'City of Stately Elms' working on a fix for Dutch elm disease

In an area once known for its canopy of elm trees, Dale Simpson presses a needle into a small, drilled hole in the crutch of a skinny white elm tree.

He is injecting it with spores that carry Dutch elm disease, which ravaged the elm tree population throughout North America.

Simpson, the manager of the National Tree Seed Centre in Fredericton, will inject 90 trees this spring and then watch closely over the next couple of months for signs of the disease. 

Simpson said he hopes within a couple of years there will be disease-resistant elm trees.

"That would provide two options: leave the ones that are tolerant to the disease to produce seed, or go back to these trees and collect cuttings and use those cuttings to produce stock that could be used for planting around the city or elsewhere," said Simpson.

"If the tree still survives, that's great. If it doesn't, then it doesn't have any inherent resistance or tolerance to the disease."

So far, Simpson has seen some of the young trees develop the disease, turning the leaves yellow and then black. But the disease seems to be contained to the injected branch. Other trees haven't shown any ill effects.

"Worst-case scenario, the whole tree will be dead. I haven't killed a whole tree yet," he said.

The trees are part of a project that began 15 years ago when the Atlantic Forestry Centre took cuttings from elm trees that Simpson calls "flukes."

These are elm trees that survived the ravages of the disease that was first spotted in the province in 1957. The cuttings were grafted onto seedlings, creating 150 new trees.

Dutch elm disease is carried by the native elm bark beetle. The beetles look for dying or dead trees, tunnel under the outer bark, breed and then carry the spores to healthy trees, thereby infecting them. 

The fungus can also travel root to root. 

Trying to control the disease has meant cutting down any elm trees that appear infected.

First spotted in 1961

The disease was first spotted in Fredericton in 1961 in just two trees, but by 1990, more than 13,000 trees were cut down to prevent its spread, according to a 1993 Natural Resources Canada report.

In 2006, the city reduced the area it policed to a more manageable area, removing about 150 trees a year, while at the same time planting Valley Forge elms, because they are "disease tolerant."

Unfortunately, they weren't weather tolerant, according to Neil Trebble, Fredericton's arboricultural foreman.

He said the Valley Forge trees' "structure wasn't great" and they tended to break apart in high winds.

More recently, the city has started planting Princeton elms, hoping they will fare better.

So what does it matter if Simpson's experiment provides local root stock?

"It matters considerably," says Neil Trebble.

"It would be amazing if we had a tree that was grown here in Fredericton that was disease resistant," because a tree used to the weather events in the area is much more likely to survive and thrive.