Anthracnose
Fraxinus velutina
What is Anthracnose (Apiognomonia errabunda)?
Anthracnose, caused by the fungal pathogen Apiognomonia errabunda (Discula quercina), affects various oak species, including black oak, white oak, northern red oak, pin oak, chestnut oak, scarlet oak, and swamp white oak. It has a wide distribution and can be found in different regions. Symptoms include water-soaked, blighted leaf margins or blotches along veins on new foliage, which turn dry, papery, and gray over time. Distorted or shriveled leaves may be shed prematurely. Twig infections can also occur, leading to branch dieback. Anthracnose poses a significant threat to trees in affected areas.
How does Anthracnose (Apiognomonia errabunda) occur?
The disease spreads through the release of spores primarily dispersed by wind and rainwater. Wet weather conditions during the early growing season create favorable conditions for infection. The fungus forms lesions on leaves and twigs, leading to blighted leaf margins, discoloration, and twig dieback. In severe cases, defoliation can occur. The pathogen can overwinter in resting structures and continues to infect new foliage in the following spring, perpetuating the cycle of the disease.
Symptoms
1 - Plants Health
• Severe infections of Apiognomonia errabunda can lead to premature shedding of leaves, impacting the overall health and growth of trees. • The disease can cause the death of twigs, resulting in reduced canopy density and potential structural weakness.
2 - Soil Health
• Defoliation and twig dieback can affect nutrient cycling in the soil as fallen leaves and twigs decompose more slowly. • The presence of the fungal pathogen may influence soil microbial communities and their functions.
3 - Impacts on the Environment
• Impact of anthracnose can affect biodiversity by reducing the health and vitality of populations. • Weakened or dead trees may contribute less to carbon sequestration, potentially affecting the ecosystem's ability to mitigate climate change.
Solutions
1 - Cultural Practices
Maintain overall tree health through regular pruning, removal of dead branches, and appropriate watering and fertilization practices. • Remove and destroy fallen leaves and infected plant debris to reduce the potential for fungal spores to spread. • Selecting and planting tree varieties that are known to exhibit resistance to anthracnose can reduce the risk of infection.
2 - Site Selection and Regular Monitoring
• Plant trees in locations that provide good air circulation and adequate sunlight, as this can help prevent prolonged leaf wetness and reduce fungal growth. • Monitor trees for early signs of infection, such as leaf discoloration or lesions. Prompt detection allows for timely treatment and prevents further spread.
3 - Chemical Control
• Fungicides: In severe cases or for high-value trees, apply fungicides labeled for anthracnose, Chlorothalonil, propiconazole, and thiophanate-methyl are commonly used fungicides for anthracnose control. • Consult with a certified arborist or horticulturist to determine the appropriate fungicide and application timing.
