A diverse collection of germplasm representing 24 taxa from Catalpa sect. Catalpa Paclt and sect. Macrocatalpa Grisebach, Chilopsis D. Don, and ×Chitalpa Elias & Wisura were screened for susceptibility to powdery mildew (PM), Erysiphe elevata (Burr.) U. Braun & S. Takam, and Catalpa sphinx larvae (CSL), Ceratomia catalpae (Boisduval), feeding. The PM screening was conducted in 2004–05, with plants grown in a lathhouse (50% shade) in 2004, and a gravel pad (100% full sun) in 2005. The PM causal organism was identified as Erysiphe elevata both years. Disease incidence and severity were recorded at 2-week intervals for 6 weeks and used to calculate area under the disease progress curves (AUDPC) for each taxon for each year. North American Catalpa in sect. Catalpa, Chilopsis, and ×Chitalpa taxa were all moderate to highly susceptible to PM. Chinese Catalpa in sect. Catalpa and West Indian species in sect. Macrocatalpa were resistant to PM. Hybrids between North American and Chinese Catalpa in sect. Catalpa varied in susceptibility, indicating inheritance of partial resistance to PM. A no-choice feeding study conducted with CSL in 2005 found no differences in survival or growth of larvae reared on taxa from Chilopsis, ×Chitalpa, or either section of Catalpa. Future breeding of ×Chitalpa can utilize two different sources of PM resistance, but a source for resistance to CSL was not identified.