Anthracnose
Colletotrichum acutatum complex (C
180 host plants · Fungal
Last updated
Watch for small, round spots with dark centers appearing on foliage, particularly on dogwoods, oaks, and maples during wet springs. Infected leaves develop gray or black centers with a distinct border; under humid conditions, you might spot pinkish spore masses within lesions. More concerning are lesions on leaf stems and petioles that can girdle and kill entire leaves, or crown rot starting from the base of plants where the tissue turns reddish-brown and soft. The disease accelerates when conditions stay wet for extended periods, which is typical in cool climates during spring.
Anthracnose thrives in cool, wet conditions that favor spore germination and spread. Continuous wetness for 8 hours or longer creates ideal conditions for infection, and high nitrogen fertility actually increases disease severity by promoting succulent growth. The key to management is reducing leaf wetness and improving air circulation around your plants. Space trees and shrubs to allow foliage to dry quickly after rain and irrigation; use drip irrigation rather than overhead watering; prune off infected branches and twigs during dormancy, before new inoculum works into the soil; and select resistant cultivars when available, such as Kousa dogwood selections like Stellar Pink or Celestial.
Quick Reference
Management
Growing season; young foliage, open flowers, and ripening fruit most susceptible; winter survival in infected debris.
Conditions vary by causal agent. Shade tree anthracnose (Discula destructiva on dogwood, Apiognomonia spp. on sycamore/oak/maple): cool temperatures (50-57°F optimal during bud break and early leaf development) with prolonged leaf wetness (12+ hours continuous). Colletotrichum spp. (strawberry, bramble, agricultural hosts): warmer temperatures favoring sporulation (above 68°F optimal) with 8+ hours leaf wetness; high humidity during flowering and fruit ripening. All forms require free moisture on plant surfaces for spore germination.
Cultural Controls
- Use certified planting stock.
- Rake and destroy fallen leaves from spring through fall to reduce overwintering inoculum.
- Prune out and destroy infected twigs and branches during dormancy.
- Increase spacing and maintain open canopy structure for air circulation.
- Avoid overhead irrigation, or limit the time plants are wet from irrigation.
Shade tree anthracnose (dogwood, maple, sycamore forms) is common in this region due to cool, wet springs with prolonged leaf wetness during bud break. Sycamore anthracnose is especially conspicuous in years with cool May weather. Dogwood anthracnose (Discula destructiva) is a serious concern on native Pacific dogwood (Cornus nuttallii); kousa dogwoods and kousa hybrids show strong resistance. Strawberry/bramble anthracnose (Colletotrichum spp.) is less prominent here than in warmer production regions but can affect home fruit plantings during warm wet periods.