Anthracnose: Fungal Leaf & Twig Blight on Trees, Shrubs & Greenhouse Crops

Anthracnose, caused by Colletotrichum, Gloeosporium, Apiognomonia, and related fungi, attacks deciduous/evergreen trees, shrubs, fruits, vegetables, and greenhouse crops in cool, wet spring weather. Dark, sunken lesions on leaves, veins, stems, flowers, and fruit are characteristic. The disease cycles annually but is rarely fatal. Sanitation and plant health are the main controls.

Hosts

• Trees/shrubs: Maple, camellia, walnut, ash, azalea, oak, sycamore, dogwood.
• Greenhouse/potted: Cyclamen, ficus, lupine, palms, succulents, yuccas.
• Vegetables: Tomato, pepper, bean, cucurbits.

Diagnosis

• Small, dark, sunken lesions on leaves/veins (often along midrib).
• Underside: tiny tan-brown dots (pinhead-sized) = fruiting bodies (acervuli).
• Stems/twigs: cankers, dieback.
• Fruit: sunken, rotted spots with concentric rings.

Management

1. Sanitation (Foundation)

• Rake/destroy all fallen leaves, twigs, fruit—removes overwintering inoculum.
• Prune dead/diseased wood; sanitize tools.

2. Cultural Health

• Proper light, water, fertilizer—stress invites anthracnose.
• Avoid overhead irrigation; water early morning if necessary.
• Space for airflow.

3. Chemical (Rarely Needed)

• Newly transplanted or repeatedly defoliated plants may warrant preventive fungicide (chlorothalonil, copper, mancozeb, thiophanate-methyl).
• Apply at bud break; repeat per label in wet springs.

Key Insight

Anthracnose is a disease of wet springs and neglected sanitation. The gardener who rakes every leaf in fall, prunes cleanly in winter, and waters at the base rarely sees severe anthracnose. The one who leaves the debris creates next year's epidemic.