Powdery Mildew Of dogwood

Disease Information

Powdery Mildew

 Symptoms

Erysiphepulchra (formerly Microsphaerapulchra) is the fungus that attacks leaf surfaces and tender shoots and causes powdery mildew. New growth is covered with a fine, white, powdery coating, typically on the upper surfaces of the leaves. Infected leaves exhibit marginal leaf scorch, dead patches, reddish discoloration, yellowing and premature defoliation. Spores are spread by wind to surrounding dogwood plants.

COMMENTS on disease

Powdery mildew is most common in dense, shady areas where the air circulation is poor. Warm, dry days and cool, damp nights favor disease development.

Management

 Most powdery mildews of landscape trees occur late in the summer and are therefore of little consequence. Infection that begins early in the season can be devastating, and the use of fungicides may be warranted.

Cultural controls should be the first line of defense. Begin by raking up and destroying all fallen leaves. Prune out dead and infected branches and twigs. Improve air circulation and sunlight penetration around the tree by removing overhanging branches and crowding vegetation. Resistant species and cultivars are available and should be considered for new plantings. Cultivars of the oriental dogwood Cornuskousa (such as `Milky Way`, `Milky Way Select`, and `National`) and many of the Cornusflorida x Cornuskousa hybrids (such as `Aurora`, `Constellation`, `Celestial`, and `Stellar Pink`) are generally resistant to powdery mildew. The flowering dogwood (Cornusflorida) cultivars `Appalachian Joy`, `Appalachian Blush `, `Appalachian Snow` and `Appalachian Mist` are very resistant to powdery mildew. `Cherokee Brave`, `Springtime`, and `Pygmy` have partial resistance. All other flowering dogwoods (C. florida) are susceptible. Red-twig dogwood (C. sericea) is very susceptible to powdery mildew.

If disease is severe enough to warrant the use of fungicides, be sure that the dogwood is a valuable specimen and the spray equipment can provide good coverage. For fungicides to be effective, they must be applied as soon as symptoms are noticed. Very effective fungicides for dogwood powdery mildew control include myclobutanil and propiconazole. Some control can also be obtained with triadimefon, thiophanate methyl, sulfur, or copper fungicides .

 



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