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Prevention & Treatment: In most cases, this disease doesn’t result in significant damage, but severe and repeat infections each year can significantly weaken a tree. If spotting does not appear on the bracts, the disease may not be severe on the leaves. When dry weather follows bud swell and bloom, the symptoms are rarely seen on the flower bracts. This fungus survives from year to year on infected twigs, fruits, and other tissues.įrequent rains or extended periods of high humidity are needed for disease development.

As further infections occur, individual spots eventually merge to form larger spots. When the infection is severe, these spots can cause flower bracts and leaves to become wrinkled and distorted. Symptoms are small (⅛ inch), tan spots with reddish-purple borders. The flower bracts are usually attacked first, then the leaves, young shoots, and fruit of dogwoods, primarily during wet spring weather. Spot Anthracnose: This disease is caused by the fungus Elsinoe corni, one of the most common leaf diseases of flowering dogwoods. Joey Williamson, ©2009 HGIC, Clemson Extension Spot anthracnose on dogwood ( Cornus florida) petals. It is recommended to alternate fungicides to decrease the chance of fungi developing resistance. The first four fungicides listed have foliar systemic properties and may need to be sprayed less often than sulfur or copper fungicides. Product labels will provide information on how often to spray. Some control can also be obtained with triadimefon, thiophanate methyl, sulfur, or copper fungicides (see Table 1 for specific products). Very effective fungicides for dogwood powdery mildew control include myclobutanil and propiconazole.

For fungicides to be effective, they must be applied as soon as symptoms are noticed. If the 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.

sericea) is very susceptible to powdery mildew. ‘Cherokee Brave’, ‘Springtime’, and ‘Pygmy’ have partial resistance. The flowering dogwood ( Cornus florida) cultivars ‘Appalachian Joy’, ‘Appalachian Blush ‘, ‘Appalachian Snow’, and ‘Appalachian Mist’ are very resistant to powdery mildew. Cultivars of the oriental dogwood Cornus kousa (such as ‘Milky Way’, ‘Milky Way Select’, and ‘National’) and many of the Cornus florida x Cornus kousa hybrids (such as ‘Aurora’, ‘Constellation’, ‘Celestial’, and ‘Stellar Pink’) are generally resistant to powdery mildew. Resistant species and cultivars are available and should be considered for new plantings. Improve air circulation and sunlight penetration around the tree by removing overhanging branches and crowding vegetation. Prune out dead and infected branches and twigs. Begin by raking up and destroying all fallen leaves. Infection that begins early in the season can be devastating and may warrant the use of fungicides.Ĭultural controls should be the first line of defense. Prevention & Treatment: Most powdery mildews of landscape trees occur late in the summer and are therefore of little consequence. Warm, dry days and cool, damp nights favor disease development. Powdery mildew is most common in dense, shady areas where the air circulation is poor. Spores are spread by wind to surrounding dogwood plants. Infected leaves exhibit marginal leaf scorch, dead patches, reddish discoloration, yellowing, and premature defoliation. New growth is covered with a fine, white, powdery coating, typically on the upper leaf surface. Powdery Mildew: Erysiphe pulchra (formerly Microsphaera pulchra) is the fungus that attacks leaf surfaces and tender shoots and causes powdery mildew. James Blake, ©2007 HGIC, Clemson Extension Powdery mildew on dogwood (C ornus florida) leaves.