Reaction of 43 cultivars in three crapemyrtle taxa (Lagerstroemia indica, L. indica x fauriei and L. fauriei) to powdery mildew (Erysiphe lagerstroemia) and Cercospora leaf spot (Cercospora lythracearum) was evaluated for three years in a simulated landscape planting in Auburn, AL. Overall, the incidence of powdery mildew was lower on L. indica x fauriei and L. fauriei than on L. indica. In two of three years, Cercospora leaf spot severity was similar among all cultivars of L. indica and L. indica x fauriei, while the single selection of L. fauriei ‘Fantasy’ proved highly resistant to this disease. Selected cultivars in each crapemyrtle taxa were resistant to one or both diseases. Over the three-year evaluation period, hybrid cultivars ‘Tuscarora’, ‘Tuskegee’, and ‘Tonto’, as well as L. fauriei ‘Fantasy’ were largely free of powdery mildew and suffered little damage from Cercospora leaf spot. Cultivars suffering light injury to the foliage along with little noticeable defoliation from either disease were L. indica x fauriei ‘Basham's Party Pink’, ‘Apalachee’, ‘Caddo’ as well as L. indica ‘Cherokee’ and ‘Glendora White’. Lagerstroemia indica ‘Carolina Beauty’, ‘Wonderful White’, ‘Raspberry Sundae’, ‘Powhatan’, ‘Peppermint Lace’, ‘Majestic Beauty’, and ‘Orbin Adkins’ were susceptible to both powdery mildew and Cercospora leaf spot. The mildew-resistant cultivars ‘Acoma’, ‘Near East’, ‘Yuma’, ‘Souix’, ‘Hopi’, and ‘Comanche’ suffered extensive spotting of the leaves, which extended well into the mid-canopy, along with heavy leaf shed due to Cercospora leaf spot. Cultivars which are susceptible to one or both diseases would be poor choices in low maintenance commercial or residential landscapes.
2Professor of Plant Pathology and Extension Specialist.
3Professor of Horticulture, Department of Horticulture.
4Associate Professor of Horticulture, Department of Horticulture.
5Research Technician, Department of Horticulture.