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) incited by Erysiphe elevata (Burr.) U. Braun & S. Takam and feeding by catalpa sphinx larvae (CSL), Ceratomia catalpae (Boisduval). PM screening was conducted on plants grown in a lathhouse (50% shade) in 2004 and a gravel pad (100% sun) in 2005. The PM causal organism was identified as E. 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 year. North American Catalpa in sect. Catalpa, Chilopsis, and ×Chitalpa taxa were all moderately 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 transmission of partial resistance to PM. No differences in survival or growth were found in a no-choice feeding study with CSL reared on taxa from Chilopsis, ×Chitalpa, or either section of Catalpa. Future breeding of ×Chitalpa can use sources of PM resistance identified in this study, but a source of resistance to CSL was not found.
Susceptibility of Catalpa, Chilopsis, and Hybrids to Powdery Mildew and Catalpa Sphinx Larvae
