Dogwoods are lovely but sensitive trees. They are understory trees by nature, used to cool, moist, acidic forest soil in dappled shade. When they decline, it is usually a combination of stress and a pest or disease that took advantage of it. Finding both parts is the key to saving the tree.

Table of Contents

The short answer: the most common reasons a dogwood dies back are dogwood anthracnose (leaf spots with purple borders, then twig and branch dieback from the bottom of the tree up), dogwood borer (holes, sawdust and loose bark on the lower trunk, often after mower damage), and stress from drought, full sun or poorly drained soil. Powdery mildew weakens trees but rarely kills them. Small dogwoods with borers can die within one to two seasons.

Match the symptoms

What you see	Likely cause	How serious
Tan leaf spots with purple borders in late spring, blighted leaves hanging on, dieback starting low in the crown	Dogwood anthracnose	Serious
Holes in the bark, loose bark, sawdust-like frass, rough knotty areas on the trunk	Dogwood borer	Serious, especially on young trees
White powdery coating on leaves, scorched edges, early leaf drop	Powdery mildew	Moderate
Small spots on bracts and leaves in wet spring	Spot anthracnose	Minor
Brown, scorched leaf edges in summer	Drought or too much sun	Moderate
Pale, yellow-green leaves	High soil pH (chlorosis)	Moderate, slowly worsening
Decline after construction or heavy mulch against the trunk	Root and trunk stress	Serious

Dogwood anthracnose

The University of Maryland Extension describes dogwood anthracnose (caused by Discula destructiva) as once the most serious disease of dogwoods, now less common but still capable of killing trees. Early symptoms appear in mid to late May as leaf spots with tan or purple borders. In wet weather the spots enlarge and kill whole leaves, which hang on the branches. The disease moves into twigs and branches, causing dark cankers and dieback. If it reaches the main trunk, the tree can die.

What to do, according to UMD:

Prune out all dead and dying twigs and limbs in dry weather.
Remove water sprouts and suckers, which are especially susceptible.
Rake up fallen leaves in fall and remove dead leaves hanging on the tree.
Avoid over-fertilizing.
Plant resistant cultivars when replacing. Kousa dogwood and many kousa hybrids are more resistant.

Dogwood borer

Clemson Extension describes the dogwood borer as the larva of a wasp-like clearwing moth that feeds beneath the bark. Borers can become established only where they find a wound or opening in the bark. Signs include:

Leaves that turn red and drop early.
Bark sloughing off around holes in the trunk or branches.
Brown, sawdust-like frass near holes in late summer.
Rough, knotty areas on the trunk and large branches.

Clemson warns that infested young trees can be killed in one to two seasons. The best prevention is to avoid bark wounds: keep lawn mowers and string trimmers away with a wide ring of mulch.

Powdery mildew

The University of Maryland now considers powdery mildew the most serious disease of dogwood. It causes a white coating on leaves, marginal scorch, reddish discoloration and early leaf drop. It weakens the tree over time, especially combined with drought. Clemson suggests raking fallen leaves, pruning out infected twigs and improving air flow. Resistant cultivars are available.

Stress: the common thread

The Morton Arboretum notes that poorly drained soils, wind, salt and drought stress predispose flowering dogwood to insect and disease problems. The University of Maryland lists conditions dogwoods do not tolerate: full sun, hot and dry conditions, air pollution, poorly drained sites and saturated soil.

Other common stress factors:

Shallow roots. Dogwoods compete poorly with lawn grass and need water during dry summers.
Planting too deep or mulch against the trunk. Both can lead to trunk decay.
High pH. The Morton Arboretum notes flowering dogwood prefers acid soil and gets pale green leaves in high pH soils.

Can it be saved?

Situation	Outlook
Leaf spots, some twig dieback, mostly healthy crown	Good with sanitation pruning and better care
Several dead branches, borer holes on one side	Fair; prune, protect the trunk, water well
Dieback reaching the trunk, or extensive borer damage	Poor; plan for replacement
More than half the crown dead	Removal is usually best

Care that helps any declining dogwood

Water deeply during dry spells. UMD suggests checking soil moisture 4 to 6 inches deep.
Keep mulch to about 3 inches, pulled back from the trunk.
Remove grass from the root zone.
Fertilize only based on a soil test.
Prune dead wood in dry weather.

When to call a certified arborist

If the trunk has cankers or borer holes, or if dieback is spreading year after year, have a certified arborist or your county extension office confirm the cause. The ISA Find an Arborist directory can help.

If your dogwood looks healthy but won’t flower, read why a dogwood isn’t blooming. For safe pruning, see how and when to prune a dogwood.

Sources

Dogwood Diseases and Insect Pests, Clemson Cooperative Extension HGIC
Dogwood Anthracnose, University of Maryland Extension
Growing Flowering Dogwood Trees, University of Maryland Extension
Flowering Dogwood, The Morton Arboretum

Top photo: NatureServe, CC BY 2.0, via Wikimedia Commons

Why Is My Dogwood Tree Dying?