Crapemyrtle Bark Scale: Now in Maryland 2020

Crapemyrtle Bark Scale: Now in Maryland
                                                           2020

By: Stanton Gill, Extension Specialist in Entomology, University of Maryland Extension

In August 2020, I visited two sites with crape
myrtles that were showing copious amounts of
honeydew and sooty mold coating the foliage.
Crapemyrtle bark scale (CMBS) was accidently
introduced into these two landscape sites. One site
was in New Market (Frederick County), near Lake
Linganore, and the second site was in Sykesville
(Carroll County). For the last 25 years, crape
myrtles have increased in Maryland nurseries and
they are being used heavily in Maryland landscapes.

The site in New Market had one very heavily
infested crape myrtle and three other crape myrtle
plants with lower numbers present. It was rather
obvious that the one plant was likely the plant that Females of crapemyrtle bark scale were present on a crape
was installed with the scale present which was       myrtle sample from New Market, MD on August 24, 2020.
spreading to the adjacent plants. We examined
branch samples at the CMREC lab and found
many females that were loaded with eggs. We
contacted the nursery that sold the plants to the
owner. The crape myrtle had been shipped in from
a southern nursery supplier. The heavily infested
plant was destroyed the week of my visit, and the
other adjacent plants were treated with systemic
insecticides. Crawlers were active on samples from
both sites. With crawlers being present, you could
use Distance or Talus to control them if you catch
them now before they cover their body with white
wax.

This new exotic scale pest, Acanthococcos              A female was flipped over to reveal the eggs. This sample
(=Eriococcus) lagerstroemiae Kuwana (Hemiptera: was from New Market, MD on August 24, 2020.
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 have since spread to at least
11 states in the U.S, from New Mexico to Virginia (EDDMapS 2019). Since we have this scale in Maryland
now, we can say it is now in 12 states and the District of Columbia.

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. This pest is new in
Maryland, and we have not worked out the life
cycle in our state at this point. I know we are seeing
crawlers now in late August.

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      Crawlers are active on this sample
spring. Vafaie found dormant rate oils of 2 -3 % will
kill overwintering stages.

Erfan Vafaie, Entomologist at Texas A & M, has looked at the life
cycle in Texas and evaluated several control materials for dealing
with this felted scale. 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. Since we are seeing crawlers and eggs in late August
in Maryland, I would agree that we have multiple generations
of this pest occurring.

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).
                                                                       The stage commonly seen during the winter
Please be on the look outlook for this scale and let us know if and in Texas, but it has yet to be confirmed
where you find it active. Again, the primary host is crape myrtle, officially as the overwintering stage
but with all of the planting of apple trees in the Covid-19 rush for Photo: Erfan Vafaie, Texas A&M University
homeowners to install fruit trees we want 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.

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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.

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