Crapemyrtle’s reputation as a low‑maintenance tree is fading, as invasive insects and fungal diseases increasingly damage them. A new guide in the Journal of Integrated Pest Management details various arthropod pests and diseases affecting crapemyrtle and outlines integrated management strategies for preserving this popular ornamental. Here, blooms in shades of pink, red, and white illustrate the diversity and landscape value of this widely planted landscape tree. (Image courtesy of Kripa Dhakal, Ph.D.)

By Kripa Dhakal, Ph.D.

Karla M. Addesso, Ph.D.

Madhav Parajuli, Ph.D.

Kripa Dhakal, Ph.D.

Crapemyrtle (Lagerstroemia spp.) is one of the most recognizable and widely planted ornamental landscape trees in the United States. Valued for its vibrant summer blooms, attractive exfoliating bark, heat and drought tolerance, and adaptability to urban environments, crapemyrtle has long been considered a low-maintenance landscape plant. However, that reputation is increasingly threatened by pests and diseases.

In an article published in March in the Journal of Integrated Pest Management, my colleagues Madhav Parajuli, Ph.D., Karla M. Addesso, Ph.D., and I synthesize current knowledge on the most economically important arthropod pests and diseases affecting crapemyrtle and outline integrated management strategies.

A Valuable But Increasingly Vulnerable Ornamental

Introduced to the United States in the late 1700s, crapemyrtle is now a dominant ornamental tree in the Southern United States, generating an annual wholesale value exceeding $65 million. Breeding between Lagerstroemia indica and Lagerstroemia fauriei has produced more than 200 hybrid cultivars with diverse plant sizes, flower colors, and varying levels of disease resistance. However, increasing global trade, climate variability, and dense nursery plantings have increased pest and disease issues. Crapemyrtle is affected by invasive scale insects, sap-feeding aphids, foliar-feeding beetles, and foliar diseases, which significantly reduce aesthetic value and marketability.

The Insects Causing the Most Trouble

Crapemyrtle’s reputation as a low‑maintenance tree is fading, as invasive insects such as the crapemyrtle aphid (Sarucallis kahawaluokalani, adult at left, nymphs at right) and fungal diseases increasingly damage them. Aphid feeding leads to the development of black sooty mold that covers foliage and interferes with photosynthesis. Severe infestations may result in leaf yellowing, premature leaf drop, and reduced flowering. Photos by Alfred Daniel Johnson, Tennessee State University, originally published in Dhakal et al. 2026, Journal of Integrated Pest Management)

The crapemyrtle aphid (Sarucallis kahawaluokalani) has long been recognized as the most common pest of crapemyrtle in North America. This species is considered monophagous, feeding exclusively on crapemyrtle. These small, yellow-green insects feed on the undersides of leaves, withdrawing plant sap and producing large quantities of honeydew. Similar to bark scale infestations, aphid feeding leads to the development of black sooty mold that covers foliage and interferes with photosynthesis. Severe infestations may result in leaf yellowing, premature leaf drop, and reduced flowering.

Another economically significant pest is the invasive crapemyrtle bark scale (Acanthococcus lagerstroemiae). First detected in Texas in 2004, this pest has spread rapidly across multiple states. Unlike aphids, bark scale colonizes trunks and branches, forming white, felt-like coverings that cling tightly to the bark. They excrete honeydew during feeding that coats stems and promotes black sooty mold growth. Heavy infestations can cause branch dieback and reduce flower number. Economic analyses estimate that infestations may reduce plant market value by more than 50 percent.

Crapemyrtle’s reputation as a low‑maintenance tree is fading, as invasive insects such as crapemyrtle bark scale (Acanthococcus lagerstroemiae) and fungal diseases increasingly damage them. Bark scale colonizes trunks and branches, forming white, felt-like coverings that cling tightly to the bark. Here, at left a crapemyrtle branch is infested with crapemyrtle bark scale. Scale crawlers exude a pink or reddish residue when crushed, as shown at right. (Photos courtesy of Kripa Dhakal, Ph.D.)

