Crape Myrtle Leaves Turning Yellow

Crape Myrtle Leaves Turning Yellow

Your crape myrtle leaves may turn yellow because an environmental factor is causing the plant stress. In order to fix the problem, you need to identify the cause.

The most common causes of yellowing crape myrtle leaves are Cercospora leaf spot, toxicity, bacterial leaf scorch, living conditions, pests, powdery mildew and natural yellowing.

In this article, we will discuss the different causes of yellowing crape myrtle leaves and how to remedy each one.

Why are my crape myrtle leaves turning yellow?

Cercospora leaf spot

If your crape myrtle’s leaves are turning yellow and falling off, one of the most common causes is Cercospora leaf spot. This disease is caused by the fungus Cercospora lythraceae. This disease may be hard to diagnose, because the fungus likes to attack during the autumn when the tree is naturally changing color and dropping its leaves. You may think it is just your crape myrtle being normal, but it is actually the fungus damaging your plant.

Cercospora leaf spot starts out as quarter-inch brown spots on the leaf surface, but over time the leaves will twist and distort. The spots will enlarge and turn red or yellow, and the leaves will then fall off. The spotting usually starts at the base of the plant and spreads upward towards the younger leaves.

There are cultivars of crape myrtle that are resistant to fungi. You can choose to plant those and space them out widely so that they do not get infected easily. Apply fungicide every one to two weeks when you see any spotting appear.

Toxicity

The crape myrtle’s leaves can also turn yellow due to toxicity caused by excessive herbicides, pesticides or nutrients. The foliage will turn yellow, wilt and die. The branches may die back, and the tree’s weakened state will make it susceptible to diseases and pests.

Plant the crape myrtle in well-draining soil so that the roots develop well. Use herbicide sparingly and try not to spray it on windy days, because it can make its way onto your plants and harm them.

Bacterial leaf scorch

This disease is common among shade trees and is caused by the Xylella fastidiosa bacterium. The early stages of the disease can be hard to catch because the most obvious signs are only noticeable when the infection has become serious. At this stage, the tree is often close to death and is unsalvageable. 

The first signs of leaf scorch are browning and dying leaves that will eventually drop off. It will start at the edges, turning them brown while leaving the center of the leaf green.

There are no treatments for bacterial leaf scorch, but you can still get a few years from your tree before it finally succumbs to the disease. Once leaf scorch has been diagnosed, death will occur within about five to ten years. Make sure you provide supplemental water, fertilize it in the spring, and prevent weeds and competitive plants from growing in the tree’s root zone. This lessens the stress on your tree and prolongs its life.

Living conditions

The crape myrtle is very sensitive to its living conditions. If the conditions around it vary even a little from the ideal, the plant will have problems with its foliage. Crape myrtles require a bright and sunny location, and soil that is well-draining and moist. The more established the plant, the more drought-tolerant it is, but it still needs to be watered during extended dry periods. Remove any spent flowers on the tree to encourage new blooms. Prune any dead or diseased branches in the late winter or early spring to promote new growth.

Pests

One of the most common pests of the crape myrtle is the crape myrtle aphid. These insects are very small and have a yellow-green body with back spots. Like other aphids, they pierce the leaf of the plant to consume the sap. Even with their small size, they are able to stunt the plant’s growth and distort the leaves in small infestations. Large infestations produce yellow leaves, early leaf drop and sooty mold.

You can control these insects by encouraging their natural enemies, such as ladybugs. You can also use neem oil to kill the insects on the leaves. Apply the neem oil once a week for a month to make sure all the insects have been killed.

Powdery mildew

This fungal disease causes cottony white patches to appear on the crape myrtle’s leaves. If the plant is heavily infested by the mildew, the shoots and leaves may distort and twist. It also causes bud abortion which keeps the plant from blooming. This disease occurs most commonly during April, and is not easily noticed until May or even June.

You can combat powdery mildew by providing plenty of ventilation around the plant, not allowing any water to remain on the leaves overnight, and applying fungicide on the plant once a week until the middle of summer.

Natural yellowing

Sometimes the reason for the crape myrtle’s leaves turning yellow is benign. Some species of crape myrtle have leaves that turn yellow in the autumn, so the yellow leaves on your crape myrtle may just be the true color of the plant’s leaves.

There is nothing you need to do about this except admire the variety of colors that nature is able to produce.

Conclusion

Crape myrtle leaves turn yellow due to environmental factors that cause the plant stress. You can remedy the problem by correctly identifying the cause of the discoloration.

The most common causes of yellowing crape myrtle leaves are Cercospora leaf spot, toxicity, bacterial leaf scorch, living conditions, pests, powdery mildew and natural yellowing.

Image: istockphoto.com / John M. Woodcock