrient deficiency: With nutrient deficiency, yellowing is usually uniform or on older leaves, and the roots remain healthy.
• From pest damage: Galls caused by the cabbage weevil larva have a tunnel inside made by the larva (Startsev, 2021). With clubroot, the swelling is filled with fungus spores.
• From stress: During drought or waterlogging, the plant wilts, but its roots do not have swellings.

Causes and development conditions: The pathogen is a fungus-like organism that lives in the soil as spores and can remain viable for up to 15-20 years. Spores germinate only in the presence of root exudates from plants of the Brassicaceae family. Optimal conditions for development: acidic soil (pH 5.5-6.5), high humidity (75-90%), and warm weather (soil temperature +18...+24°C) (Teverson, 2020; Akhatov et al., 2013). At soil temperatures below +15°C, infection practically does not occur. Spores are transmitted through infected seedlings, with soil on tools, and with meltwater and rainwater.

What to do: Clubroot is easier to prevent than to cure.

1. Crop rotation: This is the main rule. Do not return brassicas to an infected area for at least 3-4 years, and preferably 5-7 years.

2. Liming: Maintain soil pH at 7.0-7.2. Adding lime does not kill the spores but creates unfavorable conditions for them (Teverson, 2020). Even increasing pH from 5.5 to 6.5 significantly reduces disease development (Akhatov et al., 2013).

3. Variety selection: There are broccoli hybrids resistant to certain races of clubroot. For example, the "Kilaton," "Kilafur" series from Syngenta (Akhatov et al., 2013). However, remember that resistance is not absolute — on heavily infected soil, even resistant varieties can be affected, especially by new races of the pathogen.

4. Cleanliness: Use only tested soil, free from clubroot spores, for seedlings.

5. Weed control: Destroy weeds from the Brassicaceae family (shepherd's purse, wild mustard, wild radish), which are reservoirs of infection (Teverson, 2020).

3.2. Fusarium Wilt (Fusarium oxysporum f. sp. conglutinans)

This disease is a real scourge for broccoli in warm regions. The pathogen is a fungus that clogs the plant's vessels.

Symptoms: The first and most important sign is one-sided yellowing of the leaves. Not the whole leaf turns yellow, but only one half or part along the veins (Startsev, 2021). Then the leaf wilts, loses turgor, curls, and falls off. On a cross-section of the stem or petiole, a darkened ring of vessels is visible — this is the main diagnostic sign (Akhatov et al., 2013). With severe infection, the plant dies, the head does not form or is deformed.

How to distinguish:

• From vascular bacteriosis: In bacteriosis, the blackening of vessels is blacker, and V-shaped yellow zones bounded by veins form on the leaves. In Fusarium, yellowing is often one-sided, without clear V-shaped zones.
• From nitrogen deficiency: With nitrogen deficiency, the old, lower leaves turn yellow evenly. In Fusarium, the process starts on one side or from individual veins and quickly spreads to the whole plant.
• From clubroot: In clubroot, the roots are deformed. In Fusarium, the roots appear externally healthy.

Causes and development conditions: The fungus enters the plant through roots or mechanical damage and spreads upward through the vessels. It can persist in the soil for many years, and its development is favored by hot (+25...28°C) and dry weather. At soil temperatures below +15°C, fungal development slows down (Startsev, 2021).

What to do:

1. Resistant varieties: This is the most effective method. Many modern broccoli hybrids have resistance to Fusarium.

2. Crop rotation: The fungus persists in the soil, so it is recommended not to return brassicas to the same place for at least 3-4 years.

3. Removal of diseased plants: If single foci of infection are found, the affected plants should be dug up by the roots and destroyed (burned), and the spot treated with a solution of copper sulfate (Akhatov et al., 2013).

4. Early planting: In regions with hot climates, it is recommended to plant seedlings as early as possible so that the plants have time to develop before the peak temperatures when the fungus is most active (Startsev, 2021).

3.3. Rhizoctonia on Roots of Adult Plants

We already discussed this pathogen in the seedling section, but it can also affect adult plants.

Symptoms: Sunken, brown or black spots appear on the roots and at the base of the stem. The root collar becomes dry and cracks. Externally, this manifests as stunting and wilting, especially in hot weather (Teverson, 2020).

