Crape Myrtle Bark Scale

The crape myrtle is a popular tree in the Memphis area thanks to its beauty, variety and hardiness. Until recently, the greatest threat to the crape myrtle was poor pruning known as “crape murder.” However, a scale insect introduced to the Memphis area around 2012 is causing major problems.

Crape Myrtle Bark Scales look like quite flecks, and they leave a black moldy residue on the bark.

Crape Myrtle Bark Scale (center) and moldy residue (left)

The crape myrtle bark scale attaches itself to the trunk of the tree and sucks nutrients straight from its bark. At the end of its life cycle, the scale produces around a hundred eggs that will become the next generation. With such a high reproduction rate, the scales can become problematic very quickly.

While not sufficient to kill the tree, the loss of nutrients can cause the tree to have less-brilliant blooms or even to not bloom at all. Waste from the scale is also sufficient to leave a black moldy residue on the tree’s bark, sometimes completely replacing its usual brown or tan color. Droppings from the scale can also cover leaves and anything under the tree with a waxy, sticky coating.

Moldy residue on a plant beneath a crape myrtle left by the bark scale

Moldy residue left on a plant beneath a crape myrtle

In our experience, the scale mostly affects older trees rather than those that are young and still rapidly developing.

The scale is difficult to control, but consistent treatment can restore your trees’ beauty. Below are the treatment methods recommended by the Texas A&M Extension service. Herbi-Systems offers dormant oil and systemic insecticide treatments as part of our Tree and Shrub service. If you are not currently part of the program, please request a free estimate and select that you would like an estimate for tree and shrub services. If you are a current customer and are noticing scales on your crape myrtles, let us know so that we can give them special attention!

Treatment Options

Trunk Wash

Wash affected areas of the trunk and limbs with a soft brush and a mild solution of water and dishwasher detergent. This removes egg masses, scales and black mold that grows on scale waste. Not only will the tree look better, insecticide treatments will be more effective. Removing loose pieces of bark will also eliminate areas where the scales can “hide” and escape treatment.

Dormant Oil

The dormant oil treatment offered with our tree and shrub program between fall and spring effectively “drowns” the scales and prevents them from reproducing. This treatment alone can not eliminate all scales, but it makes them much easier to control.

Systemic Insecticide

An insecticide applied to the root zone of the tree controls the scales by making the scales’ food source, the tree’s sap, unsafe to feed on. Like the dormant oil, systemic treatment can not kill all the scales, but it will make them more manageable.

Photos

These photos were taken in the Memphis area by a Herbi-Systems tree and shrub care expert.

Close-up view of crape myrtle bark scale - they look like white, cottony flecks.

A close-up view of the scale

Crape myrtle bark scale hides in branch crotches

Scales hide in branch crotches

Sticky residue on plant beneath a crape myrtle left by crape myrtle bark scale

Sticky residue on plant beneath a crape myrtle

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