Anthracnose (Medynka)

Anthracnose is a group of fungal diseases in plants caused by pathogenic fungi of the genus Colletotrichum and other members of the Glomerellaceae family. The disease affects a wide range of agricultural crops, ornamental, and garden plants. Anthracnose is characterized by the formation of spots and ulcers on leaves, stems, flowers, and fruits, leading to reduced yield, deterioration of plant appearance, and, in some cases, plant death. One of the most common types of anthracnose is Medynka, which affects many plant species, including tomatoes, potatoes, beans, grapes, as well as ornamental trees and shrubs.

This article discusses the main aspects of anthracnose, its signs and symptoms, causes, diagnostic methods, control strategies, prevention methods, and specific recommendations for various types of plants.

Importance of the Topic

Knowledge of anthracnose is crucial for houseplant and agricultural crop owners. Anthracnose can cause serious plant damage, reducing both their ornamental and productive qualities, and in some cases, leading to the plant's complete death. Understanding the mechanisms of anthracnose's occurrence and spread allows for effective disease management, minimizing damage and maintaining plant health. This knowledge is especially important for houseplant owners who often lack sufficient knowledge and resources to combat fungal infections such as anthracnose.

Objectives of the Article

The purpose of this article is to provide comprehensive information about anthracnose, including its signs, causes, diagnostic methods, and control strategies. The reader will learn:

• The signs and symptoms of anthracnose.
• The factors contributing to the development of this disease.
• How to properly diagnose anthracnose and distinguish it from other diseases.
• The most effective methods for control and prevention.
• Specific recommendations for different types of plants.
• When and how to seek professional help.

Signs and Symptoms of Plant Disease

Spots on Leaves

• One of the most characteristic signs of anthracnose is the formation of dark or brown spots with clear borders on the leaves. These spots usually have a light or yellowish surrounding.
• The spots can be round or irregular in shape and grow larger over time. Small black dots can be seen on the surface of the spots, which are the fungal fruiting bodies that serve for reproduction.
• It is important to note that these spots can appear not only on leaves but also on stems, flowers, or fruits.

Yellowing and Chlorosis

• Chlorosis (yellowing) can develop around the affected tissue, which is associated with a disruption in the normal metabolic and photosynthetic activity.
• Leaves around the spots turn yellow, indicating the breakdown of chlorophyll, which is necessary for photosynthesis.

Fruit and Berry Rot

• On the fruits of infected plants, anthracnose appears as dark, watery spots that gradually spread, causing the fruit to rot.
• Over time, these fruits become soft, may begin to decay, and lose their nutritional value. Small, dark dents may appear on berries, which eventually expand into large areas of rot.

Rot and Bark Damage

• On plant stems and branches, ulcers and wounds may form, which become entry points for the fungi. Such damage can lead to tissue necrosis and the death of stem sections.
• Sometimes anthracnose can damage the bark, weakening the plant and disrupting its normal development.

Leaf Drop

• In severe cases of the disease, leaves may prematurely fall off, weakening the plant, reducing its photosynthetic activity, and promoting further spread of the infection.

Rapid Wilting of Plants

• Infected plants begin to wilt because the fungus destroys the vascular system, disrupting water exchange and the delivery of nutrients. As a result, the plant appears weakened, its growth slows, and fruits and flowers become smaller and poorly developed.

Causes of Plant Disease

The pathogens of anthracnose are fungi belonging to the genus Colletotrichum (e.g., Colletotrichum coccodes, Colletotrichum gloeosporioides) and other genera such as Glomerella, Gnomonia, and Guignardia. These fungi can survive in plant debris, on infected plant parts, and in seeds. They can persist in soil and on plant residues as spores and mycelium, which allows them to withstand adverse conditions and reinitiate infection in subsequent seasons.
The spores of anthracnose are spread by wind, rain, water droplets, and infected tools. They can travel over long distances, especially in high humidity and optimal temperatures for fungal growth. The infection typically starts on the surface of leaves or fruits, where the spores germinate and penetrate plant tissues.

