In Vermont, researchers have intentionally exposed thousands of trees to Dutch elm disease during the summer. The U.S. Forest Service and the Nature Conservancy are conducting this experiment to test if a new generation of elms, bred from disease-resistant survivors, could potentially resist the fungus transmitted by bark beetles. This fungus has been devastating elm populations in the U.S. and Canada for many years. The ultimate aim is to restore areas that were once abundant with tall elms, adorning city streets and flourishing along riverbanks.
Gus Goodwin from The Nature Conservancy expressed concern over the significant loss of trees due to Dutch elm disease over the years. Researchers are hopeful that the experiment in Vermont could lead to the development of elm strains resistant to the disease. Similar initiatives in Canada are also seeking solutions to combat the increasing threat of Dutch elm disease in new regions.
In Fredericton, known as the “City of Stately Elms,” the population of these trees drastically declined in the 1960s and 70s due to the disease, resulting in the loss of an estimated 10,000 trees, with only around 1,000 mature elms remaining. Anthony Taylor, a forest management professor at the University of New Brunswick, has observed the impact of the disease on surviving elms on his property.
Dutch elm disease spreads internally in trees, blocking water movement and leading to their eventual death within one to four years of infection. The fungus is further disseminated by bark beetles laying eggs in infected trees, creating new carriers that can transfer the disease to healthy trees. To control the disease, infected elms are promptly removed, a practice known as sanitization, which aims to eliminate the disease by removing affected plants. However, this approach may have inadvertently reduced the population of disease-tolerant trees.
The threat of Dutch elm disease has spread to new locations in recent years, with Edmonton and Saskatoon reporting increasing cases. Efforts are being made to remove infected trees promptly and prevent further spread by adhering to specific guidelines, such as refraining from pruning elm trees during certain periods.
Despite the challenges posed by Dutch elm disease, researchers are working diligently to enhance resilience against the disease. Programs like the Elm Recovery Project in Guelph have been ongoing for nearly three decades, focusing on crossbreeding and cloning disease-resistant trees. The long-term goal is to cultivate trees that can coexist with the disease, similar to elms in Europe, which have evolved to withstand Dutch elm disease. This breeding process takes time, involving multiple generations of trees, but could potentially lead to a more resilient elm population in North America.
