Crape Myrtle Pests

Crape Myrtle has few pests that impact their health and overall growth. When these shrubs and trees are planted in full sun with adequate moisture and soil drainage they are virtually carefree. Sap-sucking insects such as Aphids can take hold and cause issues with new foliage development.

Large populations of Aphids make themselves known by excreting a sticky honeydew sap that attracts other pests such as ants who harvest the sap and sooty molds which rapidly grow anywhere that the honeydew has accumulated.

Japanese Beetles are another pest that can cause damage to the foliage and flowers. The late-blooming Crape Myrtle can be left with no flowers over the course of just a few weeks in mid-summer when Japanese Beetles swarm gardens.

Mature and well-established trees and shrubs are likely to outgrow any foliage damage and often look as good as new the following spring when the new season's growth emerges.  

Aphids

Sap-sucking pests cause direct damage to leaves and tender stems by feeding on the sugars and fluids that circulate and nourish your trees and shrubs. Eventually, damage to the foliage affects the plant's ability to photosynthesize when large portions of the plant are infested.

Aphids exude a sticky substance called honeydew that can cause damage to outdoor furnishings, decks, and the finish of a car over time. Secondary infestations of ants and black sooty mold are drawn to the honeydew which can sometimes be more difficult to control than the initial aphids. 

Treating Aphids on Crape Myrtle

Crape Myrtle is particularly prone to attacks from Crape Myrtle Aphids (Sarucallis kahawaluokalani) during the periods of new growth in the late spring and summer. The aphids are light green in color. Adults are no larger than 1/16 of an inch in length and are able to reproduce a new generation every 10 days, quickly making large populations that cause yellowing and a stippled appearance to the leaves at the points where they feed.

Sticky honeydew and sooty mold may be present when populations are large. Ants may be seen harvesting the honeydew and will act as guards for the aphids to protect their newly found source of food.

Aphids rarely are devastating to fully established and mature trees or shrubs but will cause temporary cosmetic damage. The damaged foliage will regrow either over the course of the summer (for early attacks) or the following spring when new growth emerges. Large trees and shrubs are difficult to treat with horticultural soap sprays although a sharp stream of water from the garden hose may be easier to manage and do a good job of knocking adults off the plant before they can lay more eggs.

Repeat the treatment every few days until no further signs of damage or adult-stage aphids are visible. Prune out large area of damage to physically remove the pests and eggs.  

Preventing Aphids on Crape Myrtle

Cultural methods are the best way to avoid outbreaks of Aphids on your Crape Myrtle trees and shrubs. Ensure that the plants are sited in a location with at least 6-8 hours of full sun exposure with plenty of air circulation between it and neighboring trees or shrubs.

Fertilizing with high-nitrogen feeds encourages denser than normal foliage growth. This fast growth is typically weak and not well supported by the root system making it an easy target for sap-sucking insects.

The adults lay a final stage of eggs near the base of Crape Myrtle to overwinter in leaf litter and mulch. Clean up spent foliage in the fall and make sure that mulching material is kept at least 2-3 inches away from the base of the plant.

Horticultural oils like NEEM may be used early in the spring just at bud break to protect attacks from any hatching aphids. Encouraging natural predators like lady beetles, lacewings, frogs and songbirds also helps to keep populations of pests in check and any damage to a minimum.  

Japanese Beetles 

Japanese Beetles cause some of the most destructive damage to ornamental plants, just as they are reaching their stride in early summer. From late May to late July the adult Japanese Beetle emerges from lawns in most areas of the United States. They feed on foliage and flowers of susceptible plants for 6 weeks before settling down and laying the next season's eggs in well-tended and watered lawns.

The grubs that emerge feed on the roots of the turf grass causing yellow and brown dead patches throughout the fall and winter months.

Unfortunately, Crape Myrtle (along with Roses and Crabapple trees) are some of the most appealing plants for Japanese Beetles. Small amounts of the beetle typically do not cause much damage, but they are highly mobile and will fly great distances to find other Japanese Beetles and just the type of plant they want to feed on. 

Treating Japanese Beetles on Crape Myrtle

The best way to control small outbreaks of Japanese beetles is to handpick them from your plants and deposit them in a bucket of soapy water to kill them. This is a process that needs repeating every day through the “feeding season”. Horticultural sprays are marketed to kill off the adult beetles but only work for 1-2 weeks per treatment and will require reapplication.

Smaller trees and shrubs may be covered with fine insect netting or lightweight horticultural fleece to temporarily provide a physical barrier to the beetle. The whole plant must be wrapped securely to prevent any beetles from getting up under the fabric. Crape Myrtle that is fully established and mature are not often permanently damaged and will recover when new growth emerges.  

Preventing Japanese Beetles on Crape Myrtle

A very effective method of controlling Japanese Beetles in your landscape is to drench your lawn with a milky Spore preparation late in the summer as the grubs hatch and begin to feed. Milky Spore is a bacteria that targets only the grub stage of Japanese beetles and causes them to die off before pupating into the adult stage.

It can be found at most garden centers and is completely safe for home gardeners to use. Monitor your lawn for dead or yellowing patches over the winter months to keep an eye on grub populations.

Hormone traps can be useful for monitoring when the beetles are active. Locate the hormone traps at least 50 ft away from plants that you want to protect and dispose of them as soon as it fills. This can be every day at the peak of the season. Placing the traps too close to the plants will have the opposite effect and let any and all Japanese Beetles where the tastiest meals are. 

Common Crape Myrtle Pest Chart

Sources:

“Guide to Insects of Woody Plants”, the University of Kentucky Entomology. www.uky.edu/ag/entomology