How to distinguish:

• From clubroot: Rhizoctonia does not cause characteristic swellings on the roots. It can be distinguished by appearance — dark, dry, "constricted" roots.
• From Fusarium: In Rhizoctonia, there is no characteristic one-sided yellowing or darkened vascular ring on the stem cross-section.

Causes: The fungus lives in the soil and becomes active at temperatures above +20°C and high humidity.

What to do:

1. Crop rotation: As with other soil-borne pathogens, a break in growing brassicas is necessary.

2. Bioproducts: Applying preparations based on Bacillus subtilis or Trichoderma to the soil during planting can help protect the root system.

3. Agronomy: Avoid dense plantings, which create a favorable microclimate for disease development. Loosening between rows helps the soil dry out.

Summary Table for Quick Diagnosis

Important to remember: The main weapons against root diseases are crop rotation and maintaining soil health. Grow broccoli in the same place no more than once every 3-4 years, maintain a neutral soil reaction, use healthy seedlings and resistant varieties. This will significantly reduce the risk of crop loss.

4.1. Alternaria (Dark Leaf Spot)

This is one of the most common fungal diseases of broccoli, caused by fungi of the genus Alternaria (A. brassicae and A. brassicicola).

Symptoms: Characteristic dark brown or almost black spots appear on the leaves. The spots have a concentric (ring-like) structure — like a "target" (Teverson, 2020). Over time, the spots enlarge, may coalesce, and the affected tissue in the center dies and becomes dry, sometimes with a noticeable spore coating (Akhatov et al., 2013). With severe infection, leaves turn yellow and fall off.

How to distinguish from other problems:

• From bacterial spot: Bacterial spots are often angular, bounded by veins, and surrounded by a watery or oily border. Alternaria spots are rounded, with clear concentric circles.
• From downy mildew: In downy mildew, a whitish or grayish coating appears on the underside of the leaf, and the spots on the upper side are yellowish, vague, often bounded by veins (Teverson, 2020).

Causes and development conditions: The fungus is particularly active in warm (+20...+25°C) and humid weather. Spores are spread by rain, wind, and on plant debris. Infection occurs in the presence of free moisture on the leaves (Teverson, 2020). The source of infection can be both plant debris and infected seeds (Akhatov et al., 2013).

What to do:

1. Crop rotation: The fungus persists in plant debris, so it should be thoroughly incorporated into the soil or removed from the field.

2. Preventive treatments: During rainy periods, it is recommended to carry out treatments with fungicides (copper-based or biological). It's important to start treatments when the first symptoms appear, as the disease develops quickly (Teverson, 2020).

3. Resistant varieties: Some broccoli hybrids have increased resistance to Alternaria.

4.2. Downy Mildew (Peronospora)

The pathogen is a fungus-like organism Hyaloperonospora brassicae. This is one of the most common problems, especially during the seedling stage and in conditions of high humidity.

Symptoms: Vague yellowish or pale green spots appear on the upper side of the leaf, often bounded by veins (Teverson, 2020). On the underside of the leaf, directly under these spots, a whitish, grayish, or purplish coating forms — this is the sporulation of the fungus (Akhatov et al., 2013). With severe infection, leaves turn yellow, deform, and dry out.

How to distinguish:

• From Alternaria: In Alternaria, the spots are dark, concentric, without coating on the underside.
• From nutrient deficiency: With nutrient deficiency (nitrogen, potassium), leaf yellowing is more uniform, without distinct spots and coating.

Causes and development conditions: The pathogen prefers cool weather (+10...+16°C) and high humidity. Spores germinate in the presence of free moisture on the leaves (Teverson, 2020). The fungus can also persist in the soil as spores (oospores) for several years. Infection is often introduced with infected seedlings (Teverson, 2020).

What to do:

1. Prevention on seedlings: It is important not to overwater seedlings and to ensure good ventilation. Spores can spread even after 30 minutes of leaf wetness (Teverson, 2020).

2. Removal of diseased leaves: When the first symptoms appear, remove the affected leaves.

3. Fungicides: Preparations containing mancozeb or copper are effective against downy mildew. Treatments should be carried out at the first signs of the disease or during periods favorable for its development (rainy, cool weather).

4. Crop rotation: As with Alternaria, a break of 2-3 years in growing brassicas is necessary.

4.3. Bacterial Spots

There are several types of bacteria that cause spots on broccoli leaves. The most common are black bacterial spot (Xanthomonas campestris pv. armoraciae / raphani) and bacterial spot (Pseudomonas syringae pv. maculicola). Both diseases often appear together, making diagnosis difficult (Akhatov et al., 2013).

