Flowering Dogwood Anthracnose and Leaf Spots: Causes and How to Fix It
Spots, blotches, and twig dieback on a flowering dogwood usually point to a fungal disease — most seriously dogwood anthracnose, but also common leaf-spot fungi that look alarming yet are largely cosmetic. Telling them apart matters, because anthracnose can be fatal to a stressed tree while ordinary leaf spot rarely is. Here's how to identify the cause and respond.
Dogwood anthracnose (the serious one)
What's happening
A destructive fungal disease (Discula destructiva) that begins as tan leaf spots with purple borders, then spreads into larger blotches, killing leaves and moving down the twigs into branches. It can girdle limbs, trigger water-sprout growth on the trunk, and over several years kill a tree — especially one already stressed by drought or deep shade.
How to confirm
Look for tan blotches rimmed in purple, leaves that brown and cling to the tree rather than dropping, dying twigs from the lower canopy upward, and sprouts along the trunk and main limbs. It's most aggressive in cool, wet springs and in shaded, humid sites.
How to fix it
Prune out dead and dying wood well below the infection, disinfecting tools between cuts, and remove fallen leaves and twigs from the ground. Improve light and airflow, keep the tree well-watered and mulched to reduce stress, and apply a labeled fungicide on a protective schedule starting at budbreak in severe cases. Trees in advanced decline are often best replaced with a resistant cultivar.
Prevent it
Plant in morning sun with good air movement, avoid wounding the bark, keep the tree unstressed with steady moisture, and choose anthracnose-resistant varieties.
Spot anthracnose and ordinary leaf spots (mostly cosmetic)
What's happening
Several less-serious fungi cause small, scattered spots — spot anthracnose (Elsinoë) makes tiny reddish-purple flecks on bracts and leaves, while Septoria and Cercospora leaf spots produce small angular brown or purple-bordered spots. These disfigure foliage and flowers but rarely threaten the tree's life.
How to confirm
Spots are small, numerous, and scattered rather than large spreading blotches; twigs and branches stay alive; and bracts may be pocked in wet springs. The tree leafs out and grows normally otherwise.
How to fix it
Usually no treatment is needed — rake and dispose of fallen leaves to reduce spores, and the tree carries on. For heavy, repeated infection on a prized specimen, a labeled fungicide applied as leaves emerge will reduce spotting.
Prevent it
Clean up leaf litter each fall and keep foliage dry by watering at the roots rather than overhead.
Wet, cool, poorly ventilated conditions
What's happening
All of these fungi thrive on persistently wet foliage and stagnant, humid air. Overhead watering, crowding, deep shade, and rainy spring weather keep leaves wet long enough for spores to infect.
How to confirm
Disease is worst after a cool, wet spring or in a shaded, crowded, poorly drained spot, and the foliage routinely stays damp into the day.
How to fix it
Thin the canopy lightly (after bloom) and clear crowding plants to boost airflow, switch to root-zone watering, and improve drainage on soggy sites. Drier, better-ventilated foliage dramatically slows every one of these fungi.
Prevent it
Water at the base early in the day, space and thin for airflow, and avoid planting in damp, sunless pockets.
Drought and overall tree stress
What's happening
A dogwood weakened by dry soil, scorching sun, or root damage has fewer defenses, and fungal diseases — anthracnose especially — hit stressed trees hardest and progress fastest.
How to confirm
The tree has been through drought, heat, or transplant shock, leaves scorch at the edges, and disease symptoms are noticeably worse than on a well-watered neighbor.
How to fix it
Relieve the stress first: water deeply during dry spells, refresh a cooling ring of mulch off the trunk, and provide afternoon shade if the site is too hot. A vigorous tree shrugs off mild infection that would overwhelm a struggling one.
Prevent it
Keep the tree consistently watered and mulched, and site it in the dappled, sheltered conditions it prefers.
When to worry (and when not to)
Scattered small leaf spots on a tree that is otherwise leafing out and growing well are cosmetic — clean up fallen leaves and don't worry. Act quickly when you see the hallmarks of true anthracnose: purple-bordered blotches, leaves that brown and stay attached, twig dieback creeping up from the lower canopy, and sprouts erupting on the trunk. That pattern, especially after a cool wet spring, calls for prompt pruning, sanitation, and stress relief — and on a declining tree, replacement with a resistant cultivar before the disease spreads.