Crepe Myrtle Diseases and Pests: How To ID, Prevent & Treat

Possible rephrasing:

Crepe myrtle trees are highly desirable for their stunning and long-lasting flowers when used in landscaping. However, like all plants, they are susceptible to various diseases and pests.

This article provides a comprehensive guide to identifying, preventing, and treating the most common issues that can affect the health and beauty of your crepe myrtle trees.

Troubleshooting issues is definitely important, but there’s a lot more to learn! Be sure to read my detailed Crepe Myrtle Guide to ensure you’re doing all you can to help your tree flourish.

Crepe Myrtle Diseases

Crepe myrtle trees can be affected by several diseases. Early identification and treatment can help maintain the health and longevity of these beautiful trees.

1. Powdery Mildew

Powdery mildew is a common fungal disease that appears as a white or gray powdery substance on the leaves and buds of the crepe myrtle. It can cause the leaves to curl and may inhibit blooming.

  • Prevention: Ensure your crepe myrtle is planted in a well-ventilated area with plenty of sunlight, as the fungus thrives in damp, shaded areas. Avoid overhead watering to minimize leaf wetness.
  • Treatment: Use a fungicide specifically designed to treat powdery mildew. This one works well. Apply it as soon as you notice the first signs of the disease.

2. Cercospora Leaf Spot

Cercospora leaf spot is a fungal disease that causes small, circular brown or black spots on the leaves of the crepe myrtle.

Over time, these spots can cause the leaves to yellow and fall prematurely.

  • Prevention: Regularly clean up fallen leaves, and prune any infected branches to prevent the spread of the fungus.
  • Treatment: Apply a fungicide that is effective against leaf spot diseases. It’s best to apply it in the early stages of the disease for the best results.

3. Sooty Mold

Sooty mold is a type of fungus that appears as a black, soot-like covering on the leaves, stems, and flowers of the crepe myrtle.

It is often a secondary issue, resulting from an infestation of pests like aphids or scale insects that excrete a sweet substance called honeydew on which the fungus grows.

  • Prevention: Regularly monitor your crepe myrtle for pests, and treat them promptly to prevent the development of sooty mold.
  • Treatment: Control the underlying pest problem to stop the production of honeydew. The sooty mold will gradually go away once the honeydew source is removed.

4. Phyllosticta

Phyllosticta is a fungal disease that causes small, brown spots with yellow halos on the leaves of the crepe myrtle. Over time, these spots can cause the leaves to yellow and fall prematurely.

  • Prevention: Regularly clean up fallen leaves, and prune any infected branches to prevent the spread of the fungus.
  • Treatment: Apply a fungicide, like this one, that is effective against leaf spot diseases. It’s best to apply it in the early stages of the disease for the best results.

5. Phytophthora Root Rot

Phytophthora root rot is a serious disease that affects the roots of the crepe myrtle.

Symptoms include wilting, yellowing leaves, and stunted growth. In severe cases, it can cause the death of the tree.

  • Prevention: Plant your crepe myrtle in well-draining soil, and avoid overwatering. Phytophthora thrives in waterlogged soil.
  • Treatment: If you suspect your tree has root rot, consult with a professional arborist. They may recommend a specific fungicide or other treatment options.
Pink flower panicle of crepe myrtle up close.

Crepe Myrtle Pests

Crepe myrtle trees can also be affected by a variety of pests. Here are some of the most common ones and how to deal with them.

1. Crepe Myrtle Bark Scale

Crepe myrtle bark scale is a small insect that appears as a white or gray waxy coating on the branches of the crepe myrtle.

They suck the sap from the tree and excrete honeydew, which can lead to the growth of sooty mold.

  • Prevention: Regularly inspect your crepe myrtle for signs of these pests, especially in the early spring when they begin to feed.
  • Treatment: Use a systemic insecticide containing dinotefuran or imidacloprid that is absorbed by the tree and kills the scale insects when they feed.

2. Aphids

Aphids are small, soft-bodied insects that can be green, yellow, black, white, or red.

They suck the sap from crepe myrtle leaves, causing them to curl and yellow. Aphids also excrete honeydew, which can lead to sooty mold.

  • Prevention: Encourage natural predators like ladybugs and lacewings in your garden, which can help control aphid populations.
  • Treatment: Insecticidal soaps or oils can be effective against aphids. For severe infestations, a systemic insecticide may be necessary.

3. Japanese Beetle

Japanese beetles are metallic blue-green insects that can cause significant damage to crepe myrtles by eating the leaves and flowers.

  • Prevention: Regularly inspect your trees during the summer months when these beetles are most active.
  • Treatment: Hand-picking can be effective for small infestations. For larger infestations, consider using a pesticide that is specifically designed to control Japanese beetles, like this one.

4. Spider Mites

Spider mites are tiny, spider-like pests that can cause the leaves of your crepe myrtle to become speckled, yellow, and eventually fall off.

Fine, silvery webbing is a telltale sign that the pests are present and active.

  • Prevention: Keep your trees watered well as spider mites often target stressed trees.
  • Treatment: Insecticidal soaps or oils can be effective against spider mites. For severe infestations, a miticide may be necessary.

5. Whiteflies

Whiteflies are tiny, white-winged insects that suck the sap from crepe myrtle leaves, causing them to yellow and drop. Like aphids, they excrete honeydew, leading to sooty mold.

  • Prevention: Encourage natural predators in your garden, such as ladybugs and lacewings.
  • Treatment: Insecticidal soaps or oils can be effective. For severe infestations, consider a systemic insecticide.

6. Mealybugs

Mealybugs are small, white, cottony pests that suck the sap from crepe myrtle, causing leaves to yellow and drop. They also excrete honeydew, leading to sooty mold.

  • Prevention: Regularly inspect your trees for these pests and remove them promptly.
  • Treatment: Insecticidal soaps or oils can be effective. For severe infestations, consider a systemic insecticide.

7. Flea Beetles

Flea beetles are small, jumping beetles that chew small holes in the leaves of crepe myrtle.

  • Prevention: Keep your garden clean of debris and weeds that can harbor these pests.
  • Treatment: Use a pesticide labeled for flea beetles, following the manufacturer’s instructions.

8. Borers

Borers are insects that tunnel into the trunk and branches of crepe myrtle, causing wilting and dieback.

  • Prevention: Keep your trees healthy because borers often target stressed trees.
  • Treatment: If you notice borer activity, consult with a professional arborist for treatment options.

9. Bark Lice

Bark lice are harmless insects that create a silken web over the bark of Crepe Myrtle. They feed on algae, fungi, and other materials on the bark.

  • Prevention: No prevention is necessary as these insects are beneficial.
  • Treatment: No treatment is necessary. If the webbing is unsightly, it can be rinsed off with a strong jet of water.

10. Ants

Ants are attracted to the honeydew excreted by aphids and scale insects. While they don’t harm the tree directly, they can protect these pests from their natural predators.

  • Prevention: Control honeydew-producing pests to make your trees less attractive to ants.
  • Treatment: If ants are a problem, consider using ant baits or other control methods.

Closing Thoughts

Maintaining the health of your crepe myrtle trees involves regular monitoring for signs of diseases and pests.

Early identification and treatment can prevent minor issues from becoming major problems.

With the right care and attention, your crepe myrtle trees can continue to provide beauty and shade for many years to come.

Remember, when in doubt, don’t hesitate to consult with a professional arborist or your local extension service.

They can provide you with the most accurate information and treatment options for your specific situation.