Symptoms: Numerous small, angular, watery spots appear on the leaves, which darken over time (becoming dark brown or almost black). The spots are often bounded by small veins, giving them an angular shape. A yellow or watery border may be visible around the spots (Akhatov et al., 2013). With severe infection, leaves turn yellow, dry out, and fall off.

How to distinguish:

• From Alternaria: Bacterial spots are small, angular, without concentric rings.
• From downy mildew: No coating on the underside of the leaf.

Causes and development conditions: Bacteria are spread by raindrops, irrigation water, insects, and through mechanical damage. Infection is favored by warm (+25...+30°C) and humid weather with free moisture on the leaves (Akhatov et al., 2013). Bacteria persist on plant debris and seeds.

What to do:

1. Use of healthy seeds: Bacteria can be transmitted with seeds. Use seeds from trusted suppliers or treat them with hot water (+50°C for 20 minutes) (Basics of Broccoli Production, 2024).

2. Crop rotation: Remove and destroy plant debris after harvest.

3. Pest control: Bacteria enter through wounds made by insects, so controlling flea beetles, aphids, and other pests is important (Akhatov et al., 2013).

4. Copper-containing preparations: Preventive treatments with copper-containing preparations (e.g., Bordeaux mixture) help curb bacterial development. But remember that copper is a heavy metal, so use it with caution and only when necessary.

4.4. Summary Table for Diagnosis of Leaf Diseases

Important to remember: All leaf diseases develop faster in conditions of high humidity and lack of ventilation. Therefore, agronomic practices — proper planting patterns, timely loosening, removal of lower old leaves — work to prevent most of them. Often, optimizing growing conditions and removing affected plant parts is enough to stop the disease.

5.1. Vascular Bacteriosis (Black Rot) (Xanthomonas campestris pv. campestris)

This disease is considered one of the most serious for brassicas worldwide. In the past, it regularly led to significant crop losses, but with improved seed quality control, the situation has changed for the better (Teverson, 2020). Nevertheless, the risk remains, and it is important to be able to recognize the disease at an early stage.

Symptoms: The most characteristic sign is V-shaped yellow zones that start from the leaf edge and narrow towards the center (Teverson, 2020). In these zones, the veins become dark, almost black — this is the main diagnostic sign (Akhatov et al., 2013). As the disease progresses, the affected tissue areas die, becoming dry and brittle. In advanced cases, the infection spreads through the vessels into the stem, and a blackened ring of vessels can be seen on its cross-section (Teverson, 2020). The plant may begin to wilt, and if the head is affected, it becomes unmarketable.

How to distinguish:

• From Fusarium: In Fusarium, yellowing is often one-sided (only on one side of the leaf) and does not form clear V-shaped zones. In vascular bacteriosis, the yellowing strictly follows the shape of a wedge narrowing towards the center of the leaf.
• From Alternaria: Alternaria causes rounded, concentric dark spots, not V-shaped yellowing.
• From potassium deficiency: Potassium deficiency leads to yellowing and necrosis of leaf margins, but without blackening of veins and without a clear V-shape.

Causes and development conditions: The main source of infection is infected seeds (Teverson, 2020). The bacterium can persist in plant debris, but it is the seeds that ensure its spread over long distances. In the field, the disease is spread by rain, irrigation, insects, and also by dirty equipment. The optimal temperature for development is about +25°C, and it takes 10-14 days for symptoms to appear (Teverson, 2020). Plants receiving overhead irrigation are most vulnerable, as the bacterium easily enters through hydathodes (pores on the leaf edges) (Teverson, 2020).

What to do:

1. Seed quality: Use only tested seeds, certified free from the pathogen. This is the most effective means of prevention (Teverson, 2020). When purchasing, check with the seller for seed testing results.

2. Hot water seed treatment: If there is suspicion that seeds may be infected, they can be treated in hot water (50°C for 20 minutes). But note that this may reduce germination (Basics of Broccoli Production, 2024).

3. Hygiene: All equipment, tools, and footwear must be clean, especially when moving from an infected area to a healthy one. Seedling trays and boxes must be disinfected after each use (Teverson, 2020).

