Powdery Mildew on crape myrtle

Disease Information

Powdery Mildew

 Symptoms and damage

Powdery mildew is one of the most common problems of crape myrtle, and it is caused by the fungus Erysiphe lagerstroemia. Patches of white to grayish powdery growth occur on the surfaces of leaves, flowers and new shoots. Heavily infected flowers may fail to open. Infected parts of the plant are usually distorted and stunted. The disease is most serious in shady, damp locations, especially where plants are crowded and air circulation is poor. Development of the fungus is favored by high humidity at night and dry, mild daytime conditions, as often occurs during the spring and fall.


 The most effective control measures include locating plants in full sun, removing sprouts from the base of the plant and planting resistant varieties. Susceptible varieties of crape myrtle should be avoided. Removing diseased twigs and branches may be possible, if only a few shoots are infected. Remove sprouts (suckers) at the base of the plant as they occur, since they are very susceptible to powdery mildew. Once these sprouts become infected, the fungus easily spreads to the upper portions of the plant.

If disease is severe enough to warrant chemical control, select a fungicide containing one of the following: myclobutanil, propiconazole, thiophanate-methyl, or copper-


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