Scientists test disease-resistant elm seedlings to revive Canadian urban canopies

In Vermont, researchers from the U.S. Forest Service and The Nature Conservancy have begun a large-scale trial, injecting thousands of elm seedlings with Dutch elm disease spores to pinpoint individuals that can survive the pathogen. The experiment builds on decades of work by Canadian groups, including the Elm Recovery Project at the University of Guelph arboretum, which maintains a gene bank of over a hundred disease-exposed trees and is now preparing to evaluate seedling performance.

The disease, spread by bark beetles and root contact, has decimated elms across North America, wiping out an estimated 10,000 trees in Fredericton and leaving only about 1,000 mature specimens. Municipalities such as Edmonton (17 infected trees) and Saskatoon (23 cases) have shifted to active management, removing infected trees promptly and urging residents to observe pruning bans. Scientists hope that resistant cultivars will allow elms to coexist with the fungus, restoring shade, storm-water benefits, and biodiversity to urban landscapes threatened by climate change. If successful, the breeding program could accelerate a co-evolution process that would otherwise take centuries.