Dogwood trees are much loved for their spring blooms, but they can face several fungal, insect, and stress-related problems. Common issues include dogwood anthracnose, powdery mildew, various leaf spots, branch cankers, root rot/collar rot, and borers.
Symptoms range from white powder on leaves to tan spots, wilted branches, or bark lesions. Early diagnosis is key: for example, powdery mildew shows a white coating (upper leaf surface) in summer, whereas dogwood anthracnose causes tan-purple leaf spots and dieback in cool, wet spring conditions.
Dogwood diseases and disorders
A healthy dogwood resists disease better. Nonetheless, several pathogens and pests can cause visible symptoms. Below is an overview of major dogwood disorders and how to recognize and manage them.
1. Dogwood Anthracnose
- Cause: Fungus Discula destructiva.
- Symptoms: Tan or reddish spots on leaves and flower bracts; leaf edges scorched or blighted; gray dead leaves often cling to tips. Infection spreads to twigs and branches, causing sunken cankers and dieback (Figure: sunken brown cankers on limbs). Fall/winter may show cankered twigs.
- Prevention: Plant resistant dogwood varieties (e.g. Cornus kousa cultivars) and site trees in sunlight with good air flow. Remove and destroy fallen leaves and dead twigs each fall. Mulch to conserve moisture and avoid wounding the trunk. Keep trees healthy by watering in droughts and avoiding excess nitrogen fertilizer.
- Treatment: Prune out and destroy infected branches during dry weather. Fungicide sprays (e.g. chlorothalonil or propiconazole) can protect new leaves if applied at bud break and repeated through spring. Once cankers girdle a trunk or major branch, removal of that limb or tree is usually necessary.
A serious fungal disease (Discula destructiva) that often begins as leaf spots and can progress into stem cankers. Dogswood anthracnose was introduced to North America in the 1970s. It most severely affects native Cornus florida and Pacific dogwood (C. nuttallii); Cornus kousa and hybrids are more resistant
2. Powdery Mildew
- Cause: Powdery mildew fungi (e.g. Erysiphe species).
- Symptoms: Fine white powder on upper leaf surfaces; new leaves may curl or twist. Infected leaves often develop marginal brown scorch, dead spots, and yellowing, leading to early leaf drop. Usually worse on lower or inner canopy leaves.
- Prevention: Promote air circulation by pruning to open the canopy. Avoid overhead watering and crowding plants. Rake and destroy fallen leaves in autumn to remove overwintering spores. Plant resistant dogwood cultivars (some Cornus kousa hybrids) if powdery mildew is chronic.
- Treatment: In many landscapes it’s cosmetic once midsummer arrives. For severe cases early in the season, fungicide sprays (e.g. myclobutanil, propiconazole) can help. Otherwise, focus on cultural controls (leaf removal, pruning, mulching) which are effective and recommended as first line.
A common fungal infection causing a white, powdery coating on leaves. Powdery mildew (caused by Erysiphe pulchra and related fungi) often appears in late spring to summer. It thrives in humid, shaded conditions.
3. Leaf Spot Diseases (Spot Anthracnose, Septoria, Cercospora)
- Cause: Primarily Elsinoë corni (spot anthracnose), Septoria cornicola, Cercospora spp., etc.
- Symptoms: Small (1/8–¼”) tan to purplish spots on leaves and flower bracts. Elsinoë spots have purple borders and may distort bracts and young leaves. Septoria/Cercospora spots (summer) are angular tan/brown spots with dark margins. Heavy infestations can cause leaves to wrinkle or drop prematurely, but minor spotting is usually cosmetic.
- Prevention: Remove leaf litter and prune lightly to improve airflow. Since these spots need moisture, avoid overhead irrigation in wet springs. Resistant varieties (e.g. some kousa hybrids) can reduce incidence.
