Plant disease - Knowledgebase Question

Salinas, CA
Question by nbennett7
August 14, 2007
I have a young crepe myrtle tree that I planted several months ago. It has been doing well, but recently I noticed an odd white spotting on some of the leaves. When I rub the spots, they appear to be some sort of powdery substance. What is it and how can I treat it?

Answer from NGA
August 14, 2007


It sounds like your tree may have powdery mildew. You may want to prune to remove the infected leaves, and to open the canopy up to better air circulation. You must also rake up and remove any fallen foliage as that will spread the disease. Here is a good home remedy: Make a baking soda solution and spray it onto the affected plants. To make this solution mix 1 tablespoon of baking soda and 2 1/2 tablespoons of ultra-fine horticultural oil with a gallon of water. The oil is slightly fungicidal and acts to help the baking soda coat the leaf and hang on longer. Apply as a spray as soon as the mildew appears and every 10-14 days thereafter. Be sure to coat all surfaces!

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