Tree Cankers

Tree cankers are localized areas of dead tissue on trees, often caused by various fungal, bacterial, or environmental factors. Cankers can lead to significant damage if not managed properly, affecting the health and structural integrity of the tree.

Characteristics of Tree Cankers

1. Appearance
   • Shape and Size: Cankers can vary in shape and size, often appearing as sunken, discolored, or cracked areas on the bark. They may be round, irregular, or elongated.
   • Color: The color of cankers can range from dark brown or black to gray or reddish, depending on the pathogen involved.
   • Texture: The affected area may be dry and cracked or wet and oozy, depending on the type of canker.
2. Symptoms
   • Bark Damage: Cankers often lead to loss of bark, exposing the inner wood. This can result in girdling of the tree, affecting its nutrient and water transport.
   • Dieback: Branches or limbs above the canker may show signs of dieback or leaf drop due to reduced vascular function.
   • Exudates: Some cankers produce ooze or resin that may be visible on the surface of the affected area.

Causes of Tree Cankers

1. Fungal Diseases
   • Cytospora Canker: Caused by Cytospora spp., this canker affects many tree species, leading to sunken lesions and bark splitting.
   • Sooty Canker: Caused by Pseudomonas syringae, it often appears as dark, sunken areas on the bark, particularly in stressed or wounded trees.
2. Bacterial Diseases
   • Fire Blight: Caused by Erwinia amylovora, primarily affects fruit trees like apples and pears, causing blackened, sunken cankers and dieback.
   • Bacterial Canker: Caused by Clavibacter michiganensis, this canker affects tomatoes and other plants, producing sunken lesions with dark margins.
3. Environmental Stress
   • Physical Injury: Mechanical damage from tools, animals, or storms can create wounds that become entry points for pathogens, leading to cankers.
   • Drought Stress: Prolonged drought can weaken trees, making them more susceptible to cankers and other diseases.
4. Insect Damage
   • Boring Insects: Certain insects, like bark beetles or wood borers, can create wounds or galleries in the bark, leading to secondary infection and canker formation.

Management Strategies

1. Disease Control
   • Pruning: Remove infected branches or limbs below the canker to prevent the spread of disease. Disinfect pruning tools between cuts to avoid cross-contamination.
   • Fungicides/Bactericides: Apply appropriate fungicides or bactericides based on the specific pathogen. Follow label instructions for application and timing.
2. Environmental Management
   • Avoid Wounding: Take precautions to prevent physical damage to trees, such as using proper equipment and avoiding activities that may injure the tree.
   • Watering: Ensure trees receive adequate water, especially during dry periods, to help reduce stress and improve overall health.
3. Insect Control
   • Monitoring: Regularly inspect trees for signs of insect infestations. Use integrated pest management (IPM) techniques to control insect populations and reduce the risk of canker development.
4. Cultural Practices
   • Tree Health: Maintain overall tree health through proper planting, mulching, and fertilization practices. Healthy trees are more resistant to cankers and other diseases.
   • Site Selection: Plant trees in suitable locations with well-drained soil and adequate sunlight to reduce environmental stress.
5. Sanitation
   • Remove Debris: Clean up fallen branches and leaves around trees to reduce the potential for pathogen buildup and spread.
   • Dispose of Infected Material: Properly dispose of infected plant material to prevent the spread of disease.

Prevention

1. Resistant Varieties: Choose tree species or varieties that are resistant to common canker pathogens when planting new trees.
2. Regular Inspections: Conduct regular inspections of trees for early signs of cankers and address issues promptly to prevent further spread.