The Crepe Myrtle (Lagerstroemia indica) is a beloved ornamental tree, celebrated for its vibrant, long-lasting summer flowers and attractive exfoliating bark. A common frustration occurs when the lush foliage begins to show signs of distress, appearing chewed, spotted, or sticky. Identifying the precise cause of this damage is the first step toward effective treatment, as the symptoms of different pests can sometimes be confused.
Common Pests That Chew Holes in Leaves
The most obvious signs of insect activity are physical holes or a ragged, tattered appearance on the leaves, which indicate a chewing pest. These insects consume the leaf tissue directly, leaving behind telltale patterns of damage.
Japanese beetles (Popillia japonica) are one of the most recognized culprits, easily identified by their metallic green bodies and coppery-brown wing covers. Adult beetles feed on the upper surface of the leaves, chewing the tissue between the veins. This feeding habit is known as skeletonization, which leaves the foliage with a distinctive, lace-like or skeletal appearance. A heavy infestation can make the tree look scorched from a distance.
Caterpillars and webworms also cause significant, visible damage by physically consuming the leaves, often resulting in large, irregular holes or completely missing portions of the foliage. These larval stages of moths and butterflies can sometimes be found clustered together, occasionally in silken webs. Healthy, established Crepe Myrtles can often withstand minor infestations and recover the following season. Another pest to look for is the metallic flea beetle (Altica spp.), which creates small, irregular, rounded holes or shallow pits as it feeds on the leaf surfaces and edges.
Identifying Damage from Sap-Sucking Insects
Not all leaf damage comes from chewing; a different group of insects uses piercing-sucking mouthparts to feed on the plant’s internal fluids. This type of feeding does not create holes but instead results in visual distress and secondary issues.
The most common sap-sucking pest is the Crepe Myrtle aphid (Tinocallis kahawaluokalani), a small, pale yellowish-green insect that targets tender new growth. As aphids feed on the sugary sap, they excrete a clear, sticky waste product known as honeydew. This honeydew coats the leaves and branches beneath the feeding site, giving the foliage a glossy, sticky feel.
The presence of honeydew almost inevitably leads to the development of sooty mold, a non-parasitic fungus that grows exclusively on the sugary residue. Sooty mold appears as a black, powdery coating that covers the affected leaves, stems, and even the surrounding ground. While the mold itself does not infect the plant tissue, a thick layer can significantly block sunlight, reducing the plant’s ability to photosynthesize.
Another serious sap-feeding issue is the Crepe Myrtle Bark Scale (CMBS), which appears as white or gray, felt-like encrustations, primarily on the bark and twigs. However, this scale also produces copious amounts of honeydew, causing sooty mold to accumulate on the leaves, branches, and trunk. CMBS infestations can cause reduced flower size and abundance, early leaf drop, and overall reduced plant vigor.
Effective Management and Control Strategies
Successful management of Crepe Myrtle pests involves an Integrated Pest Management (IPM) approach, combining preventative and targeted actions. Beginning with cultural practices, the tree’s overall health can be strengthened by ensuring it is planted in full sun with good air circulation and watered deeply but infrequently. Healthy plants are better equipped to withstand and recover from minor pest damage.
Mechanical and Organic Control
The first line of defense against both chewing and sap-sucking pests is often mechanical or organic control. Japanese beetles and caterpillars can be manually removed, especially in the morning when they are less active, and dropped into a container of soapy water. A strong, direct jet of water from a garden hose can physically dislodge soft-bodied pests like aphids from the leaves. This is a safe, non-chemical solution that should be repeated regularly.
Chemical Control
For more persistent soft-bodied insects, such as aphids and the mobile crawler stage of scale, horticultural oils or insecticidal soaps can be applied directly to the affected areas. These products work by smothering the pests and are generally safer for beneficial insects when used correctly. For severe or deeply established infestations, like with CMBS, systemic insecticides may be necessary. Systemic treatments are absorbed by the roots and move throughout the tree, offering long-term protection, but they must be used judiciously and strictly according to product label instructions.