Updated: October 5, 2021
By Stanton Gill

Crapemyrtle Bark Scale First Confirmed in Maryland in 2020
For the last 25 years, crape myrtles have increased in Maryland nurseries and they are being used heavily in Maryland landscapes. Consequently, two pests, crapemyrtle aphid and crapemyrtle bark scale, have become serious pests of this plant. Crapemyrtle bark scale was first confirmed in Maryland by the Maryland Department of Agriculture in April 2020. The plant was growing in a landscape in Baltimore County. It was found in more Maryland landscapes throughout 2020, including in New Market (Frederick County) and Sykesville (Carroll County). The crape myrtles had copious amounts of honeydew and sooty mold coating the foliage. 

This new exotic scale pest, Acanthococcos (=Eriococcus) lagerstroemiae Kuwana (Hemiptera: Sternorrhyncha: Eriococcidae), commonly referred to as the crapemyrtle bark scale (CMBS), is a big deal and it is a major threat to the commercial viability of nursery and landscape plantings of crape myrtles. This pest was first found in the USA in Texas. The first sightings of CMBS were reported in McKinney, Texas in 2004 (Gu et al. 2014), and the scale has since spread to at least 11 states in the U.S, from New Mexico to Virginia (EDDMapS 2019). As of 2020, its range has expanded to Maryland and the District of Columbia. 

Life Cycle

Scale insects in the genus Acanthococcus are typically mobile as the first instars (crawlers), but become sessile within hours (Miller 1991). Subsequently, a white felt sac is produced to cover the bodies of 2nd instar males and adult females (Miller 1991), making them less vulnerable to contact insecticides (Muegge and Merchant 2000). As a result, knowing the times of peak crawler activity is critical for effective management of this pest with contact insecticides. More information is needed on its life cycle, but crawlers were still active in late August 2020. 

In China, crapemyrtle bark scale is reported to have 3 to 4 overlapping generations per year (Luo et al. 2000, He et al. 2008, Ma 2011). Multiple peaks of crawler activity seen in Texas and Arkansas suggest that CMBS has two or more overlapping generations per year, and possibly up to four generations as previously reported. Erfan Vafaie, Texas A&M, reports crawlers early in the spring. Vafaie found dormant rate oils of 2 -3 % will kill overwintering stages. 
Erfan reports crawlers in Texas and Arkansas starting in late winter and continuing into May. He said crawlers were reported later in the season indicating multiple generations per season. With crawlers crawlers and eggs in late August in Maryland, it looks like there are multiple generations of this pest occurring here as well.

This scale can reportedly infest 17 plant genera in 13 families, including economically important crops such as pomegranate (Punica granatum L.) (Ma 2011), soybean (Glycine max (L.) Merr.) and apple (Malus domestica Borkh) (Hua 2000). Crapemyrtle bark scale was recently confirmed (unpublished data, Allen Szalanski, University of AR) on Callicarpa sp. (beautyberry) in Texarkana, TX, Dallas, TX, and Shreveport, LA, and on Hypericum kalmianum L. (St. Johnswort) in Virginia (Schultz and Szalanski 2019).

With so many crape myrtles planted in this area, be on the look outlook for this scale. Again, the primary host is crape myrtle, but with all of the planting of apple trees, we need to make sure this scale does not start showing up on apples. Soybean is not a primary host, but it has been reported to feed on the plant. 

The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied. Read labels carefully before applying any pesticides.

Literature cited

Gu, M., M. Merchant, J. Robbins and J. Hopkins. 2014. Crape myrtle bark scale: A new exotic pest., EHT-049 3/14. The Texas A&M University System, Texas A&M AgriLife Extension Service.

He, D., J. Cheng, H. Zhao and S.-S. Chen. 2008. Biological characteristic and control efficacy of Eriococcus lagerstroemiae. Chinese Bull. Entomol. 5: 34.

Luo, Q., X. Xie, L. Zhou, S. Wang and Z. Xu. 2000. A study on the dynamics and biological characteristics of Eriococcus lagerostroemiae Kuwana population in Guiyang. Acta Entomol. Sin. 43: 35–41.

Ma, J. H. 2011. Occurrence and biological characteristics of Eriococcus lagerostroemiae Kuwana in Panxi District. South China Fruits. 5: 3.

Miller, D. R. 1991. The scales, scale insects or coccoids, p. 90–107. In: Stehr, F.W. (ed.), Immature Insects, Vol. 2. Kendall/Hunt, Dubuque, IO

Muegge, M. A. and M. E. Merchant. 2000. Scale insects on ornamental plants. Texas A&M AgriLife Ext. 1–8.

Vafaie, E.. 2020. M. Merchant, C Xiaoya, J. Hopkins, J. Robbins, Y. Chen, and M. Gu. Seasonal Population Patterns of a New Scale Pest, Acanthococcus lagerstroemiae Kuwana (Hemiptera: Sternorrhynca: Eriococcidae), of Crapemyrtles in Texas, Louisiana, and Arkansas. J. Environ. Hort. 38: 8–14.