Causal Agents:
The disease is caused by several fungi, with the genus Colletotrichum being one of the most common culprits. Other genera like Gloeosporium and Diseula can also be responsible, depending on the host plant.
Symptoms:
- Leaves: Small, irregular, water-soaked spots appear initially. These spots darken as they age and may merge, forming larger dead areas. In some cases, there's a pronounced vein-delimited pattern.
- Fruits: Dark, sunken lesions. On vegetables like tomatoes, it manifests as sunken, circular spots.
- Twigs and Branches: It can cause dieback, with young twigs being particularly susceptible. Cankers (dark sunken areas) may form on stems.
- Flowers: Blight or withering of flowers.
Host Plants: Anthracnose affects a wide range of plants. Trees commonly affected include oak, maple, ash, walnut, sycamore, and dogwood. In the realm of fruits and vegetables, it affects strawberries, tomatoes, beans, and cucumbers, among others.
Mode of Spread:
- Rain and Water: The fungus produces spores in the infected tissue, which can be splashed by rain or irrigation onto other plants.
- Garden Tools: Pruning or gardening tools that aren't properly cleaned can spread the disease.
- Infected Plant Debris: Leaves or fruits that have fallen to the ground can be a source of the fungus for the next season.
Management and Control:
- Cultural Practices: Regularly inspect plants and remove infected parts. Clean up and dispose of fallen leaves and fruits to reduce the source of infection.
- Resistant Varieties: Some plant varieties or species are resistant or less susceptible to anthracnose. Choosing them can reduce the chances of disease.
- Watering: Water plants at the base rather than overhead to reduce the chance of spore splash. Also, watering in the morning allows leaves to dry out during the day.
- Fungicides: For severe or persistent cases, fungicides can be applied. Always follow label recommendations and consult local agricultural extensions for guidance specific to the region and plant.
- Proper Spacing: Ensure plants have adequate spacing to reduce humidity around them, making conditions less favorable for the fungus.
- Tool Hygiene: Always sterilize gardening tools, especially if used on infected plants.
Impact: Anthracnose can reduce the aesthetic value of ornamental plants. In severe cases, it can lead to significant defoliation and dieback in trees. For fruit and vegetable growers, it can reduce yields and the marketability of the produce.
Prevention: The key to managing anthracnose lies in prevention. Regular inspection, proper cultural practices, and maintaining good garden hygiene can significantly reduce the impact of this disease.