4. Crop rotation: Do not grow brassicas on the infected area for 2-3 years to allow plant debris to completely decompose (Teverson, 2020).

5. Resistant varieties: There are broccoli hybrids with resistance to certain races of vascular bacteriosis. Check with seed suppliers for information.

6. Removal of diseased plants: If you notice single plants with signs of the disease, remove them by the roots and destroy them to prevent the spread of infection.

5.2. Fusarium Wilt (Yellows) (Fusarium oxysporum f. sp. conglutinans)

A fungal disease that also affects the vascular system, but its pathogen is a soil-borne fungus.

Symptoms: As with vascular bacteriosis, leaves turn yellow and wilt. But the main difference is that the yellowness often appears one-sidedly (Startsev, 2021). One half of the leaf turns yellow, while the other remains green. Also, on a cross-section of the stem, a dark ring of vessels is visible, but it has a brownish rather than black hue (Akhatov et al., 2013). With severe infection, leaves fall off, the head does not form or grows crookedly. The plant wilts and dies.

How to distinguish:

• From vascular bacteriosis: In bacteriosis — V-shaped yellow zones and black veins. In Fusarium — one-sided yellowing and a lighter, brown vascular ring.
• From lack of moisture: With lack of moisture, the plant wilts evenly, without selective yellowing.

Causes and development conditions: The pathogen is a soil-borne fungus that persists in the soil for many years (Startsev, 2021). It enters the plant through the roots and clogs the vessels. Hot (+25...+28°C) and dry weather favors development. At soil temperatures below +15°C, fungal development slows down (Startsev, 2021).

What to do:

1. Resistant varieties: This is the main and most effective method. Many modern broccoli hybrids have resistance to Fusarium. Be sure to check this parameter when choosing seeds.

2. Crop rotation: Return brassicas to the same place no earlier than after 3-4 years (Startsev, 2021).

3. Early planting: In regions with hot climates, plant seedlings as early as possible so that the plants have time to form before peak temperatures arrive.

4. Removal of diseased plants: When disease foci are found, dig up and destroy (burn) all affected plants along with their roots (Startsev, 2021). The place where they grew can be treated with a solution of copper sulfate (Akhatov et al., 2013).

5. Soil treatment: To increase plant resistance, biological products containing antagonistic microorganisms (e.g., based on Bacillus subtilis) can be used. They are applied to the soil during planting or via watering.

Summary Table: Vascular Diseases

Main conclusion: Both diseases are very dangerous and difficult to treat. Therefore, the main strategy is to prevent their occurrence. Healthy seeds, resistant varieties, proper crop rotation, and hygiene are your most reliable protection against vascular diseases of broccoli.

6.1. Gray Mold (Botrytis cinerea)

One of the most common diseases at all stages of broccoli cultivation and storage. The pathogen is a widespread fungus that affects weakened, damaged, or dying tissues.

Symptoms: Watery, softened brown areas appear on the inflorescence, especially at the base of the buds. In conditions of high humidity, a fluffy gray coating develops on them — this is the sporulation of the fungus (Akhatov et al., 2013). Over time, the affected head completely rots, turning into a slimy gray mass. Small black sclerotia — structures for surviving adverse conditions — may form on the tissues (Teverson, 2020).

How to distinguish:

• From bacterial rots: In gray mold, there is no unpleasant putrefactive odor characteristic of bacterial infections. The coating has a gray fluffy appearance, not slimy.
• From white mold: In white mold, the coating is white, cottony, not gray and fluffy.
• From physiological disorders: When overripe or damaged, the head simply turns yellow or brown, but without the characteristic coating and slimy consistency.

Causes and development conditions: The fungus is a typical saprophyte, preferring weakened tissues with damaged covers. Therefore, it often develops on frost-damaged, pest-damaged, or mechanically injured heads. Optimal conditions are high humidity and moderate temperatures (+15...+25°C). The fungus can also affect leaves and then move to the inflorescence (Akhatov et al., 2013).

What to do:

1. Preventing damage: Handle plants carefully during care and harvesting. Damaged tissues are entry points for infection.

2. Protection from overheating and hypothermia: Avoid stressful conditions that weaken the plant and increase the risk of infection.

3. Regular inspection: Timely remove old, dying leaves, as they serve as the first source of infection.

4. Proper storage conditions: After harvesting, quickly cool broccoli heads to +1...+2°C and maintain high air humidity (about 95%) to avoid wilting, which makes tissues more vulnerable to the fungus (Basics of Broccoli Production, 2024).