Life cycle of anthracnose in plants

The life cycle of fungi from the genus Colletotrichum, which cause anthracnose in plants, includes several stages during which the fungus spreads and infects various parts of the plant, including leaves, stems, fruits, and roots. The life cycle of anthracnose is complex and can vary depending on the plant type and environmental conditions. The main stages of the anthracnose life cycle include:

1. Overwintering Structures (Sclerotia, Conidia)
   The Colletotrichum fungus can overwinter in the form of various structures such as:
   • Sclerotia — dense, dark structures formed in plant debris or soil, which can persist for several months or even years.
   • Conidia — microscopic spores that typically form on infected parts of the plant, such as leaves or fruits. These conidia can survive in plant residues and soil during winter.
2. Germination of Conidia
   In spring or summer, when the weather conditions become more favorable (increased temperature and humidity), conidia begin to germinate. The germination process includes the following steps:
   • Conidia, landing on the moist surface of the plant, start to germinate and form a special structure called a conidiophore, which releases new spores.
   • These spores can penetrate plant tissues by entering through stomata, wounds, or damaged areas.
3. Through plant tissues — the mycelium grows within the tissue, breaking down cell walls and extracting nutrients, which leads to the formation of characteristic necrotic spots on leaves, stems, and fruits.
   • Affected tissues become soft and watery, contributing to rotting.
4. Ascospores — spores formed within the fruiting bodies of the fungus (ascosporic structures). Ascospores are a sexual reproduction stage and can be ejected into the surrounding environment.
5. Conidia — vegetative spores that form abundantly on the surface of infected tissues, such as leaves, stems, or fruits. Conidia are the primary agents of vegetative reproduction and can be carried by wind, rain, or insects to other plants, infecting them.
6. Transmission: Conidia spread across plants by wind, raindrops, mechanical impacts, or with the help of pests like aphids. This allows the pathogen to rapidly spread across an infected area or even over large distances.
7. Infection: When spores land on new plants, especially under high humidity and warm weather, they begin to germinate and infect the plants, starting a new cycle of infection.
   • When the plant tissues finally die due to the action of the fungal mycelium, new spores (conidia) form on the surface, which can fall into the soil or onto plant residues. These spores overwinter in the soil or on plant debris, ensuring the persistence of the infection until the next season.
8. Invasion and Mycelial Growth
   After conidia germinate, the fungal mycelium begins to spread through the plant, infiltrating cells and tissues. The mycelium spreads in the following directions:
9. Formation of Fruiting Bodies and Spores (Ascospores and Conidia)
   As the fungus grows, it forms two types of spores:
10. Transmission of Infection
11. Completion of the Cycle and Return to Soil

Influence of weather conditions on the life cycle

The life cycle of anthracnose is closely linked to climatic conditions. The optimal conditions for the development of Colletotrichum include:

• Temperature: Typically, temperatures between 20°C and 30°C are ideal for fungal growth.
• Humidity: High humidity and rainfall promote the development and spread of the disease, as fungal spores germinate and infect plants in humid conditions.
• Weather Conditions: Humidity and temperature play a key role in how quickly the fungus will spread. Dry conditions may slow the infection process, but during rainy periods, the fungus reproduces rapidly.

Conditions for Disease Development

Anthracnose prefers a warm and humid environment. The optimal temperature for disease development is between 20°C and 30°C, with temperatures above 35°C slowing fungal growth. Humidity plays a crucial role in the spread of infection: with high humidity, especially in conditions of rain or dew, fungal spores germinate rapidly and infect plants. Low temperatures or dry conditions may slow anthracnose development, but do not eliminate the risk of infection.

Older and damaged plants are more susceptible to anthracnose, as their immune systems are weakened, creating favorable conditions for fungi. Increased planting density and poor ventilation also contribute to infection spread.

Impact on Plants

Anthracnose has a destructive effect on plants, leading to:

1. Reduced Yield: On agricultural crops, anthracnose reduces the quality and quantity of the harvest. This is especially important for fruit crops, as the disease causes premature fruit drop and reduces their marketability.
2. Plant Weakening: The infection disrupts normal photosynthesis, affecting plant growth and development. Weakened plants become more vulnerable to other diseases and environmental stresses.
3. Degradation of Ornamental Plants: In ornamental plants, anthracnose can lead to the loss of aesthetic qualities, especially for those used in landscape design.
4. Plant Death: In severe cases, especially on stems and roots, the plant can be completely destroyed.

Diagnosis of Plant Disease

Diagnosis of anthracnose caused by Colletotrichum fungi relies on recognizing characteristic symptoms on plants, as well as using microscopic and laboratory methods to accurately identify the pathogen. Timely diagnosis is important to take effective control measures, minimize damage, and prevent its spread.

