Can you tell me what is wrong with my crape myrtles?

Published 6:48 pm Thursday, August 9, 2018

Two calls came in this week regarding crape myrtle issues. There are very few pest or disease issues that occur with crape myrtles. Crape myrtles are one of the top planted ornamental trees in the Southeast and for good reason. They are a hardy tree with over 90 cultivars. Cultivars vary in size from 4 feet tall to over 40 feet tall. There are several flower colors and one to five stems or trunk configurations.

The number one problem with crape myrtles is crape murder! This is the complete topping of trees where the foliage is completely cut off. The practice of topping stresses the tree due to decreased photosynthesis, opens the tree up to sun scald and alters growth pattern in response to this stress. Topping results in an unnatural shape, delayed flowering, less flowering, shortened flower period, weak branches, increased suckering and could lead to higher instance of freeze, killing the trees. Many of the crape myrtles that were “murdered” this past season died from cold damage.

There are a few insect pests that hinder crape myrtles. Crape myrtle aphids are the most prevalent. Aphids over-winter in the tree and populations explode in the spring. Aphids feed on sap from the tree and secrete a sticky, sweet substance called honeydew. Honeydew then leads to a secondary fungal infection, called sooty mold, that turns the leaves and branches black like they have been covered with soot from your chimney. A hard water spray or insecticidal soap will help knock down aphid populations to manageable levels for beneficial insects to keep in check. Another, newer pest is crape myrtle bark scale. This is a scale insect that first congregates around the branch crotches, then covers the branches. These insects also feed on the sap of the tree and secrete honeydew, therefore opening the door for sooty mold as well. Several applications of horticultural oil in the dormant season will suffocate scale insects. Japanese Beetles will chew on the leaves and flowers of the trees causing aesthetic damage. A pheromone trap will work best for control.

There are even fewer diseases that hinder crape myrtles in the landscape. Powdery mildew is a fungal disease that covers the leaves with a white powder, brought on by humid nights in the spring. Proper pruning to open up the inner canopy of the tree and increase airflow is the best method to guard against powdery mildew. Remove branches that are dead, diseased and damaged, any cross-over branches and all suckers.

Cercospera leaf spot is an occasional disease of crape myrtles that appears during periods of warm, moist weather. Leaf spots are yellow, appear on the upper leaf surface with white-grey sporulation on the underside of the leaf. Spots range in size from 1/8 to 1/4 inch in diameter. This disease can result in near complete defoliation in late summer. Control can be achieved through proper pruning. If severe, myclobutanil or thiophanate-methyl fungicides can be applied according to label recommendations.

If you have a question to submit please email Gene Fox at Now is the time to plant your fall garden! If you are having trouble with growing in your home landscape, call the Beaufort County Extension office and speak to an Extension master gardener volunteer, Mondays and Wednesdays between 10 a.m. and noon at 252-946-0111.

Gene Fox is the area agriculture and consumer horticulture agent for Beaufort, Hyde, Tyrrell and Washington counties.