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

August 22, 2013 | By | Comments (162)
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. Steve Bender

    Teresa,
    This is a fungus called black mold that grows on the sticky honeydew secreted by sucking insects such as aphids. Kill the insects and the mold goes away. Spray your tree with neem oil, horticultural oil, or insecticidal soap according to label directions.

    September 28, 2016 at 8:09 am
  2. Jan Champagne

    I live in Northeast Pennsylvania. I planted a Crape Myrtle two,years ago. I have seen many planted and thriving in our area. I do put a layer of mulch and wrap it for winter protection. The question I have is both years, I am not sure whether I got to it in time with protection, but the leaves had already dried up and dropped off. The first year, the plane came back at the ground area, the second year, the leaves came back on the woody stems and it bloomed a little. Is it normal for the leaves to just dry up and fall off? Thank you.

    September 25, 2016 at 9:21 am
  3. leonard williams

    my crepe myrtle has leaves falling and on all the limbs and main trunks are whit e spots. looks like tiny mot h balls all over them, hope my tree isn’t dieing.

    September 19, 2016 at 10:48 am
  4. Grumpy Gardener

    Teresa,
    This is probably black mold that’s growing on honeydew secreted by feeding aphids. Spray your plant according to label directions with horticultural oil.

    Sheree,
    This must be due to growing conditions, but I can’t give a specific answer.

    September 17, 2016 at 4:36 pm
  5. Teresa Myers

    What is wrong with my Crape myrtles?
    The bark is black

    September 17, 2016 at 3:18 pm
  6. Sheree Kristinek

    My crepe myrtle has buds all over it but they won’t open. This has happened for several years.

    September 3, 2016 at 2:09 pm
  7. Grumpy Gardener

    Carolyn,
    The white film is powdery mildew. See problem #2 above.

    Sallie,
    The gardenias have black mold. See problem #1 above.

    August 31, 2016 at 11:13 am
  8. carolyn wrigley

    My plant is trying to bloom and has some but the booms have a white film over them. What can I do and what is it

    August 23, 2016 at 12:25 pm
  9. Sallie

    what about gardinas plants hat have black leaves what do you put on them? I live in Central FL

    August 20, 2016 at 1:57 pm
  10. Steve Bender

    Bruce,
    Yes.

    August 18, 2016 at 1:34 pm
  11. G. Bruce Makowski

    My crepe myrtle is planted in the open sun with lots of breeze and its leaves are turning color and dropping? Do you think Cercospora leaf spot is the problem?

    August 13, 2016 at 9:09 pm
  12. Grumpy Gardener

    Martha,
    I’d move your crepe myrtle to a spot with full sun this fall. In its place near the house, what about a Japanese maple?

    August 11, 2016 at 10:19 am

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