Looks like a white powdery mildew spring

posted by Randy Lemmon - 

I'm getting lots of Facebook and email images from folks being hit with white powdery mildew, especially on crape myrtles. 

It's been several years since I've seen a rash of questions on this topic, but it appears the consistent rains and increasing humidity are ramping it up this spring. 

What is powdery mildew? It's a grayish-white powder appearing suddenly on the tips of crape myrtles. It also affects roses, annuals, perennials, vegetables and others. I've even seen it lately on Gerbera daisies. In extreme cases, entire twigs may be blighted by the fungus. While it won't kill crape myrtles, blighted foliage detracts from the appearance of this popular Southern landscape plant. 

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

Powdery mildew is most common in dry weather, with warm days and cool nights - definitely the spring we have enjoyed! 

If an infection isn't excessive, affected twigs may simply be pruned away. But heavily infected plants will probably require fungicide treatment for full recovery. 

Crapes that suffer the worst experience are those that have been over-pruned, or massacred in the winter, when in fact they SHOULD be left alone. Crape myrtles are trees, and no tree should be pruned to the same spot year after year! 

Homeowners who have had severe powdery mildew problems in past seasons should start fungicide application immediately with 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 fungus. Fungicide can also be applied during the flowering period to prevent blossom blight infection. 

Fungicides to wash it off

Consan Triple Action 20 (Consan 20 or just Consan)

Neem oil

Banner-based fungicides (Fertilome liquid systemic, Ortho banner-based)

Homemade baking soda spray (2 teaspoons of baking soda, 2 quarts of water, ½ teaspoon of dish soap or Murphy's Oil Soap) 

Fungicides to prevent it

Copper-based fungicides (Kocide, Liqui-Cop)

Mancozeb

Banner-based fungicides (Anything with PPZ) 

PHOTO: University of Florida
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