Susceptibility of Crape Myrtle, Lagerstroemia indica L., to the Crapemyrtle Aphid (Homoptera: Aphididae) in North Florida

Thirty seven cultivars of the crape myrtle, Lagerstroemia spp., were evaluated in a two year study in north Florida for susceptibility to the crapemyrtle aphid, Tinocallis kahawaluokalani (Kirkaldy). Numbers of crapemyrtle aphids per leaf were monitored each week from June to October in 1990 and 1991. Peak aphid numbers occurred in both years during the last week in July. Cultivars with L. fauriei parentage, and cultivars that are susceptible to or those with resistance to powdery mildew had significantly higher aphids per leaf than cultivars considered tolerant of powdery mildew. Aphid numbers were not related to flower color or leaf area, but tall and semi-dwarf cultivars had significantly more aphids than dwarf or medium-sized cultivars. Mean number (± SE) of aphids per leaf per sample date varied from a low of 6.2 ± 1.7 on ‘Centennial Spirit’ to 84.8 ± 19.1 on ‘Biloxi’.