- Treatment: Usually unnecessary except for severe recurring outbreaks. If needed, apply fungicides (the same ones used for anthracnose or powdery mildew) starting at budbreak and repeat 2–4 times in wet springs. For mild cases, collecting and disposing of infected leaves each fall and maintaining tree vigor is sufficient.
Several foliar fungi cause spots on dogwood leaves and bracts. These are often most active in spring or summer rains. The two most common leaf spots are spot anthracnose (Elsinoë corni) and Septoria/Cercospora spots.
4. Twig and Branch Cankers
- Cause: Fungi such as Botryosphaeria sp. and Diplodia sp. infect through wounds.
- Symptoms: Sunken, discolored patches or cracks on twigs/branches. May girdle small limbs, causing dieback above the canker. Often first seen as a brown or black oval on the bark that enlarges over months.
- Prevention: Keep trees healthy to resist infection (water in drought, avoid nutrient excess). Do not allow branches to stay wet for long periods. Minimize wounds from pruning or animals.
- Treatment: Prune out infected twigs/branches several inches below the canker as soon as they are found, and burn or dispose of them. No practical chemical cure exists once cankers form, so sanitation is key.
Sunken lesions on small branches or twigs, often caused by opportunistic fungi. Canker diseases usually show up after repeated stress or minor injury. The most common culprits are Botryosphaeria and Diplodia fungi.
5. Borers (Dogwood Borer & Twig Borer)
- Cause: Insect larvae (borers) tunneling in cambium.
- Symptoms: Small wet-looking patches or holes on the bark; sawdust-like frass accumulating at injury sites. Early signs include wilting and reddening of leaves on affected branches. Infestations can kill young trees or twist/dieback older limbs. Over time, infested trees develop rough, knotty bark from callus tissue.
- Prevention: Protect bark from injury (lawn equipment, storms). Keep trees vigorous: mulch, water in dry spells, and fertilize based on soil tests. Inspect trees in late spring and summer for exit holes or frass.
- Treatment: Prune and destroy heavily infested branches. For dogwood borer, timed insecticide sprays (e.g. permethrin) on the trunk and major branches from late April through mid-summer can reduce populations. Repeat as label directs. There are no targeted pesticides for twig borers, so manual removal of infested twigs is the usual control.
Insect larvae that tunnel under bark, interrupting water transport. The dogwood borer (Synanthedon scitula) is the most damaging. A clearwing moth larva, it typically attacks stressed or wounded trees. Another common pest is the dogwood twig borer (Oberea tripunctata), which girdles small branches.
6. Root/Collar Rot (Phytophthora)
- Cause: Phytophthora water molds entering through wounds at the root collar.
- Symptoms: Stunted growth; individual branches or one side of the tree may wilt, turn bronze/red early, then drop leaves. A sunken, cracked canker forms around the trunk base. In advanced cases, large sections of bark peel and brown, and the entire tree can die rapidly.
- Prevention: Avoid planting dogwoods in wet soils or low spots. Ensure good drainage and don’t bury the root collar in mulch or soil. Sterilize tools after pruning other Phytophthora-prone trees.
- Treatment: There is no cure once symptoms appear. Remove and destroy infected trees. Do not replant dogwoods in the same spot for several years. Some systemic fungicides may protect healthy trees if used preventatively, but by the time cankers show, the infection is usually fatal.
A soil-borne water mold causing root and crown decay. Phytophthora species (notably P. cactorum and P. cinnamomi) infect dogwoods at the base or roots, especially after flooding or in poorly drained soils.
7. Verticillium Wilt (Rare)
- Cause: Verticillium spp. fungi in soil.
- Symptoms: On susceptible hosts, wilting, leaf yellowing, branch dieback, and dark streaking in the sapwood occur. In dogwoods this disease is uncommon, but if present it typically manifests as wilting or branch decline on one side of the tree.
- Prevention: Since dogwoods are usually not a preferred host, this disease is extremely uncommon. Avoid planting dogwoods in the footprints of previously infected oaks, maples, or other Verticillium-prone trees.