1. Visual Diagnosis

The primary method for diagnosing anthracnose is a careful visual inspection of the plants for the presence of characteristic signs of the disease:

• Spots on Leaves
  One of the most characteristic signs of anthracnose is dark or brown spots on leaves. These spots usually have clear borders and can be round or irregular in shape. In the center of the spots, black dots can be seen, which are the fruiting bodies of the fungus, a distinguishing feature of anthracnose.
  The spots typically have a yellow or light-colored border and can enlarge over time.
• Yellowing (Chlorosis) of Tissue Around Spots
  Chlorosis (yellowing) around the affected tissue is linked to a disruption in normal metabolic processes in the affected areas of the plant. Chlorosis may spread across the whole leaf surface, not just around the spots.
• Fruit Damage
  On fruits and berries, anthracnose manifests as small dark or brown spots that grow over time and can cause the fruit to rot. These spots are usually watery, and in more advanced stages, the fruits become soft, break down, and lose their nutritional value.
• Rot on Stems and Bark
  The fungus can affect not only leaves but also stems or bark. In this case, ulcers or wounds form on the affected areas, which gradually enlarge. These damages are often accompanied by tissue deformation and decay, potentially leading to the death of the stem.
• Premature Leaf Drop
  In severe cases, anthracnose can cause premature leaf drop, weakening the plant by removing its photosynthetic surface.

2. Microscopic Diagnosis

To confirm the diagnosis, microscopy is used. About 2-3 weeks after infection, the characteristic fruiting bodies of the fungus may appear on the affected leaves, stems, or fruits.

• Finding Fruiting Bodies of the Fungus
  Inside the affected tissues, black dots, which are conidiophores, can be found. These structures bear new spores (conidia), and these spores can be easily observed under a microscope.
• Observing the Structure of the Fungus
  Colletotrichum fungi form characteristic structures: multicellular ascospores and conidia, which, under a microscope, appear as long threads. Conidia are the vegetative spores that actively spread via water droplets or wind currents.

3. Laboratory Methods

For accurate identification of the anthracnose pathogen, laboratory methods can be employed:

• Fungal Cultivation
  The fungus can be isolated from the infected tissue and cultured on nutrient media. After incubation, typical fungal colonies will form. This method helps not only to confirm the diagnosis but also to accurately identify the species of the fungus causing anthracnose.
• PCR (Polymerase Chain Reaction)
  Molecular methods such as PCR allow for the accurate identification of Colletotrichum, the pathogen of anthracnose. This method can detect the fungus' DNA even in cases where visual symptoms are not yet expressed, which aids in early diagnosis.
• Serological Tests
  Serological tests, such as enzyme-linked immunosorbent assay (ELISA), can detect antibodies against Colletotrichum in plant tissues. These tests allow for rapid disease diagnosis, especially when the infection's later-stage signs are present.

4. Differential Diagnosis

For accurate diagnosis, it is important to rule out other diseases that may exhibit similar symptoms:

• Phytophthora (Phytophthora)
  Unlike anthracnose, phytophthora causes the softening of tissues and the appearance of wet, soft spots with diffuse borders. The spots are usually moist and watery, and they most commonly affect stems, fruits, and roots.
• Fusarium Wilt
  Fusarium wilt symptoms are more pronounced on stems and roots rather than on leaves. This disease is associated with wilting of the entire plant and disruption of the vascular system, which differs from the localized lesions typical of anthracnose.
• Bacterial Infections
  Bacterial diseases often appear as spots on leaves with diffuse borders. However, bacterial infections usually also involve slimy exudates or an unpleasant odor, which is not present in anthracnose.

Control Methods for Plant Diseases

Treatment of anthracnose involves several stages, from the use of fungicides to agronomic practices aimed at improving growing conditions and preventing the disease.

1. Use of Fungicides

One of the main methods for controlling anthracnose is the use of fungicides, which can effectively suppress fungal growth. Both systemic and contact fungicides are used, depending on the stage of the disease and the type of plant.