5. Crop rotation and destruction of plant debris: The fungus persists in the soil and on plant debris, so they must be thoroughly incorporated or removed.

6.2. White Mold (Sclerotinia sclerotiorum)

This disease, caused by the fungus Sclerotinia sclerotiorum, can affect many crops, including broccoli. It is especially dangerous as it develops very quickly.

Symptoms: Watery, soft, softened areas appear on the inflorescence, stems, petioles, and leaves. The affected tissue is quickly covered with abundant white cottony coating (Akhatov et al., 2013). On the coating and inside the tissues, black dense sclerotia form — rounded or irregularly shaped, ranging from a few millimeters to 1-2 cm in size (Teverson, 2020). The infection spreads rapidly from plant to plant, especially through direct contact.

How to distinguish:

• From gray mold: In gray mold, the coating is gray, fluffy. In white mold, it is white, cottony, denser. Additionally, white mold often forms black sclerotia.
• From bacterial rot: Bacterial rot has an unpleasant odor and slimy exudates, not cottony ones.

Causes and development conditions: The fungus can affect both living and dying tissues. The greatest risk of infection occurs in the presence of injuries (wounds, frost damage) and a source of infection in the soil or on plant debris. Cool (+15...+20°C) and humid weather favors development (Akhatov et al., 2013). Spores are spread by air and can persist in the soil for a long time.

What to do:

1. Preventing damage: As with gray mold, protecting plants from mechanical damage and pests is a key preventive measure.

2. Crop rotation: A mandatory break in growing brassicas in the infected field for 3-4 years, as sclerotia remain viable in the soil for up to 5 years or more (Akhatov et al., 2013).

3. Destruction of plant debris: Thorough cleaning and incorporation of plant debris reduces the infection reservoir.

4. Deep plowing: Sclerotia buried deeper than 15 cm cannot germinate and form apothecia (fruiting bodies that release spores) (Startsev, 2021).

6.3. Bacterial Rots (Pectobacterium spp., Pseudomonas spp.)

Bacteria that cause soft rots are secondary pathogens that often attach to already damaged tissues. However, under favorable conditions, they can also affect healthy tissues, causing rapid spoilage of the crop.

Symptoms: The affected tissue becomes watery, softened, slimy, with a characteristic unpleasant putrefactive odor (Teverson, 2020). When the head is cut, it is visible that the rot spreads from the damaged area into the interior of the inflorescence. Bacterial rots often develop at sites of damage caused by insects, hail, during harvesting, and in rainy weather (Akhatov et al., 2013).

How to distinguish:

• From fungal rots: The main difference is a sharp putrefactive (sour or ammonia) odor and slimy consistency. In fungal rots, the odor is usually weak or absent.
• From physiological necrosis: In necrosis, the tissue does not rot and has no odor.

Causes and development conditions: Bacteria causing soft rots live in the soil, on plant debris, and enter the plant through wounds and damage. Warm (+20...+30°C) and humid weather favors development (Akhatov et al., 2013). Overwatering, overfeeding with nitrogen fertilizers, and weakened plants also contribute to infection.

What to do:

1. Preventing damage: Careful handling of plants and protection from pests and diseases that create wounds.

2. Balanced nutrition: Do not apply excess nitrogen, which makes tissues more succulent and vulnerable to bacteria.

3. Proper irrigation: Avoid overwatering and water stagnation. Water at the root, not by overhead irrigation.

4. Storage: Store only healthy, undamaged heads. Maintain optimal temperature and humidity.

6.4. Secondary Infections and Physiological Disorders

Often, rots on the inflorescence are a consequence of not one but several problems. For example, gray mold may first develop on a damaged area, then bacteria join, and the rotting process accelerates. Or conversely, overripening of the head (when buds begin to open and turn yellow) makes tissues more vulnerable to fungal infections.

There is also a specific problem — head rot (or "cabbage head rot"), which is often associated with insect damage to the head or overwatering. The symptoms are similar to bacterial rot, but are often accompanied by specific signs of damage (caterpillar tunnels, frass).

How to distinguish physiological problems from diseases:

• Overripening: The head turns yellow, buds open, but there is no coating, slime, or odor.
• Thermal burn: Tissues become dry, yellow or brown, without signs of decay.
• Boron deficiency: The head may be deformed, with cracks and dark areas, but without putrefactive changes (Basics of Broccoli Production, 2024).