- Treatment: No effective fungicide cures Verticillium. If diagnosed, prune out and destroy affected limbs and improve overall vigor with deep watering and fertilization. (Because dogswood are resistant, this is rarely needed.)
A soil-borne fungus that blocks water-conducting vessels. Although Verticillium wilt affects many ornamentals, dogwoods are generally resistant to it. However, it is worth mentioning for completeness.
8. Environmental Stress (Drought and Leaf Scorch)
- Cause: Dry soil conditions, excessive sun exposure, or root damage.
- Symptoms: Browning and crisping of leaf edges or between veins (leaf scorch). In extreme stress, entire leaves wilt and turn brown. Young or newly planted dogwoods often show stress quickly in sunny lawns.
- Prevention: Plant dogwoods in partial shade (morning sun, afternoon shade). Apply 3–4 inches of mulch around the root zone to retain moisture (kept a few inches away from the trunk). Water deeply during dry spells, especially for the first few years after planting.
- Treatment: No chemical fix is needed – simply water as needed. In severe cases, move or replace the tree in a better site. Ameliorate soil compaction and avoid lawn mower injuries. Over time, trees often recover if drought stress is relieved.
Non-pathogenic problems that mimic disease. Dogwoods have shallow roots and can suffer in full sun or drought. They may show leaf scorch or other stress symptoms during hot, dry weather.
Diagnosis Tips
White powder vs. spots: If leaves have a white, powdery coating on top, it’s powdery mildew. If you see brown or tan blotches (often with purple edges) primarily after spring rains, suspect anthracnose or leaf spot.
Pattern and timing: Spot anthracnose (Elsinoë) typically shows tiny spots on flowers/bracts in spring, whereas Septoria/Cercospora spots build up slowly in summer. Dogwood anthracnose often starts low in the tree and moves upward during a cool, wet spring.
Scorch vs. disease: Dry, crispy leaf edges on a sunny day usually mean drought stress (leaf scorch). If similar browning is accompanied by yellowing veins or occurs after watering, consider root/collar rot.
Borers vs. disease: Vertical strips of missing bark or holes with sawdust (frass) indicate borers, not fungi. Red leaves on only one branch or wet spots on bark may also signal borer activity, while fungal diseases rarely cause frass.
Branch dieback: Sudden dieback in midsummer suggests borer or canker; slow decline over years hints at cumulative stresses (drought, site issues).
Seasonal Timing
Spring (bud break to early summer): Watch for dogwood anthracnose and spot anthracnose, which cause leaf spots and blighting in cool, wet springs. Petal blight (Botrytis) may attack blooms if very wet.
Summer (midsummer): Powdery mildew often peaks in warm, humid weather. Also look for leaf spots like Septoria in summer rains. Dogwood borer adults emerge in late spring/early summer, and their damage becomes visible by late summer.
Fall: Remove leaves to prevent leaf spots and anthracnose from overwintering. Collar rot symptoms (discolored foliage, cankers at base) may become obvious. Late summer watering helps prevent winter scorch.
Winter: Inspect for cankers or sunken areas on twigs during dormancy. Prune any diseased wood before spring growth.
Dogwood Tree Problems
Dogwood trees are susceptible to a range of diseases, pests, and environmental stresses, but most problems can be managed successfully when identified early. Fungal diseases such as anthracnose, powdery mildew, and leaf spots are among the most common issues, while borers, cankers, and root rot can cause more serious long-term damage. Regular inspection, proper watering, good airflow, and seasonal cleanup of fallen leaves are the best ways to keep dogwoods healthy and resilient.
If you’re diagnosing problems on other landscape trees, you may also find our guides to common oak tree diseases and common maple tree diseases helpful. Many symptoms—such as leaf spots, cankers, dieback, and wilt—can appear across different tree species, making it useful to compare conditions and treatment options when troubleshooting tree health issues.
