Apply all chemicals according to the directions indicated on the label.Ĭercospora Leaf Spot: Leaf spots caused by Cercospora lythracearum may appear on crape myrtles and are caused by the fungus Cercospora species. If the disease is severe enough to warrant chemical control, select a fungicide containing one of the following: myclobutanil, propiconazole, thiophanate-methyl, or copper-based fungicides (see Table 1 for specific products). Varieties to Avoid: ‘Gray’s Red,’ ‘Orbin’s Adkins, ‘ ‘Carolina Beauty,’ ‘Wonderful White,’ ‘Raspberry Sundae’, and ‘Potomac.’ ‘Catawba,’ ‘Cherokee,’ ‘Seminole’, and ‘Yuma’ have some resistance to powdery mildew.Varieties with very good resistance to powdery mildew and fairly good tolerance to Cercospora leaf spot include: ‘Apalachee,’ ‘Basham’s Party Pink,’ ‘Caddo,’ ‘Dodd #2’, ‘Fantasy,’ ‘Glendora White,’ ‘Hopi,’ ‘Lipan,’ ‘Miami,’ ‘Osage,’ ‘Pecos,’ ‘Regal Red,’ ‘Sarah’s Favorite,’ ‘Sioux,’ ‘Tonto,’ ‘Tuscarora,’ ‘Tuskegee,’ ‘Velma’s Royal Delight’, and ‘Wichita.’ ‘Apalachee’ and ‘Fantasy’ are totally resistant to powdery mildew.The Lagerstroemia indica x fauriei hybrids developed at the U.Plant Resistant Varieties: The extent of resistance to powdery mildew for a particular variety may vary from location to location and may depend on particular conditions occurring in the environment. Once these sprouts become infected, the fungus easily spreads to the upper portions of the plant. Remove sprouts (suckers) at the base of the plant as they occur since they are very susceptible to powdery mildew. Removing diseased twigs and branches may be possible if only a few shoots are infected. Susceptible varieties of crape myrtle should be avoided.
Prevention & Treatment:The most effective control measures include locating plants in full sun, removing sprouts from the base of the plant, and planting resistant varieties. Development of the fungus is favored by high humidity at night and dry, mild daytime conditions, as often occur during the spring and fall. The disease is most serious in shady, damp locations, especially where plants are crowded and air circulation is poor. Infected parts of the plant become distorted and stunted. Heavily infected flowers may fail to open.
Patches of white to grayish powdery growth occur on the surfaces of leaves, flowers, and new shoots. Powdery Mildew: Powdery mildew is one of the most common problems of crape myrtle, and it is caused by the fungus Erysiphe lagerstroemiae. James Blake, ©2007 HGIC, Clemson Extension Powdery mildew typically coats the flower buds (above) and foliage of crape myrtle.