Dutch elm disease pathogen transmission by the banded elm bark beetle S colytus schevyrewi

Summary Dutch Elm Disease ( DED ) is a vascular wilt disease of U lmus species (elms) incited in N orth A merica primarily by the exotic fungus O phiostoma novo‐ulmi . The pathogen is transmitted via root grafts and elm bark beetle vectors, including the native N orth A merican elm bark beetle, H ylurgopinus rufipes and the exotic smaller European elm bark beetle, S colytus multistriatus . The banded elm bark beetle, S colytus schevyrewi, is an exotic Asian bark beetle that is now apparently the dominant elm bark beetle in the R ocky M ountain region of the USA . It is not known if S . schevyrewi will have an equivalent vector competence or if management recommendations need to be updated. Thus the study objectives were to: (i) determine the type and size of wounds made by adult S . schevyrewi on branches of Ulmus americana and (ii) determine if adult S . schevyrewi can transfer the pathogen to American elms during maturation feeding. To determine the DED vectoring capability of S . schevyrewi , newly emerged adults were infested with spores of O phiostoma novo‐ulmi and then placed with either in‐vivo or in‐vitro branches of A merican elm trees. The inoculation of trees via feeding wounds was successful 30% of the time for in‐vivo trials and 33% for in‐vitro trials. Although the infection rate of DED has declined in Colorado over the past 10 years, the disease is still present in urban elms. While it appears that S . schevyrewi is another vector of the DED pathogens, it appears that S . schevyrewi is no more efficient than S . multistriatus . Thus, management programs that remove elm bark beetle breeding sites, rapidly remove DED ‐infected elms and include the planting of DED ‐resistant elms should continue to be effective management tactics.