A Problem for Crapemyrtles
A new pest that attacks crapemyrtles has made its way into our area. Based on reports we’ve been getting from homeowners and landscape professionals, Crapemyrtle Bark Scale is becoming well established in the Payne County area. This pest is significant as it causes a slow but steady decline in the health of one of our best summer flowering shrubs.
It is difficult to control as our options are limited by at least two factors. Scale insects in general are resistant to control because of the waxy cotton-like coating that protects them from most sprayable contact insecticides. Soil applied systemic insecticides, while offering some control, are NOT recommended because of the potential for moving into the long lasting flowers, causing harm to bees or other pollinators.
However, the news is not all bad. There are some control options and February is the best time to initiate them. To check for these pests, look for small white spots about the size of this capital O. While they can be located on any part of the plant, they tend to gather in the narrow angle of branches. If you have a heavy infestation, clusters of old scales make take on more of a grey color, looking almost like the crapemyrtle trunk has warts. Once you’ve seen this pest one time, you will have no trouble identifying it.
If you confirm your plants do have the scale, apply dormant oil this month before new leaves begin to emerge. Follow label directions carefully, especially in regards to rate, coverage, and air temperature.
When spring pruning time comes, aggressively prune away all the affected branched and dispose of them. Watch closely throughout the growing season for signs of reinfestation and use a soapy scrub brush to remove any new insects. For maximum effectiveness, you may want to follow this process with an application of a broad spectrum contact insecticide. Remember that dormant oil is defined by its time of use, i.e., when the plants are dormant. Attempting to retreat with dormant oil after the leaves have opened up will cause significant damage.
Oklahoma State University has a recent Pest-E-Alert on this topic. Vol. 16 No. 17 (PDF). You can also learn more by visiting Oklahoma Gardening’s YouTube channel show #4411.
For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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