6.5. Prevention of Inflorescence Diseases — The Main Strategy

As can be seen from the description, it is practically impossible to treat rots on broccoli inflorescences. Therefore, all protection is built on prevention:

1. Timing and variety selection: Plant broccoli at optimal times so that heads form and mature during the period with the most favorable weather conditions (without prolonged rains and high humidity). Use disease-resistant hybrids.

2. Balanced nutrition: Avoid excess nitrogen, which makes tissues loose and watery. Apply sufficient potassium and calcium, which increase the strength of cell walls.

3. Pest protection: Timely control of caterpillars and other pests prevents wounds on the head.

4. Proper irrigation: Water at the root, avoiding water getting on the inflorescences.

5. Timely harvesting: Harvest broccoli on time, avoiding overripening. Harvest in dry weather, trying not to damage the heads.

6. Rapid cooling: After harvest, immediately cool the heads to storage temperature to slow down respiration and aging processes that make tissues more vulnerable.

7.1. The Golden Hour: Leaf Diseases at an Early Stage

This is the case when you have a real chance to stop the spread of infection and save the harvest. Leaves are a peripheral organ, and if the disease has not spread to the conducting system, control can be successful.

When you can stop: When you notice the first single spots on a small number of lower or old leaves. The disease has not yet developed into a large-scale epidemic, and the pathogen has not penetrated deep into the tissues.

Which diseases: Alternaria, downy mildew, bacterial spots at early stages.

What to do:

1. Immediate removal: Carefully pick and destroy (burn or remove from the area) all affected leaves. This reduces the amount of infectious material.

2. Preventive treatment: Treat the remaining healthy plants with an approved fungicide or biological product. The choice of product depends on the pathogen (copper-based products work against bacteria and many fungi; biological products based on Bacillus subtilis or Trichoderma are good for prevention).

3. Adjustment of agronomic practices: Think about what could have triggered the outbreak. Perhaps you overwatered the soil, planted too densely, or there was rainy weather. Try to ensure better ventilation (thin the plants if possible) and temporarily reduce watering.

Why this works: By removing affected leaves, you interrupt the pathogen's reproduction cycle. Treatment creates a protective barrier on healthy tissues. Adjusting growing conditions makes the environment less favorable for disease development.

7.2. The Alarm Bell: Beginning of Stem or Root Collar Damage

If the disease has spread from the leaves to the stem, petioles, or root collar, the situation becomes critical. The conducting vessels have already begun to be affected, and it is most likely impossible to cure the plant. But you can still prevent the loss of neighboring plants.

When there is still a chance: When you notice single plants with signs of stem or root collar damage, while the others look healthy.

Which diseases: Rhizoctonia, Fusarium, vascular bacteriosis at the initial stage, when the infection has just begun to penetrate the vessels.

What to do:

1. Radical removal: Immediately dig up the diseased plant along with its roots and a clump of soil around it. Destroy it (burn or bury deep outside the area).

2. Disinfection of the site: Drench the place where the diseased plant grew with a strong solution of potassium permanganate or copper sulfate to destroy the pathogen in the soil.

3. Treatment of neighbors: Treat the remaining plants in this row and adjacent rows with a fungicide or biological product as a preventive measure.

4. Enhanced monitoring: Carefully inspect neighboring plants over the next 1-2 weeks to detect new outbreaks in time.

Why this works: At this stage, saving the diseased plant is no longer possible — the process of vascular clogging is irreversible. Your task is not to allow the infection to spread to healthy plants. Removing the source of infection and disinfection is a standard quarantine procedure that works almost always.

7.3. Hopeless Case: Advanced Damage, Wilting, and Root Diseases

If you see that the plant is wilting en masse, turning yellow, and there are swellings on the roots (clubroot) or they have rotted — it is already too late to save it. You can only minimize the consequences.

When control is useless: In case of severe damage to the vascular system (more than half of the leaves have turned yellow and wilted), with clubroot infection (swellings on roots), with deep rots of stem and roots.

Which diseases: Clubroot, advanced Fusarium, advanced vascular bacteriosis, white and gray molds affecting the central stem.

