Crape Myrtle Bark Scale (CMBS): What You Need to Know
CMBS, like other scales, are tiny insects that feed on the sap of plants and exude a sweet, sticky substance called honeydew, promoting the growth of black sooty mold. Crape myrtles are the only host of this pest. Left untreated, infestations will turn the branches of Crape Myrtle, and nearby surfaces, black in a short time causing an unsightly appearance and a decline in the health of the tree. Infestations are rarely fatal, but can be difficult to control due to the waxy covering they create from the cellulose in the sap.
CMBS is a felt scale due to the fuzzy white appearance of its waxy coating. It settles in crevices and branch/twig unions on the trunks and canopies of crape myrtle trees and shrubs. The sticky honeydew and black sooty mold are often noticed first, usually months after the initial infestation. This characteristic can be misleading since they are byproducts of all sap-sucking insects, including aphids, which are common to crape myrtles but controlled with the same treatments.
First, consider the environmental ramifications. Crape myrtles offer little to our local ecology because they are not native to this area. Besides requiring considerable maintenance, water, nutrients, and space, they attract many pests besides CMBS. Unfortunately, there is nothing quite like a crape myrtle, but a wide variety of native alternatives, like beautyberry, buckeye, fringe tree, clethra, locust trees, redbud, yellowwood, and sourwood, will better align with our reforestation efforts. If replacing your crape myrtle and chemical treatment is out of the question, prune out infestations and use a powerful stream of water or a soft scrub brush for physical removal. Improving overall health of the tree and attracting ladybugs with a wide variety of native flowers will improve nature’s control mechanisms.
This will require multiple pesticide applications. Environmentally friendly treatments with horticultural oils, insecticidal soaps and insect growth regulators will provide some control while preserving beneficial insects. It is best paired with a systemic insecticide root drench to limit exposure to beneficials. Otherwise, many pesticides are labeled for scale.
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