Crapemyrtle Bark Scale
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Management

Mechanical

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.

Biological

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.

Ants and crapemyrtle bark scale
Role that ants plant in promotion or suppression of crapemyrtle bark scale is not yet understood. Ants may be tending the scale for honeydew or consuming them for protein.
Ladybeetle eggs
Ladybeetle eggs often laid in clusters. Can be found on leaves or branches. Photo by Erfan Vafaie.
Harmonia axyridis larva
Multicolor Asian Ladybeetle larva feeding on crapemyrtle bark scale. Photo by Erfan Vafaie.
Chilocorus cacti
Chilocorus cacti having a mating party. Photo by Erfan Vafaie.
Ladybeetle pupa
Ladybeetle pupa; developmental stage from larva to adult. Photo by Erfan Vafaie.
Hyperaspis lateralis
Hyperaspis lateralis ladybeetle adult. Photo by Dr. Mike Merchant
Chilocorus cacti L.
Chilocorus cacti ladybeetle adult. Photo by Dr. Mike Merchant.
Scymnus or Hyperaspis
Scymnus or Hyperaspis larva, a type of ladybeetle. Photo by Dr. Mike Merchant.

Chemical

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.

Systemic

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.

Contact insecticides

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.

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