Dutch Elm Disease in Winnipeg

Winnipeg, Manitoba, holds the largest surviving urban American elm (Ulmus americana) canopy in the world — an estimated 200,000 to 230,000 mature trees as of the 2010s. The preservation of this canopy in a city where Dutch Elm Disease has been present for decades is the result of a sustained, well-funded, and continuously operating municipal management program that began in 1975.

The Winnipeg elm canopy

Winnipeg's American elm population dates from the early 20th century, when the city planted American elms as the dominant street tree across most residential neighborhoods. The cool continental climate, well-drained prairie soils, and favorable urban conditions produced exceptional growth, and by mid-century the city's "cathedral" elm boulevards were among the most striking in North America.

Notable elm-canopied features include Wellington Crescent, the Wolseley neighborhood (often called "the granola belt" partly for its tree cover), and Armstrong's Point. Wellington Crescent in particular is widely regarded as one of the most beautiful elm-lined streets in North America.

DED arrival and response

Dutch Elm Disease was first detected in Winnipeg in 1975. The city responded immediately with an aggressive municipal program designed around three core elements:

Active surveillance — annual visual inspections of every mature elm in the city

Rapid sanitation — confirmed-DED trees are removed within weeks of diagnosis to eliminate beetle breeding sites

Beetle vector management — basal spray treatments with chlorpyrifos in spring to suppress emerging adult elm bark beetles

The program has operated continuously since 1975 with sustained municipal funding.

Why Winnipeg has succeeded

Several factors combined to make Winnipeg's preservation possible where other cities lost their canopies:

Cold climate: Winnipeg's long cold winters limit elm bark beetle (Hylurgopinus rufipes — the native species being the principal vector) population growth and the number of beetle generations per year

Geographic isolation: The city is surrounded by prairie with limited natural elm reservoirs, slowing the rate of new infection from outside the city

Early and sustained funding: The program was established at the start of the local outbreak and has retained municipal budget commitment for nearly five decades

Public participation: Strong public buy-in on yard tree reporting and firewood-movement restrictions

Provincial support: The Manitoba Dutch Elm Disease program provides surveillance and enforcement at the provincial level beyond city limits

Current status

Annual DED losses in Winnipeg typically run at 1,500–4,000 trees per year, depending on weather and beetle pressure — a small fraction of the mature population. The program's annual cost has been reported in the range of CAD $3 million.

The city actively plants resistant elm cultivars including 'Brandon' (Manitoba's regional selection), 'Discovery', and Prairie Expedition™ for replacement and gradual diversification.

International significance

Winnipeg's program is widely cited as a model for sustained municipal forest disease management. Researchers and forestry professionals from around the world visit the city to study both the canopy itself and the management program that preserves it.

Related pages

Dutch Elm Disease in Canada

Dutch Elm Disease in Minneapolis — comparable cold-climate program

American Elm (Ulmus americana)

Treatment & Management

References

Westwood, A. R. (1991). "A cost-benefit analysis of Manitoba's integrated Dutch elm disease management program 1975–1990." Proceedings of the Entomological Society of Manitoba, 47, 44–59.

Hubbes, M. (1999). "The American elm and Dutch elm disease." The Forestry Chronicle, 75(2), 265–273.

City of Winnipeg. Urban Forestry Branch annual reports.

Government of Manitoba. Dutch Elm Disease management program publications.