Dothiorella ulmi
Hosts
Elm
Distribution and Disease Cycle
Dothiorella wilt, also called Native elm wilt, caused by the fungal pathogen Dothiorella ulmi, infects elm species, producing symptoms very similar and frequently confused with those of Verticillium wilt or Dutch elm disease. The fungus overwinters in infected tissue, exuding spores in spring that are dispersed by wind, rain or insects. Infection occurs through wounds in leaves or young shoots, spreading to other plant parts through the vascular system. While this disease may progress more slowly than other wilt diseases, it will eventually be fatal as well.
Photo credit: City of Saskatoon
Symptoms and Signs
Dothiorella wilt infections result in wilting, curling and yellowing of foliage, premature defoliation and branch dieback, or canker formation on small branches. Infection causes brown streaking of internal tissue often before external symptoms appear. Because symptoms are very similar to other wilt diseases, accurate diagnosis can only occur following lab incubation and identification.
If practical, prune infected branches several feet below the last visible vascular discolouration, burning or burying infected branches. Repeated pruning may be required to adequately control this disease, although in severe infections eventual tree removal may be required. There are no chemical controls for Dothiorella wilt.
Control
If practical, prune infected branches several feet below the last visible vascular discolouration, burning or burying infected branches. Repeated pruning may be required to adequately control this disease, although in severe infections eventual tree removal may be required. There are no chemical controls for Dothiorella wilt.