• Contact Fungicides
  Contact fungicides act directly on the plant surface without penetrating its tissues. They should be applied before the onset of infection or at the very beginning of symptom appearance.
  Examples of contact fungicides include:
  • Copper-based products (e.g., copper sulfate, Bordeaux mixture).
  • Sulfur (sulfur), which acts as a fungicide and helps reduce infection.
• Systemic Fungicides
  Systemic fungicides penetrate plant tissues and spread through the vascular system, providing protection not only from existing infections but also from reinfection.
  Examples of systemic fungicides include:
  • Azole-based products (e.g., Topsin-M, Diter, Fundazol).
  • Azoxystrobin, which helps control both anthracnose and other fungal infections.

Application Frequency

• Fungicides should be applied as needed, depending on weather conditions and the disease stage. Typically, treatments are done every 7-14 days depending on the type of product and the infection's intensity.
• Treatment should be thorough to cover all leaves and other plant parts exposed to the disease.

2. Removal of Infected Plant Parts

Removing infected leaves, stems, and fruits is a key step in combating anthracnose. This helps reduce the number of spores that can spread to other parts of the plant or to neighboring plants.

• Inspection: Regularly inspect plants for signs of anthracnose (dark spots, rotting fruits and leaves).
• Pruning and Disposal: Infected leaves and fruits should be carefully cut using sterilized scissors or pruning shears.
• Proper Disposal: Removed plant parts should be burned or placed in sealed bags to prevent the spread of spores.

3. Prevention of Excessive Moisture

High humidity contributes to the development of fungal diseases like anthracnose. Therefore, it is essential to reduce humidity in greenhouses or on garden plots to minimize the risk of infection.
Recommendations:

• Improve Ventilation: Ensure adequate air circulation in greenhouses and garden plots. This helps reduce humidity and accelerates drying of leaves after rain or watering.
• Proper Watering: Water plants so that water does not get on the leaves and stems. Drip irrigation or watering at the root is preferred to avoid excess moisture on the plant.
• Maintain Optimal Temperature: Lowering the temperature also helps reduce humidity, especially in enclosed spaces like greenhouses.

4. Use of Biological Preparations

Biological fungicides are an environmentally safe method of controlling anthracnose. These preparations are based on beneficial microorganisms that suppress the growth of pathogenic fungi.
Examples of biological fungicides:

• Trichoderma — a fungus that actively combats many fungal diseases, including anthracnose.
• Bacteria of the Bacillus genus (e.g., Bacillus subtilis), which inhibit the growth of Colletotrichum.

Biological fungicides are effective in combination with other methods, such as improving growing conditions and applying chemical treatments.

5. Fertilization

After a plant has been affected by anthracnose, it may weaken, making recovery difficult. Fertilization plays an important role in speeding up the recovery process.

Fertilization recommendations:

• Nitrogen Fertilizers: Nitrogen fertilization helps plants recover by stimulating the growth of new, healthy tissues.
• Phosphorus-Potassium Fertilizers: These fertilizers strengthen the root system and increase plant resistance to diseases.
• Micronutrients: Additional application of micronutrients (e.g., magnesium, copper) can help improve plant immunity and accelerate recovery.

6. Improvement of Agronomic Conditions

• Crop Rotation: To reduce the likelihood of reinfection, practice crop rotation. Avoid planting crops susceptible to anthracnose in the same location for several consecutive years.
• Removal of Plant Residues: Remove all plant residues from the plot to prevent fungal spores from overwintering in the soil.

Plant Disease Prevention

Prevention of anthracnose is a set of measures aimed at preventing the disease and reducing the risk of infection by Colletotrichum fungi, which cause anthracnose. Effective preventive measures help maintain plant health, improve resistance to fungal diseases, and prevent the spread of infection. Here are the main prevention methods for anthracnose:

1. Selection of Resistant Plant Varieties

• Choosing plant varieties that are resistant to anthracnose is one of the most effective ways to prevent the disease. Some plant varieties, such as certain types of tomatoes, potatoes, and other vegetables, have natural resistance to fungal infections. Choose varieties that are better adapted to local climatic conditions and less susceptible to the disease.

2. Crop Rotation

• Crop rotation helps prevent the accumulation of pathogens in the soil, as Colletotrichum fungi can persist in plant residues and soil. It is not recommended to plant crops susceptible to anthracnose in the same plot for consecutive years.
• Regularly changing planting locations helps reduce the fungal population in the soil and prevents reinfection.

3. Management of Plant Residues

• Removing plant residues from the plot after harvest or pruning helps prevent the accumulation of fungal spores in the soil. All infected plants, fruits, and leaves should be disposed of by burning or placing them in sealed bags to prevent the spread of infection to other plants.

