On the lookout for fungus that kills oak trees
It’s called watchful waiting. Being prepared.
There is a fungal disease — oak wilt — that can quickly kill oak trees, especially red oaks. White oaks, the state tree, seem to survive better. Beetles spread it. Oaks spread it, root to root.
New York found it on Long island and in Brooklyn in 2016, right on Connecticut’s doorstep. It’s also cropped up father to the west and north in New York. State officials there moved quickly to quarantine the counties where the fungus infected the trees and prevented people from shipping firewood elsewhere.
It isn’t in Connecticut. But Robert Marra, a forest pathologist with the Connecticut Agricultural Experiment
Station, wants people in the state — tree wardens, arborists, private landowners, the staff of the state Department of Energy and Environmental Protection — to be on the lookout.
And, he said, it might also be wise to think about how to deal with it if it does arrive. Recent human experience with the coronavirus points us in that direction.
“Now is the time to have a protocol in place,” Marra said. This is because oaks in general are one of the dominant trees in the state forest — the tree that feeds the forest family with its acorns, that’s prized for its timber, that can live for centuries, nobly shading its surroundings. It creates a landscape.
For that reason, people consider oak wilt a curse they can live without.
“I’ve never seen it,” said Sean McNamara, owner of Redding Nursery. “Hopefully, I never will.”
“Let’s hope it never gets here,” said Bruce Bennet, Kent’s tree warden.
Rolf Brandt, Bethel’s tree warden, said that in his years of tree work in Connecticut and in New York’s Westchester County, he never crossed paths with oak wilt. But it’s on his radar screen.
“It’s another thing to look out for,” Brandt said.
Chris Martin, state forester with the Department of Energy and Environmental Protection, said the DEEP and the agricultural experiment station have tried to get the word out about oak wilt and people are paying attention.
“We’re lucky in Connecticut,” he said. “We’ve got a very tight community, between the DEEP, the experiment station, the tree wardens, the arborists. That doesn’t occur in other states.”
Oak wilt is caused by a fungus — Bretziella fagacearum. No one knows where it came from. It was found first in Wisconsin in 1944 and has spread throughout the Midwest down to Texas, and east to Pennsylvania and New York. It’s killed tens of thousands of oaks.
When it infects a tree, the fungus grows in the tree’s outer sapwood, cutting off the flow of water and nutrients from roots to branches — the tree’s lifeblood.
As a result, an infected tree’s leaves will turn dull green or brown out of season, with the edges of the leaf becoming discolored while the center of the leaf stays green. Foliage first wilts at the top of the tree, then moves downward, causing leaves to drop prematurely.
The fungus grows into a thick black mat under a tree’s bark that can cause the bark to crack. The fungus also emits a juicy smell that attracts insects. They fly away with fungal spores on their body to infect other trees.
Furthermore, oaks connect tree-to-tree underground via their network of roots. The fungus travels along that root system, infecting trees as it goes along.
McNamara said the Dutch elm disease — another fungal blight — exploited the same root system to ruin the state’s urban landscape in the first half of the 20th century.
“It would go right down a street, killing elms,” he said.
Luckily, oak wilt doesn’t move quickly — unlike an insect blight like that caused by the emerald ash borer. That’s spread through the state in a few years, killing thousands of ashes in its wake.
Martin said oak wilt would also be easy to spot.
“You’d have one brown oak, surrounded by green,” he said.
In states where oak wilt occurs, arborists cut down the tree, and quarantine firewood sales. Marra of the experiment station said they also use trenching machines to dig around the perimeter of an infected tree to break the root connections.
Marra would like Connecticut to prepare now for the possible arrival of oak wilt. If it shows up, he said, the state could act more quickly to check it. Again, think COVID-19. “The US Forest Service doesn’t manage oak wilt,” he said.