What to do:

1. Removal of the whole plant: Dig up and destroy the diseased plant along with a large clump of soil around the roots. This is especially important for clubroot, as fungal spores are present in root exudates.

2. Treatment of the hole: Drench the removal site with a disinfectant solution.

3. Situation analysis: Remember this place. Next season, brassicas cannot be planted here.

4. Strengthened prevention on the remaining area: Treat healthy plants and continue to watch them closely.

Why this works: In this case, you have nothing to lose, as the plant is doomed. Your task is not to let the disease spread to neighboring plants and not to allow the pathogen to accumulate in the soil.

7.4. Practical Criteria for Decision Making

How to make the right decision quickly? Here is a simple algorithm:

Ask yourself three questions:

1. Where is the focus of damage? If it's only on the leaves — there's a chance. If it's on the stem or roots — there's almost no chance.

2. What is the extent of damage? If there are a few spots on the leaves — you can fight. If the leaves are yellowing and wilting en masse — the plant is finished.

3. Can the affected part be removed without losing the whole plant? If yes (e.g., remove one diseased leaf) — fight. If the affected part is the center of the rosette or the root — remove the whole plant.

The main rule: It's better to remove one suspicious plant than to risk the entire harvest. This is not cruelty but a reasonable necessity. One diseased bush can become a source of infection for dozens of healthy ones.

7.5. Summary Table for Quick Decision Making

Important addition: The earlier you notice the problem, the greater the chance of success. Daily inspection of plantings is that small investment of time that can save you weeks of labor and save your harvest. Especially carefully inspect plants after prolonged rains, during head formation, and during sharp temperature changes.

8.1. Crop Rotation: The Foundation of All

This is the most powerful and reliable prevention tool. Many pathogens (clubroot, Fusarium, Rhizoctonia) live in the soil for years and accumulate with continuous cultivation of brassicas (Teverson, 2020; Startsev, 2021). Clubroot spores can remain viable for up to 15-20 years, and Fusarium fungus for more than 5 years (Akhatov et al., 2013).

• Rule: Do not return broccoli and other brassicas to the same place earlier than after 3-4 years, and with severe clubroot infection — after 5-7 years.
• Why this works: A break in growing host plants deprives pathogens of a food source. Spores in the soil gradually lose viability, and their numbers decrease.
• Practical tip: Keep a plan of your plot and record where and what you planted. This will help you not forget the rules of crop rotation. Good preceding crops for broccoli are potatoes, onions, legumes, root vegetables (carrots, beets). Bad ones are any brassicas (cabbage, radish, turnip, mustard) (Startsev, 2021).

8.2. Healthy Planting Material: Cleanliness is the Key to Success

Seeds and seedlings are the main routes for infection to enter your plot. Vascular bacteriosis, Alternaria, downy mildew, and even viruses can be transmitted with seeds (Teverson, 2020; Akhatov et al., 2013).

• Rule 1: Buy tested seeds. Purchase seeds only from reliable suppliers who conduct pathogen testing.
• Rule 2: Disinfect seeds. If you use seeds from your own plot or doubt their quality, carry out heat treatment: soak them in hot water (+50°C) for 20 minutes, then immediately cool in cold water (Basics of Broccoli Production, 2024). Important: this can only be done with untreated, uncoated seeds. Chemically treated, coated, or primed seeds cannot be subjected to heat treatment, as this may reduce their germination.
• Rule 3: Use quality seedling soil. The soil for seedlings must be clean, free from clubroot spores and damping-off pathogens. Purchased soil from trusted producers is usually safe. If you use your own soil, it needs to be disinfected (steamed or drenched with biological products).
• Rule 4: Inspect seedlings. Before transplanting into the open ground, carefully inspect each plant. Remove all specimens with signs of disease or damage.

8.3. Optimizing Growing Conditions: Creating Comfort

A healthy, strong plant resists diseases much better than a weakened one. Therefore, your task is to create the most favorable conditions for broccoli.

Proper watering:

• How: Water rarely but deeply, wetting the soil to the root depth (20-30 cm). The best way is drip irrigation or furrow irrigation.
• Why: Such watering does not create waterlogging and does not promote the development of fungal diseases. Also, it stimulates the growth of a deep, powerful root system.
• What to avoid: Frequent surface watering that wets only the top layer. This provokes the growth of shallow roots and creates ideal conditions for the development of Pythium and Rhizoctonia. Also avoid getting water on leaves and heads, especially in the evening (Teverson, 2020; Basics of Broccoli Production, 2024).

