Dogwood anthracnose

Dogwood anthracnose is a destructive plant disease caused by the fungus Discula destructiva. This pathogen is highly specific to certain dogwood species and is known for causing severe decline and mortality in vulnerable landscape trees. It represents a significant threat to both ornamental gardens and forest ecosystems where susceptible species are present.

The primary hosts of this pathogen are Cornus florida and Cornus kousa. The fungus attacks all parts of the plant, including leaves, twigs, and main branches. Infection often begins in the lower canopy, as the fungus thrives in the humid, shaded conditions typically found near the ground, before gradually spreading throughout the entire tree structure.

Symptoms of the disease include tan, circular or irregular leaf spots with distinct purple-red margins. If left untreated, the infection moves from the leaves into the twigs, causing dieback and the development of cankers on branches. These cankers interrupt nutrient and water transport, eventually causing the death of the limb or the entire host plant.

The spread of Discula destructiva is highly dependent on environmental conditions, particularly extended periods of rainfall, high humidity, and cool temperatures. Splashing water from irrigation or rainfall effectively spreads the fungal spores to healthy tissue. Dense planting and poor airflow within the tree canopy significantly increase the severity of an outbreak.

Effective management requires a combination of cultural and chemical control measures. Key strategies include:

• Removing and destroying infected twigs and branches.
• Pruning to improve airflow and sunlight penetration.
• Mulching around the base to prevent soil-borne spores from splashing onto foliage.
• Applying systemic fungicides during the early leaf expansion period.
• Selecting resistant dogwood cultivars for new plantings.