Forestry professors at Université Laval don’t have to go far to show their students a case study of tree pathology and how an aggressive management program can help save a species: “We just have to walk outside,” says Louis Bernier, a professor with Laval’s department of forestry and wood sciences and a specialist in the genetics of tree-killing fungi.
That’s because the Laval campus is home to a large population of mature American elms. That makes it, together with surrounding Quebec City, one of the last bastions of what was once the most prized species of indigenous trees on the North American urban landscape.
Planted in the 1950s, just before a second deadly wave of Dutch elm disease wiped out an estimated 90 percent of the umbrella-canopied trees across the continent, Laval’s elms are today part of a municipal protection program that is designed – with help from the school’s professors and students – to keep them healthy and alive for future generations.
Begun in the early 1980s, the program initially focused on the removal of infected elms on public land, including city streets and parks like the Plains of Abraham. Caused by a fungus that is spread from tree to tree by elm-loving beetles – much like bees carrying pollen between flowers – Dutch elm disease is in essence a vascular illness that affects the host’s ability to distribute water, resulting in curled leaves, dry branches and, eventually, death.
Five years ago, Laval forestry professor Guy Bussières proposed a more aggressive prevention system: the deployment of traps designed to catch the two kinds of elm-loving insects that are capable of carrying the fungus. “The idea was to get an idea of how prevalent they were in the region,” says Dr. Bussières, the city’s go-to elm expert. “Unfortunately, the results showed that one kind was doing very well.”
During the summer months, eight student inspectors crisscross the city to inspect the estimated 20,000 elms on public and private lands. “We can’t usually save infected trees,” says Dr. Bussières, who has developed a new biological treatment to prevent the disease that he hopes to test on some elms this summer. “Monitoring is our best weapon for now, and it’s nice that forestry students are able to help.”
Dr. Bernier agrees. In addition to helping both the university and the city protect their existing populations of elms, he says, students are learning a valuable lesson about the importance of tree management in urban areas. “We’re lucky to still have elms,” says Dr. Bernier, who credits both Quebec City’s northern location and the city’s protection program for their continued existence.