Balanced nutrition:

• Nitrogen: Excess nitrogen makes tissues loose and watery, which increases susceptibility to bacterial and fungal rots. Apply nitrogen in fractions, in moderate doses (125-175 kg/ha in terms of active ingredient) (Basics of Broccoli Production, 2024).
• Potassium and calcium: These elements strengthen cell walls, making plants more resistant to mechanical damage and pathogen penetration. Calcium also reduces susceptibility to clubroot (Teverson, 2020).
• Microelements: Broccoli is particularly sensitive to boron and molybdenum deficiency. Boron deficiency makes plants more susceptible to rots (Basics of Broccoli Production, 2024).

Proper planting pattern:

• How: Maintain recommended distances between plants (in-row 15-30 cm, between rows 60-90 cm, depending on the variety and growing system) (Basics of Broccoli Production, 2024).
• Why: Dense plantings create stagnant humid air, which is ideal for fungal development (Alternaria, downy mildew, gray mold). Additionally, overcrowding leads to competition for light and nutrition, weakening plants.

Soil pH control:

• How: Maintain soil pH at 6.5-7.0 (Basics of Broccoli Production, 2024).
• Why: Acidic soil (pH below 6.0) promotes the development of clubroot and damping-off (Teverson, 2020). Liming not only reduces acidity but also improves soil structure.

Optimal planting time:

• How: Plant seedlings at the optimal time for your region so that the head formation period falls in cooler and drier weather.
• Why: This allows plants to "escape" the peak activity of many pathogens. For example, early planting helps avoid Fusarium, which is most active in heat (Startsev, 2021). At the same time, very early planting can lead to plants being hit by frost and weakened.

8.4. Hygiene: Sanitary Treatment of the Plot and Equipment

Infection spreads not only by air and water but also through hands, footwear, tools, plant debris, and contaminated soil.

Clean tools: Wash and disinfect garden tools (shovels, hoes, pruners) after working on the plot, especially if you have noticed diseased plants. Use soap, potassium permanganate solution, or special disinfectants.

Footwear and clothing: Dirt on shoes is one of the main ways of spreading clubroot spores and other soil-borne pathogens. Wash shoes when moving from one area to another.

Plant debris: Thoroughly collect and destroy all plant debris after harvest. Incorporate it into the soil (if healthy) or burn it (if diseased). Do not leave diseased leaves and stems on the beds — pathogens will overwinter on them (Teverson, 2020).

Clean seedling boxes: Seedling trays and boxes must be washed and disinfected after each use. This prevents the transmission of damping-off and other pathogens from one season to the next (Teverson, 2020; Akhatov et al., 2013).

8.5. Use of Resistant Varieties and Biological Products

Resistant varieties: This is your reliable shield. Many modern broccoli hybrids have genetic resistance to Fusarium, clubroot, vascular bacteriosis, and other diseases. When buying seeds, pay attention to this characteristic (often indicated on the packaging or in the catalog). Resistance does not guarantee 100% protection but significantly reduces the risk of crop loss (Teverson, 2020; Akhatov et al., 2013).

Biological products: These are environmentally safe plant protection products that work for prevention. They contain living microorganisms (e.g., Bacillus subtilis or Trichoderma) that suppress pathogen development or stimulate plant immunity.

• How to use: Apply biological products to the soil during planting, water seedlings with them, spray plants during the growing season (especially before rains).
• Why this works: Biological products create a protective screen of beneficial bacteria around the roots, competing with pathogens for nutrients and space. They can also enhance the defensive reactions of the plants themselves.

8.6. Monitoring and Regular Inspection

This is a simple but critically important habit.

How: Walk through your plot at least 2-3 times a week, especially in damp and warm weather. Carefully inspect leaves, stems, root collars (you can gently scrape away soil at the base of the plant). Pay attention to changes in color, wilting, spots, coatings.

Why: The earlier you notice a problem, the easier it will be to deal with it. Daily inspection is your "early warning system" that gives you a chance for success.

Special attention: Pay particular attention to areas with drainage problems, field edges, and places at the entrance (where dirt is more often brought in). Also carefully inspect plants during prolonged rains, heavy dews, and after sharp temperature changes (Teverson, 2020).

8.7. Summary Table: A Systemic Approach to Prevention