The Japanese beetle (Popillia japonica) also contributes to seasonal damage in many eastern states. Adult beetles skeletonize leaves and feed on flowers during the summer. Although damage is primarily aesthetic, large aggregations can rapidly defoliate susceptible trees.

Major Diseases to Watch

Fungal diseases further complicate crapemyrtle management. Powdery mildew caused by the fungus Erysiphe lagerstroemiae appears as white or gray powdery growth on young leaves, stems, and flower buds. Infected foliage becomes distorted or stunted, leading to reduced bloom production. Warm days, cool nights, and high humidity favor disease development, particularly in dense plantings with poor air circulation.

Later in the growing season, cercospora leaf spot, caused by the fungus Pseudocercospora lythracearum, has emerged as another economically important disease of crapemyrtle. Symptoms typically begin in late summer as small tan to brown spots with yellow halos on lower leaves and gradually progress upward. Severe infestations lead to premature defoliation, diminishing landscape appeal late in the season.

Integrated Pest Management: A Multilayered Approach

Effective management begins with host-plant resistance through careful cultivar selection. Higher aphid populations have been reported on hybrid cultivars of Lagerstroemia indica × Lagerstroemia fauriei than on cultivars of L. indica. In contrast, many hybrid cultivars developed with L. fauriei exhibit improved resistance to powdery mildew and cercospora leaf spot. Choosing resistant cultivars can substantially reduce insecticide and fungicide dependence and long-term maintenance costs.

Cultural practices further strengthen plant health and reduce pest and disease pressure. Avoiding excessive nitrogen fertilization can also prevent lush vegetative growth that favors aphid proliferation and disease outbreaks. Pruning and proper disposal of heavily infested branches can reduce localized pest populations. Proper plant spacing improves air circulation and reduces humidity within the canopy, which helps to reduce pest and pathogen pressure. Removing fallen leaves at the end of the season helps reduce overwintering fungal mycelium.

Crapemyrtle’s reputation as a low‑maintenance tree is fading, as invasive insects and fungal diseases increasingly damage them. Among options for managing arthropod pests are natural enemies such as lady beetles (adult, larva, and pupa shown here, left to right). These beneficial insects actively prey on aphids, helping to suppress pest populations and maintain plant health in crapemyrtle landscapes. (Photo courtesy of Kripa Dhakal, Ph.D.)

Biological control plays an important supporting role. Lady beetles, lacewings, and other natural enemies frequently suppress aphid populations in landscape settings. Conserving these beneficial insects by minimizing broad-spectrum insecticide use promotes natural regulation. Researchers are also evaluating predators and parasitoids that may contribute to long-term suppression of aphid and bark scale populations.

When pest pressure exceeds economic or aesthetic thresholds, targeted chemical control may be necessary. Soil-applied systemic insecticides have proven effective against bark scale and aphids. Contact insecticides must be properly timed, particularly during crawler (first-instar nymph) emergence, as this is the only stage during which they are mobile and highly vulnerable to contact sprays. Preventive fungicide applications beginning shortly after bud break may be warranted in high-pressure nursery settings, especially when susceptible cultivars are grown.

A Clear Takeaway: Integration is Essential

Across all these challenges, one theme is clear: Sustainable management depends on integration rather than reliance on a single tactic. Resistant cultivars, proper site selection, routine monitoring, sanitation, conservation of natural enemies, and judicious use of insecticides collectively form the foundation of integrated pest management (IPM) in crapemyrtle production and landscapes. As climate variability and global trade continue to influence pest and disease dynamics, research-driven strategies and informed plant selection will be essential to preserving the health and ornamental value of this iconic landscape tree.

Kripa Dhakal, Ph.D., is a postdoctoral researcher in the Department of Agriculture Science & Engineering at Tennessee State University’s Otis L. Floyd Nursery Research Center in McMinnville, Tennessee. Email: [email protected].