By: Mengmeng Gu
Crapemyrtle bark scale (Acanthococcus lagerstroemiae) has been confirmed in all the Southeastern U.S. except for Florida. In its native range in East Asia, CMBS is a serious threat to crapemyrtles, persimmons, and pomegranate plants. In the U.S., it is an emerging pest that threatens crapemyrtle production and landscape use. This is a matter of concern because crapemyrtle is the highest selling flowering tree—5 million plants with a combined value of $67M were sold in 2014.
Currently, CMBS in the U.S. is only reported on crapemyrtles, but the spread of CMBS (confirmed by molecular identification) to native American beautyberry plants in Texarkana, TX and Shreveport, LA is alarming. This finding brings to 14 the number of economically and ecologically important plant families reported as host plants in the CMBS regions of origin (Table 1).
Among the documented plants infested by CMBS, other economically important crops include boxwood, soybean, fig, myrtle, cleyera, apple, and brambles, such as blackberry, raspberry, dewberry, juneberry etc. Since Chinese hackberry is identified as a host plant, this raises concern that the native hackberry—widely established in common crapemyrtle growing regions—may be a possible target species.
Lagerstroemia indica and L. fauriei cultivars are the most commonly grown crapemyrtle cultivars. In addition to 29 such cultivars, infestation of CMBS has been found on 4 crapemyrtle species (Lagerstroemia limii, L. speciosa, L. subcostata, and L. guilinensis) (Table 2). It’s reasonable to predict that none of these latter common cultivars or crapemyrtle species are immune to CMBS infestation.
CMBS may affect the following five beautyberry species (Callicarpa americana, C. formosana, C. ruebella, C. mexicana and C. dichotoma). It may also affect pomegranate, henna, heimia, and winged loosestrife, which has been confirmed under controlled environment. American beautyberry is native in all Southeastern states from Texas to Virginia (Fig. 3), which almost overlap with the CMBS-confirmed states. Natural CMBS infestations of American beautyberry have been found in landscapes in Texas and Louisiana. California produces the most pomegranate, but it is also grown in many states in the south (Fig. 4). Heimia is native in Texas (Fig. 5). Winged loosestrife is native in all states east of Rocky Mountains (Fig. 6). These plants, along with many other documented alternative hosts, such as privet, may provide a continuum for spreading CMBS infestation and may cause significant impact on native ecosystems in the Southeast.
Although CMBS is rarely kills plants, the persistent sooty mold it causes on branches and trunks of untreated plants may become unsightly. In extreme cases, the result can be plant romoval from landscapes and a decline in crapemyrtle sales and planting. Crapemyrtles are an important pollen (major protein source for bees) provider during the summer, when flowers from other plants with pollen are relatively scarce.
Crapemyrtle bark scale was listed as a key management arthropod and one of the top 9 pests reported in the past two years by the Greenhouse Grower magazine. In the most recent Pest Management Strategic Plan for Container and Field-Produced Nursery Crops in FL, GA, KY, NC, SC, TN, and VA: Revision 2015, it was noted that “no biological control of the crapemyrtle bark scale is known.” However, we have found that several lady beetle species and green lacewing larvae prey on CMBS. There is no report of CMBS in California currently, but the California Department of Food and Agriculture has rated CMBS as a 14 on a scale of 1 to 15 with 15 being highest in its pest rating proposal. It is “likely to establish a widespread distribution in California;” has “moderate host range,” has “both high reproduction and dispersal potential;” and “could cause both economic and environmental impacts.”
Many exotic pests that appear benign, not too harmful, or even useful at first glance are becoming invasive and causing significant economic and environmental impacts—CMBS should be taken very seriously.
For life cycle and management of CMBS, please see Texas A&M AgriLife Extension Service publication EHT-049: Crape Myrtle Bark Scale: A New Exotic Pest available at www. agrilifebookstore.org.
Mentioned species common and scientific names
- American beautyberry – Callicarpa americana
- Apple – M. pumila
- Boxwood – Buxus
- Brambles, such as blackberry, raspberry, dewberry, juneberry etc. – Rubus
- Chinese hackberry – C. sinensis
- Cleyera – T. japonica
- Crapemyrtle – Lagerstroemia spp.
- Fig – F. carica
- Henna – Lawsonia inermis
- Heimia – Heimia salicifolia
- Myrtle – Myrtus
- Native hackberry – C. occidentalis
- Persimmon – Diospyros kaki
- Pomegranate – Punica granatum
- Privet – Ligustrum spp.
- Soybean – G. max
- Winged loosestrife – Lythrum alatum
Download a printer-friendly version of this publication: Alternative Hosts of Crapemyrtle Bark Scale (pdf)
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