WSU Extension

Hortsense

Dogwood
 
Disease
Anthracnose 
Armillaria root rot 
Collar rot 
Leaf scorch and leaf roll 
Powdery mildew 
Insect
Brown soft scale 
Lecanium scale 
Oystershell scale 



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Caption: Powdery mildew on dogwood
Photo by: J. Chushcoff
  
Dogwood : Powdery mildew
(revision date: 1/22/2016)


Biology
Dogwood powdery mildew is caused by a fungus. It infects leaves, current-year twigs, blossoms, fruit, and buds. The first symptom is often yellow patchy areas on a leaf that become necrotic. White, thin, dry fungal growth may be seen on the lower leaf surface directly below the leaf spots. All plant parts can become covered with mycelia and spores. Infected new growth that is expanding may be distorted. Small, black, pepperlike fungal structures may be seen in the white fungal growth on leaves during late summer and early fall. The fungus overwinters on the leaves.
Management Options


Non-Chemical Management
  • Plant disease-resistant cultivars. Limited information indicates that 'Karen's Appalachian Blush' and 'Jean's Appalachian Snow' are disease-resistant, 'Cherokee Brave' and 'Sterling Silver' are moderately resistant, and many cultivars of Cornus kousa are tolerant. Many red-flowered cultivars of Cornus florida are susceptible.
  • Improve air circulation to reduce relative humidity and accelerate drying of foliage.
  • Space plants well and plant in more exposed areas. Avoid planting in heavily shaded areas.
  • Irrigate with microjet sprinklers or soaker hoses to avoid wetting foliage.
  • Prune out and destroy infected tissue as it appears early in the year. It can be damaging to remove too many leaves.
  • In the fall, rake up and destroy fallen leaves.
Select non-chemical management options as your first choice!

Chemical Management

If you choose to apply a fungicide, your application will work better if it is made before symptoms develop. Follow label instructions for application timing and intervals. Complete coverage is important. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bi-Carb Old-Fashioned Fungicide [Organic]
    Active ingredient: potassium bicarbonate  |  EPA reg no: 54705-10
  • ferti-lome Liquid Systemic Fungicide II R-T-Spray
    Active ingredient: propiconazole  |  EPA reg no: 53883-184-7401
  • Monterey Horticultural Oil [Organic]
    Active ingredient: mineral oil/pet distillate light  |  EPA reg no: 48813-1-54705
  • Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
    Active ingredient: myclobutanil  |  EPA reg no: 9688-123-8845
  • This list may not include all products registered for this use.
Images

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Caption: Powdery mildew on dogwood
Photo by: J. Chushcoff