Decoding cultivar susceptibility: Aphid performance and plant defense traits in crape myrtles

Crape myrtles (Lagerstroemia spp.) are among the most economically important ornamental plants in the southeastern United States, but their value is increasingly threatened by infestations of the crape myrtle aphid (Tinocallis kahawaluokalani). Aphid feeding leads to chlorosis, leaf curling, and honeydew accumulation, which promotes unsightly sooty mold—significantly reducing the plants' aesthetic and commercial appeal. Notably, susceptibility to aphid damage varies among cultivars, yet the underlying mechanisms driving this variation remain poorly understood. This study investigated aphid performance—quantified through development rates and population growth—on seven widely cultivated Lagerstroemia cultivars. In parallel, we assessed a range of plant traits, including morphological features and chemical profiles, to identify potential factors contributing to cultivar-level resistance or susceptibility. Chemical analyses focused on nutritional and antinutritional compounds, including tannins, polyphenols, flavonoids, structural carbohydrates, and protein concentrations. By integrating aphid performance metrics with phytochemical and morphological data, this research aims to clarify the plant traits most strongly associated with CMA success. Preliminary findings suggest that both physical and chemical defenses may contribute to cultivar-specific resistance, offering a clearer framework for pest management decisions in nursery and landscape settings. Ultimately, this work will support the selection and cultivation of more resistant Lagerstroemia cultivars, reducing reliance on chemical insecticides and enhancing the sustainability of ornamental plant production systems.