Plant Disease Management Handbook

Cause Erysiphe pulchra (formerly Microsphaera penicillata) and Phyllactinia guttata can produce white mycelial growth on leaves, buds, flowers, and new stems of dogwood. Powdery mildew on dogwood has been an increasing problem in Southeastern States since 1995, was reported from Washington during 1999 and found in Oregon in 2002.

A white, very thin, dry growth (mycelium) develops on the leaves.

Jay W. Pscheidt, 2020.

Leaf surfaces can be completely covered with the thin mycelia of powdery mildew.

Jay W. Pscheidt, 2020.

The underside of leaves can be covered with powdery mildew as well.

Jay W. Pscheidt, 2020.

Many Cornus spp can be infected by powdery mildew.

Jay W. Pscheidt, 2020.

Image related to Dogwood (Cornus spp.)-Powdery Mildew
Note the white, powdery appearance of the new leaves.
Photo by Robin Rosetta, 2006.

Cause Leaf spots may be caused by a wide variety of fungi including Cercospora, Elsinoe corni (cause of spot anthracnose), Phyllosticta, Ramularia, Septoria, Sphaceloma, Phlyctema vagabunda and others.

Septoria seems to a problem on these variegated types.

OSU Plant Clinic Image, 2016.  

Minor leaf and bract spotting fungus, Phlyctema vagabunda.

Neil Bell, 2017.

Image related to Dogwood (Cornus spp.)-Leaf Spots
Leaf spots on this Cornus sp. were due to Septoria sp.
Photo by Jay W. Pscheidt, 1992.
Image related to Dogwood (Cornus spp.)-Leaf Spots
Numerous spots due to Septoria.
Melodie Putnam, 2007.

See:

Maple (Acer spp.) - Leaf Scorch

Dogwood (Cornus spp.) - Anthracnose

Image related to Dogwood (Cornus spp.)-Leaf Scorch
Margins and tips of dogwood leaves often turn brown and die during the summer and fall. Leaf margins may also tend to fold upward.
Photo by Ralph S. Byther
Image related to Dogwood (Cornus spp.)-Leaf Scorch
Robin Rosetta, 2007.
Several dogwood leaves

Light brown or tan leaf margins tend to indicate rapid water loss during high heat events. This tree was recently transplanted.

Jay W. Pscheidt, 2019.

See:

Dogwood (Cornus spp.) - Root Rot

Image related to Dogwood (Cornus spp.)-Collar Rot

Cankers from this pathogen can be seen above the soil line and may appear sunken.

OSU Extension Plant Pathology Slide Collection.

Cause Various fungi such as Phoma, Phomopsis, and Cytospora. Neonectria ditissima (formerly Nectria galligena) is a problem on native dogwood. Usually these fungi are opportunistic and are able to attack only trees weakened by drought, cold, root problems, or wounds and mechanical injury.

Image related to Dogwood (Cornus spp.)-Branch Cankers

Cornus alternifolia 'Golden Shadows' with twig cankers caused by Phoma.

OSU Plant Clinic Image, 2013.

See:

Rose (Rosa spp.) and hybrids - Armillaria Root Rot

Wood decay in this sample was due to Armillaria.

OSU Plant Clinic Image, 2017.

See:

Dogwood (Cornus spp.) - Leaf Spots

Image related to Dogwood (Cornus spp.)-Anthracnose
All the reddish spots on these flower bracts are due to anthracnose.
Photo by Ralph S. Byther

Many leaf lesions can disfigure leaves and stunt growth when disease pressure is high.

Jay W. Pscheidt, 2010.

2 dogwood leaves

Leaf blight due to anthracnose on this Cornus kousa.

OSU Plant Clinic Image, 2010.

Image related to Dogwood (Cornus spp.)-Anthracnose
Notice the twig dieback from this fungal disease. Note the dead leaves.
Photo by Everett Hansen, 1999.

Cause Sclerotinia sclerotiorum is a fungus that overwinters as small black structures (sclerotia) attached to decomposing infected plant portions. Sclerotia may survive more than several years. After a moisture-conditioning period of at least 70 days, they produce a small, stalked, cup-shaped fruiting structure (apothecium), which releases spores into the air. Spores may infect blossoms and senescing leaves. After colonizing, the fungus can invade healthy parts of the plant.

Cause The soilborne fungi or fungus-like microorganisms, Fusarium spp., Pythium spp., and Rhizoctonia solani, may attack before, during, and after germination. In the Pacific Northwest, Pythium spp. are the major cause of pre- and post-emergence damping-off of young dill seedlings. Pythium is favored by cool, wet soils.

Cause Alternaria species. These fungi survive in residues of affected crops including carrot, parsley, celery, and parsnip; they also may be seedborne. Spores move by wind and water.

Symptoms Seedlings and older leaves are more susceptible. Yellow spots develop and centers may be coated with sooty black spore masses.

Cultural control