4. Proper Watering and Plant Care

• Root-level watering: To prevent the spread of fungi, avoid overhead watering, as water on the leaves and fruits creates favorable conditions for the spread of spores. It is better to use drip irrigation or water plants at the root level.
• Maintaining Moderate Humidity: High humidity promotes the development of anthracnose, so it is important to control humidity levels in greenhouses and gardens. Problems may arise in poorly ventilated conditions, so regular ventilation helps reduce humidity and prevent the spread of fungal infections.

5. Optimization of Growth Conditions

• Lighting: Providing good lighting and air circulation around plants promotes healthy growth and reduces the risk of infection. Overcrowded plantings with poor ventilation create ideal conditions for the growth of fungi.
• Temperature: Optimal temperature conditions (usually 20–25°C) are also important for preventing anthracnose. High temperatures with high humidity create ideal conditions for the growth of Colletotrichum.

6. Regular Inspection and Monitoring

• Regular plant inspections help detect early signs of the disease. Infected leaves and fruits should be immediately removed to prevent further spread of infection. The earlier measures are taken, the less damage the disease will cause.
• Inspections should be conducted during hot and humid periods when conditions for fungi are most favorable.

7. Use of Fungicides

• Preventive treatment of plants with fungicides helps prevent fungal infection. Both contact and systemic fungicides are used to provide long-term protection. Treatments should be applied before symptoms of the disease appear, especially during periods of high humidity or rainy days when the risk of infection increases.
  Examples of effective fungicides:
  • Copper-based products (e.g., copper sulfate, Bordeaux mixture).
  • Sulfur-based products (sulfur).
  • Systemic fungicides, such as triazoles or azoxystrobin-based products.

8. Use of Biological Agents

• Biological fungicides, based on beneficial microorganisms, can also be used to prevent anthracnose. For example, microorganisms such as Trichoderma suppress fungal growth and prevent their spread. Biological agents are safe for the environment and can be used in organic farming.

9. Cleaning Tools and Equipment

• To prevent transferring fungi to healthy plants, regularly clean and disinfect garden tools such as scissors, pruning shears, shovels, etc. Disinfection solutions such as bleach, alcohol, or other antiseptics can be used for sterilizing tools.

10. Protection Against Pests

• Pests, such as aphids, can be vectors for Colletotrichum spores. Therefore, it is important to control the pest population using insecticides or biological control methods (e.g., with beneficial insects like ladybugs).

Frequently Asked Questions (FAQ)

1. What are the most common plant diseases?
   The most common diseases are anthracnose, powdery mildew, Phytophthora, bacterial burn, and viral infections. Each of these diseases has its specific symptoms and requires different control methods.
2. How to distinguish a disease from a pest?
   Pests usually manifest as insects or their traces on plants, such as sticky honeydew, spots, or webs. Diseases typically show up as spots, wilting, or color changes in leaves without visible insects. If in doubt, it’s advisable to conduct a diagnosis or consult a specialist.
3. Can pests be completely eliminated without chemicals?
   Yes, there are effective organic and natural pest control methods, such as soap solutions, neem oil, garlic infusions, and mechanical pest removal. Combining different methods ensures the best results.
4. How often should plants be treated preventively?
   Regular preventive treatments are recommended every 2-4 weeks, especially during the active growth periods of plants. This helps prevent pests and diseases from appearing.
5. Which plants are most resistant to diseases?
   Some plants, such as Sansevieria, Zamiochulkas, Kalanchoe, and succulents, are highly resistant to diseases due to their tough leaves and ability to withstand adverse conditions. These plants are an excellent choice for those aiming to minimize disease risks.

Final Tips

• Regularly inspect plants: Frequently check plants for signs of diseases and pests, especially during active growth periods.
• Follow sanitation protocols: Keep tools and the surrounding environment clean to prevent pathogen spread.
• Provide balanced care: Ensure optimal watering, lighting, and fertilization conditions to maintain plant health and disease resistance.
• Isolate infected plants: When disease is detected, isolate affected plants to prevent spreading to others.
• Use quality soil mixes: Choose soil that meets your plants' needs and monitor its quality and composition.

By following these recommendations, you can effectively combat anthracnose and other plant diseases, ensuring healthy growth and thriving plants in your home.