 He specialized in research of rust fungi (Uredinales) — from 1887 to 1943 he was the author of 150 scientific papers on rusts.His extensive treatment of rust fungi in Engler and Prantl's "Die Natürlichen Pflanzenfamilien" was recognized as its definitive account for many years.In 1897 Paul Christoph Hennings named the genus "Dietelia" (family Pucciniosiraceae) in his honor.