Susceptibility of Crape Myrtles to Cercospora Leaf Spot in Georgia

Lagerstroemia (crape myrtle) is a genus of horticulturally important shrub or small flowering trees in landscapes across the southeast United States. Crape myrtles are impacted by the disease Cercospora leaf spot ( Pseudocercospora lythracearum ), which causes defoliation and reduces the value of affected plants in the nursery. Crape myrtle cultivars were rated over 6 months from June to November for Cercospora leaf spot incidence in 2021 and 2022 in Blairsville [US Department of Agriculture (USDA) zone 7b] and Watkinsville (USDA zone 8a), Georgia. Differences in disease development were noted between years. The cultivars most resistant to Cercospora leaf spot are Apalachee, Muskogee, Natchez, and Miami. ‘Ozark Spring’, ‘Victor’, ‘Dynamite’, and ‘Pink Velour’ had the greatest level of leaf spotting and premature defoliation. Lagerstroemia indica × fauriei hybrids were correlated with higher resistance to Cercospora leaf spot than L. indica . Lagerstroemia limii × indica hybrids demonstrated high susceptibility to Cercospora leaf spot. Hybrids of dark-foliage L. indica and L. subcostata were more resistant than dark-foliage L. indica plants. Resistance to Cercospora leaf spot was inconsistent among species, with some populations having individuals with very high and very low resistance. Hybridization of L. indica with L. fauriei and L. subcostata yields the highest likelihood of creating a crape myrtle resistant to Cercospora leaf spot.