Plant Disease Management Handbook

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Note Common name is used for many plants (at least 5 genera) with silvery or whitish foliage.

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Photo part of OSU Extension Plant Pathology Slide

Cause Many fungi and bacteria cause a leaf spot on Dracaena spp., but Phoma draconis (formerly Phyllosticta draconis) is most common. Peperomia also is susceptible. Wet, humid conditions favor disease development. Yellow spots can also be from magnesium deficiency.

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Fir, Douglas (Pseudotsuga menziesii)

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Dogwood (Cornus spp.) - Collar Rot

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These rotted roots were due to a Phytophthora sp.

OSU Plant Clinic Image, 2014.

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.

Numerous spots due to Septoria.

Melodie Putnam, 2007.

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Maple (Acer spp.) - Leaf Scorch

Dogwood (Cornus spp.) - Anthracnose

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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

Robin Rosetta, 2007.

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.

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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.