There is currently no data or research that suggests pruning or power washing as an effective management strategy for crapemyrtle bark scale. However, anecdotal experience suggests that power washing can help remove adult scales from the trees and loosen the sooty mold. Scrubbing the tree branches and trunks with a brush and soapy water can help remove crapemyrtle bark scale adults and remove sooty mold.
Several beneficial insects have been observed feeding on crapemyrtle bark scale. The most notable natural enemies are ladybeetles, namely Hyperaspis and Scymnus species. Preliminary findings from a trial conducted by Dr. Mike Merchant in Dallas suggests that ladybeetles can provide about 75% suppression of scale insects in the landscape. In order to maintain longterm control of crapemyrtle bark scale, homeowners and landscapers should use insecticides that will not harm predatory insects.
Chemical controls must be applied early to prevent formation of new adults. Once adults (white spots) are on the trees, removal of adults can be challenging because they do not feed, are protected with a waxy layer, and the spots can remain on the tree even if the adult is no longer alive. As a result, current management recommendations involve early (March – May) applications of either systemic controls or contact insecticides.
Soil drench of imidacloprid or dinotefuran at the labelled rate were highly efficacious at managing the scale populations when applied early in the season. Apply soil drenches early spring, just as crapemyrtle leaves begin to bud out and are taking up water from the ground.
Current contact insecticides are not available to homeowners, so you may need to contact a landscaper or have a pesticide applicators license to acquire these products. So far, trials have demonstrated excellent ability to control crapemyrtle bark scale using bifenthrin, pyriproxyfen, or buprofezin at labelled rate applied twice on a 7 – 14 day interval. Preliminary trials with dinotefuran as a bark spray (with capsil) has demonstrated similar control of crapemyrtle bark scale as a soil drench over the period of 19 weeks.
Limited or Ineffective
Horticultural oils, acephate, azadirachtin, afidopyropen, chlorantraniliprole, cyantraniliprole, Substugae strain PRAA4-1, Burkholderia spp. strain A396, and flupyradifurone have demonstrated very limited or no efficacy against the crapemyrtle bark scale at manufacturer recommended rates, applied twice early in the season. Specific circumstances, changes in timing, or tank mixing with other products may increase efficacy of the above mentioned active ingredients.