Photo credit: Giovana Franco

The crape myrtle bark scale (CMBS), Acanthococcus lagerstroemiae, is a scale insect native to East Asia and feed mainly on crape myrtle (Lagerstroemiae sp.) and beautyberry (Callicarpa americana) trees. CMBS can colonize branches, tree trunks and inflorescences. Secretion of honey-dew leads to growth of black sooty mold in the branches.

Photo credit: EDD Maps

Distribution

CMBS is found in Louisiana, Arkansas, Oklahoma, Virginia, Tennessee, North Carolina, Mississippi, Alabama, New Mexico, and Georgia.

Photo credit: Zinan Wang

Identification and Life Cycle

Infestations of CMBS can be recognized by white dots along the tree. Under large infestation the branches have a blackish appearance. The first stage of CMBS, called crawler, is responsible for the short or long distance dispersal. Crawlers settle on a branch and will develop into nymph which will produce a waxy protection. Adults has sexual dimorphism which means that males are morphological different than females. Males turn in to pupae and then hatch as winged small insects, meanwhile the females remain as immotile scales. Once they mate, the females produce eggs that stay protected under a layer of wax until they hatch.

Life stages of the CMBS (a) Egg; (b) Nymph; (c) Pupa covered with white sac; (c-1) and (c-2) males like inside the cocoon; (d) Adult female; (e) Adult male; and (f) Female and the new eggs.

Issue

The scale can colonize different parts of the trees causing direct and indirect damage. Direct damage due to sap consumption which could lead to branch dieback, and indirect damage due to honeydew secretion which provides substrate to black sooty-mold growth. These damages results in an unpleasant appearance and less production of flowers.

Photo credit: Giovana Franco
Black sooty mold in Crape myrtle trees infested with CMBS

Control of Crape Myrtle Bark Scale

Chemical control

• CMBS is managed by soil-applied systemic neonicotinoids, and infested branches are being treated with acephate and imidacloprid. However, these pesticides could interfere with beneficial insects such as bees, ladybeetles and parasitoids.

Mechanical control

• Small infestations can me mechanically removed by washing the trunk, and trimming infested branches.

Biological control

• Natural enemies are commonly seen in infested trees in Louisiana. The most frequent are the ladybeetles: Chilocorus cacti, C. stigma and Hyperaspis bigeminata, and Harmonia axyridis.

Photo credit: Giovana Franco

Ladybeetles H. bigeminata adult and Chilocorus sp. larvae, respectively, in the field.

Photo credit: Zinan Wang

Larvae and adult of Hyperaspis bigeminata.

For more information about the crape myrtle bark scale and management options, please visit:

http://www.lsuagcenter.com/NR/rdonlyres/0C57CFE2-CAA2-444B-A1AB-DED45AFC5009/103115/Pub3440BugBizCrapeMyrtleBarkScale_FINAL.pdf

Additional Resources

EDDMapS. Early Detection & Distribution Mapping System. https://www.eddmaps.org/distribution/usstate.cfm?sub=80722 (accessed on 25 April 2018).

Gill, D. How to deal with scale insects. http://www.lsuagcenter.com/profiles/jmorgan/articles/page1520001364362 (accessed on 12 March 2018).

Kilpatrick, R., Owings, A., Pollet, D., and Ring, D. Crape Myrtle Bark Scale. http://www.lsuagcenter.com/MCMS/RelatedFiles/%7B84F4324A-45E7-4D09-8F2A-A51D127149F5%7D/Crape-Myrtle-Bark-Scale-Fact-Sheet.pdf (accessed on 5 March 2018).

Wang, Z., Chen, Yan; Diaz, R. The cactus lady beetle: a voracious predator of scale insects. http://entomology.lsu.edu/assets/thecactusladybeetle.pdf (accessed on 5 March 2018).

Wang, Z., Chen, Y., Knox, G. W., Ring, D., Diaz, R. (2015) Crape Myrtle Bark Scale. http://www.lsuagcenter.com/NR/rdonlyres/0C57CFE2-CAA2-444B-A1AB-DED45AFC5009/103115/Pub3440BugBizCrapeMyrtleBarkScale_FINAL.pdf (accessed on 10 May 2018).

Wang, Z., Chen, Y., Gu, M., Verdaie, E., Merchant, M., Diaz, R. (2016) Crapemyrtle Bark Scale: A New Threat for Crapemyrtles, a Popular Landscape Plant in the U.S. Insects, 7(4):78 doi: 10.3390/insects7040078

Author: Giovana Matos.

Instructor: Dr. Rodrigo Diaz, rdiaz@agcenter.lsu.edu