Stigmina pallida(Ellis & Everhart) M. B. Ellis incited a bark disease of apple characterized by cankers and discoloration of underlying wood of 1- and 2-year-old shoots. It differed in spore size and cultural characteristics fromS. negundinis(Berk. & Curt.) M. B. Ellis, a pathogen of box elder with which it had been considered to be cospecific.S. pallidahad larger spores (36–44–50 × 14–17–20 μ) than those ofS. negundinis(30–36–40 × 11–15–19 μ) and grew in agar culture at a slower rate over a narrower range of temperature.S. pallidawas pathogenic to apple and smooth sumac but not to box elder, whileS. negundiniswas pathogenic to box elder and smooth sumac but not to apple.