Incomplete bloom on crape myrtle

Asked May 2, 2020, 7:06 PM EDT

What can I use to control mildew on my crape myrtle? I have several varieties unfortunately I do not know what variety they are. One is a tall dark red that looks healthy early on but the bloom clusters do not completely bloom out. I know I have mildew on some of them but the red one has spots on the leaves which turn yellow and drop when it is starting to bloom and drops all of its leaves by late summer. The plant is 15 years old and 15 to 20 feet tall with the problem worsening each year. Is there a spray to control this problem as well as the mildew I know I have?

Howard County Maryland

1 Response

Here is our page on powdery mildew: https://extension.umd.edu/hgic/topics/powdery-mildew-trees-and-shrubs Is is possible that your crape myrtles are now in more shade than they were previously? Can you increase light? Also air circulation? Thin them?

There are many new varieties of crape myrtle that are resistant. You may want to replace with one. Be sure it is resistant specifically to powdery mildew.

The leaf spots are cercospora, a fungal leaf spot. Be sure to only water at the base, not overhead. Increase light and air circulation. If you apply a fungicide, start when leaves begin to appear in spring. We have had a lot of wet months the past two years. If you had no problems before that, it's possible that some dry years may improve the appearance. Rake up and dispose of infected leaves in the trash.

Ellen