Crape myrtle shrubs (Lagerstroemia spp.) are popular for their colorful foliage and Southern temperament. However, crape myrtle plants can suffer problems like aphids or powdery mildew. In this article, we’ll look at eight common crape myrtle pests and diseases and how to deal with them.
8 Common Crape Myrtle Pests and Diseases
Aphids are little black or green sap-sucking insects that gather in large numbers on the undersides of leaves. Aphid infestations can affect crape myrtles by causing stunted or misshapen growth. Aphids also produce honeydew, a sticky substance that can cause the growth of sooty black mold.
Eliminate aphids using insecticidal soap, biological controls, or horticultural oils like neem oil. You can also blast your crape myrtle with a hose to dislodge aphids quickly.
2) Asian Ambrosia Beetles
Asian Ambrosia beetles are small reddish-brown beetles that bore into crape myrtle trunks to lay their eggs. To feed their larvae, female beetles use a fungus that impairs the plant’s ability to circulate water.
Asian Ambrosia beetles are a relatively new pest but have already started attacking crape myrtles. Symptoms include wilting leaves and white dust left behind when the beetles burrow into the trunk.
Insecticides can’t stop large Asian Ambrosia beetle infestations, so affected branches must be removed. Crape myrtles that get enough water have better defenses against these beetles.
3) Bark Scale Insects
Bark scale insects are another new pest that attacks crape myrtles. Thankfully, these attacks won’t usually kill the plant. Bark scale insects are typically found in crevices on the trunk and don’t appear on the leaves.
These insects secrete honeydew, which leads to black sooty mold that causes misshapen growth. Bark scale insects target crape myrtles growing in the shade, so position your plant in full sun. Eliminate bark scale insects using insecticidal soap or horticultural oils.
4) Japanese Beetles
Japanese beetles are common crape myrtle pests with brown bodies and metallic green heads. Adults consume crape myrtle leaves and flowers, while the larvae consume the roots. Japanese beetles lay their eggs in the soil, allowing the larvae to survive during the winter.
Eliminate Japanese beetles using horticultural oils or insecticidal soap. Pick off any adults you find and drown them. You can also buy Japanese beetle traps that attract these pests, so place these well away from your crape myrtle.
5) Leaf Spot
Cercospora leaf spot is a fungal disease that attacks crape myrtles. This leaf spot disease is more prevalent in warm, humid conditions. Infected leaves display yellow or black spots on the top and grayish-white fungus underneath.
If left untreated, the Cercospora leaf spot causes crape myrtles to drop their leaves during the summer. This disease can be eliminated using organic fungicides. Giving your crape myrtle plenty of space and good air circulation helps stop the disease from infecting your plant.
6) Powdery Mildew
Powdery mildew is a fungal disease that thrives in humid conditions. The main symptom is a buildup of powdery white patches on the leaves of your crape myrtle. Other symptoms include curled or discolored leaves.
Remove any infected leaves as soon as you see them. Make sure that your crape myrtle has plenty of space around it to promote good air circulation. Avoid overwatering your crape myrtle to reduce humid, moist conditions. Remove leaf debris as powdery mildew survives the winter on fallen leaves.
7) Scale Insects
Scale insects are sap-sucking insects with waxy armored shells. These pests are often seen on crape myrtle leaves. Other symptoms include white eggs underneath the leaves and deposits of honeydew, which lead to black mold.
Use horticultural oils, insecticidal soap, and biological controls to eliminate scale insects. Larger infestations will need to be eliminated using organic pesticides.
8) Spider Mites
Spider mites are annoying pests that thrive in hot summer conditions. These pests consume chlorophyll within crape myrtle leads, leading to stunted or distorted growth. Other symptoms include white webs around the leaves and black or yellow leaf spots.
The best way to eliminate spider mites is to use horticultural oils or insecticidal soap. Biological controls also work well. Small spider mite infestations aren’t a severe problem for crape myrtles, but large infestations must be dealt with.
How to Care For Crape Myrtle
Crape myrtles thrive in Zones 6 to 9 and require sheltered locations to protect them from strong winds. Most crape myrtles can survive winter temperatures as low as -5ºF. In colder climates, grow crape myrtles in containers and protect them by wrapping them in fleece or bringing them indoors.
Crape myrtles need at least six hours of full sun every day. The morning sun is preferable to direct afternoon sunlight, which is more intense. South or west-facing locations provide crape myrtles with the ideal amount of sunlight.
Crape myrtles require well-draining soils that still hold a bit of moisture. They can survive in nutrient-poor soils and are drought-tolerant once established. Crape myrtles prefer slightly acidic soils with pH levels between 5.0 and 6.5.
Water established crape myrtles every two weeks or so to keep the soil moist and more frequently in hot, dry conditions. Water newly planted crape myrtles once or twice a week for the first couple of years. This helps the plant establish a good root system.
Feed older crape myrtles once during the spring with a slow-release fertilizer. This provides plenty of nutrients for the development of new leaves and flowers. Fertilize newly planted crape myrtles once a month during their first growing season.
Pruning & Trimming
Crape myrtles vary in size, impacting how often you want to prune them. Dwarf varieties won’t need much pruning because they only grow between 2 and 6 feet tall. However, some types of crape myrtle grow as shrubs or small trees that reach approximately 30 feet tall and 15 feet wide.
Rather than pruning too often, assess your garden first and determine what type of crape myrtle you can accommodate. Choose a crape myrtle that stays at a manageable size for your space. This allows you to reduce the pruning you’ll need to do.
Crape Myrtle Pests and Diseases FAQs:
How do I prevent crape myrtle pests and diseases?
In my experience, prevention measures vary depending on the specific pest or disease, but generally, you should practice good sanitation, avoid over-fertilization, and provide proper watering and drainage, to mitigate the chances of pests or diseases.
What should I do if I notice signs of a pest or disease on my crape myrtle?
First, identify the specific pest or disease and then determine the appropriate treatment method. Treatment options may include controls, such as pruning and sanitation, or chemical controls, such as insecticides and fungicides.
How can I tell if my crape myrtle has a pest or disease problem?
Look for physical signs such as leaf curling, discoloration, or spotting, as well as unusual growth patterns or damage to the bark or stems. You may also notice the presence of insects or webbing on the plant.
Are crape myrtle pests and diseases harmful to humans or pets?
Most crape myrtle pests and diseases are not harmful to humans or pets, but it is always a good idea to wash your hands thoroughly after handling any potentially contaminated plant material and wear protective gloves when dealing with affected areas.
Crape myrtles can be infected by diseases like Cercospora leaf spot or powdery mildew. Crape myrtles can also be attacked by pests such as aphids and Japanese beetles. Most crape myrtle problems can be solved using horticultural oils, insecticidal soap, or organic fungicides.
For more, see our in-depth guides to crape myrtle deer resistance and whether crape myrtles are toxic to humans and animals.
Edd is a budding content writer and gardener living in the United Kingdom. He has a bachelor's degree in Creative and Professional Writing and has written for several gardening publications online. He is passionate about nature and sustainability with a focus on gardening and wildlife.
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