U.S. Forest Service injects 6,000 young elms with Dutch elm disease spores

Survivors to grow in seed orchard for 15 years before restoration

The U.S. Forest Service and The Nature Conservancy Vermont are spending this summer putting American elms through a deliberate test: injecting 6,000 young trees with the fungus that has already killed tens of millions of their forebears. The experiment, based near Montpelier, Vermont, is the first stage of a long-running effort to identify disease-tolerant specimens and, eventually, to restore towering elms to the forests, riverbanks, and backyards where they once stood.

The young elms under inoculation descend from a small group of disease-surviving trees scattered across the Northeast that have resisted Dutch elm disease since the pathogen first arrived in the United States less than a century ago. By exposing those seedlings to the fungus and tracking which survive, the researchers aim to identify the most resistant specimens and rebuild the genetic diversity that the epidemic has eroded over decades.

Wilson, a research ecologist with the U.S. Forest Service who is leading the project, described the next stage in similarly long-term terms. Trees that survive the experimental inoculation will be planted in a fenced seed orchard and grown for roughly 15 years — long enough, she said, to reach reproductive maturity and produce seeds that can be deployed for restoration work.

“We will put those newly propagated trees into a seed orchard, basically just a big fenced area, will grow and love those trees for about 15 or so years, at which point they should produce seeds, and that seed can be used for restoration,” Wilson said.

Dutch elm disease is caused by a fungus spread from tree to tree by bark beetles. Once inside an elm, the pathogen disrupts the tree’s ability to move water through its vascular system, effectively starving it. The fungus arrived in the United States less than a century ago and spread rapidly through elm populations, leaving towering specimens — elms taller than 70 feet, or 21 meters — far less common in New England than they were generations ago.

The Vermont effort sits within a broader national push against forest pests and diseases, which researchers describe as threats to longstanding industries such as logging and to some of the nation’s most fragile ecosystems. The Nature Conservancy Vermont is partnering with the Forest Service on the elm project; the specifics of how the surviving trees’ seeds will eventually be deployed will depend on which specimens prove most resistant.