What’s Wrong With My Crepe Myrtle? 4 Common Problems

August 22, 2013 | By | Comments (108)
Crepe myrtle

Photo: Steve Bender

Crepe myrtles are for the most part trouble-free. That’s why lazy slobs like Grumpy like them so much. But certain problems do crop up in summer that make you want to pull out the magnifying glass and burn some ants. Here are some of the most common problems and what to do about them.

Problem #1 — Sooty Mold

Black mold

Yuck! Black mold on crepe myrtle. Photo: lsuagnenter.com.

Sooty mold is a fungus that covers the leaves and looks like you just sprayed your crepe myrtle with asphalt. (Note to reader: This is seldom a good idea.) The mold doesn’t feed on the foliage. Instead, it grows on sticky honeydew secreted by sucking insects like aphids, scales, and white flies that do feed on the leaves. Get rid of the bugs and black mold will go with them.

Solution: Spray your crepe myrtle according to label directions with insecticidal soap, horticultural oil, neem oil, or Natria Multi-Insect Control. All of these are safe, natural products available at home and garden centers.

Problem #2 — Powdery Mildew

Powdery mildew

Powdery mildew. Photo: aragriculture.org

The bizarrely cool, rainy summer we’ve experienced in the Southeast this year (sorry, everybody out west) means that if your crepe myrtle is susceptible to mildew, it probably has it. Powdery mildew is a filmy, white fungus that grows on leaves and flower buds. It causes leaves to curl and shrivel. Flower buds drop without opening. Back in the day when we didn’t have resistant selections, powdery mildew was the #1 complaint people had about crepe myrtles.

Solutions: Plant a mildew-resistant crepe myrtle. Almost all of the newer ones are resistant, including those named after tribes of native Americans, such as ‘Acoma,’ ‘Arapaho,’ ‘Catawba,’ ‘Comanche,’ ‘Miami,’ ‘Natchez,’ ‘Sioux,’ ‘Tonto,’ and ‘Zuni.’ ‘Dynamite,’ ‘Early Bird,’ ‘Pink Velour,’ and ‘Red Rocket’ resist it too. If yours isn’t resistant, spray the foliage according to label directions in early summer with neem oil, horticultural oil, Natria Disease Control, Daconil, or Immunox. The first three are natural products. You’ll probably have to spray more than once.

Problem #3 — Cercospora Leaf Spot

Cercospora leaf spot

Cercospora leaf spot. Photo: Steve Bender

Cercospora is a leaf spot fungus that used to be fairly uncommon, but isn’t anymore. Grumpy has a theory that the nearly universal planting of crepe myrtles in the South has made it easy for this fungus to spread. What happens is that in mid- to late summer, angular, brown spots form on the oldest leaves. These leaves then develop fall color prematurely and drop. By fall, the tree may be completely defoliated, except for a few newer leaves at the top. Fortunately, this seems to cause no ill effects the next year.

Solutions: This fungus likes sheltered areas where breezes are blocked and the foliage stays wet for long periods. Grumpy knows this, because the one he planted in front of his house gets eaten up by leaf spot every year, while the one growing in the middle of the lawn is hardly touched. Some websites claim certain selections are resistant, such as ‘Apalachee,’ ‘Catawba,’ ‘Sioux,’ ‘Tonto,’ ‘Tuscarora,’ ‘Tuskegee,’ and ‘Yuma.’ Grumpy has his doubts, because the one that gets devoured every year is ‘Sioux.’ What to do? Plant crepe myrtles in open, sunny spots where air circulates freely. If necessary, spray with Daconil, Immunox, or Natria Disease Control when spots begin to appear.

Problem #4 — No Blooms
No matter where you live in the South, crepe myrtles should have bloomed by now. If yours hasn’t, most likely it’s due to one of three reasons.

1. Your plant is just too small to bloom. Give it time.
2. Your plant isn’t getting enough sun. It likes full sun.
3. Some crepe myrtles bloom better than others. You may have a slacker. If so, replace it with one of the selections named above.

Attention: No ants were harmed in the production of this post.

COMMENTS

  1. Claire

    My crape Myrtle has green fuzzy stuff all over it. Really looks bad.

    January 27, 2016 at 10:14 am
  2. Kathryn King-Metters

    My crape myrtle has some branches shooting straight up from their branches. I rarely prune these as I like the natural growth best. What’s causing this? Should I prune these branches?

    November 21, 2015 at 11:39 am
  3. Steve Bender

    G. Prase,
    The leaves are about to fall off for the winter, so there’s no point in spraying anything now. Next spring, try treating them according to label directions with Bayer Advanced Tree & Shrub Insect Control.

    Oliver,
    Lichens are not the problem. They are harmless. Your crepe myrtles are suffering from something else. As their foliage thins out, they let more sunlight reach the branches, which is what lichens need to grow. The only thing I can suggest at this point is fertilizing your crepes next spring after they leaf out with a tree/shrub fertilizer.

    Susan,
    After your tree leafs out next spring, spray healthy foliage with one of the disease control mentioned above under problem #2.

    November 20, 2015 at 2:11 pm
  4. Oliver

    Just moved to this property in NW Fla.. Crepe Myrtles have lichens all over them barely bloom and seem to be struggling. What can I do. Oliver

    November 18, 2015 at 4:38 pm
  5. G.Prase

    My Crepe Myrtles have black Leaves and are infested with a reddish bug in the shape of a ladybug.I sprayed organic oil,soapy water.They left and came right back.It is very frustrating we like to see the pest be gone for good.

    November 11, 2015 at 3:59 pm
  6. susan mcbeth

    Mine has some kind of mold. Only one or two blooms. Yuk! brown spots on green leaves. New leaves at root are green, but spotted by the time they get grown up the branch. It is Sept. 19, 2015.. OK to cut back now. Is it dead for next year?

    September 19, 2015 at 2:00 pm
  7. Steve Bender

    Delicia,

    That is sooty mold. To get rid of it, follow the directions above.

    September 14, 2015 at 2:27 pm
  8. Delicia Dawn

    My Crepe Myrtles have black branches with white fuzz on them. I live in East Texas.

    September 14, 2015 at 12:44 pm

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