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Powdery mildew affecting Coast crape myrtles
The Coast Gardener Newspaper and Web Column - June 30, 2001

I have seen several crape myrtles suffering from powdery mildew along the Coast. It is not uncommon to see this disease at this time of the year. Since the crape myrtles are actively blooming right now, this problem is quite noticeable.

In extreme cases, entire twigs may be blighted by the powdery mildew fungus. While this fungus disease will not kill affected crape myrtles, blighted foliage detracts from the appearance of the popular Southern landscape plant.

Leaves infected early in the season by the powdery mildew fungus become curled and distorted. Infected younger leaves have blister-like areas that quickly become covered with the mildew. On older leaves, large white patches of fungus growth appear, but there is little leaf distortion. Flowers that originate from infected buds often become blighted as well.

Powdery mildew has been more common this season because of dry weather, warm days and occasional cool nights. These conditions favor the development of this disease. If powdery mildew is showing up in your landscape, what can you do about it? If infection is not excessive, twigs may simply be removed by pruning. Twigs and branches that are severely affected will likely require fungicide treatment for full recovery.

Homeowners who have had severe crape myrtle powdery mildew problems in past seasons should start fungicide applications immediately after the first sign of the disease. It may be necessary to continue fungicide sprays until leaves are mature, at which time they are less susceptible to the powdery mildew fungus. Fungicide applications can be made during the flowering period to prevent blossom blight infection, too.

Several fungicides containing the active ingredient propiconazole help reduce crape myrtle powdery mildew. It is important to read label directions carefully for application rates. Several fungicides may also be used for the control of powdery mildew and other diseases on roses, dogwoods, and other ornamental plants. Always consult the label for specific information.

Homeowners who plan to use crape myrtles as specimen plants should consider using those that are resistant to powdery mildew. Resistant cultivars are now available in nurseries and garden centers. Some of the pink cultivars include Sioux, Biloxi, Comanche, Hopi, Miami, Osage, Pecos, Tuscarora and Tuskegee. White cultivars include Acoma and Natchez. Lavender cultivars available are Apalachee, Lipan, Muskogee, Wichita, Yuma and Zuni. A red cultivar that is resistant is called Tonto.

Crape myrtles can add a burst of color in your summer landscape. Don't let powdery mildew stop you from enjoying their showy array of blooms this year. If you are thinking about planting crape myrtles, don't forget to ask for resistant varieties at your favorite nursery or garden center.

These archived gardening columns were written by Chance McDavid, former Harrison County Extension Agent.