A 200-year-old American elm tree stood condemned, finally succumbing, it seemed, to the disease that has killed off hundreds of thousands of other elms in Minnesota.

The tree, one of the few old elms left in the Twin Cities, towered over a small channel of Minneapolis' Lake of the Isles long before Minnesota was a state. Somehow it survived untreated as Dutch elm disease spread over the last 50 years from neighborhood to neighborhood. Its trunk, wide enough to walk through, bent into an oval as it grew and squeezed between a sidewalk and two-lane road built around it.

But, at last, foresters found Dutch elm disease — a fatal fungal infection spread by beetles — in the tree this fall. They planned to cut it down Oct. 1.

Then Kyla Wahlstrom stepped in.

Wahlstrom, who's lived in the neighborhood for 42 years, saw the spray-painted red stripe around the trunk — the telltale marking of a tree destined to be cut down — while walking her 11-month-old retriever. She had lost some of her own trees to the disease, but none that were this tall, this old or this remarkable.

Wahlstrom estimated that the elm, which has a circumference of 16 feet, was between 195 and 225 years old.

"Think of all the things it's seen and lived through," Wahlstrom said. "All the hard winters and droughts. It was here when Minnesota was just a territory."

Wahlstrom, a retired professor at the University of Minnesota, said she learned long ago not to take things at face value. If the tree was to be cut down, she wanted to know exactly why there was no other option.

She talked to the city foresters who found the disease, then to several other professionals and experts. She learned that while the disease is a certain death sentence when it makes it to a tree's roots or main trunk, the tree can survive if the infection is only within its branches.

Wahlstrom had the tree retested. Sure enough, the disease had not yet spread to the trunk.

Support grew in the neighborhood to save it.

Xandra Coe, who lives right next to the elm, offered to pay for regular pesticide treatments that will keep beetles and disease from coming back. City foresters approved the treatment plan and agreed to prune the infected branches.

They sprayed over the red stripe with black, unmarking it. The tree that has already survived so much will continue to live.

That's hopeful news to Ben Held and Ryan Murphy, researchers at the U who are working to breed elms resistant to the disease. They noted that the old ones that have fought off or survived Dutch elm disease this long are particularly important to keep around.

"It's pretty rare to find the large old ones," Murphy said. "Those are the ones that are giving us the biggest benefits."

Held and Murphy work with the U's Minnesota Invasive Terrestrial Plants and Pests Center to try to find out why some elms have proved to be more resistance to the disease. The hope is that by breeding them together over generations they'll be able to create strands of elm that can survive as long as the one Wahlstrom saved.

What made Dutch elm disease so devastating is how popular elms have always been. They grow fast and tall, are extremely durable and open up into large canopies providing great shade and fall colors. By the 1970s, when the disease made it to St. Paul, about 95% of the trees some cities planted in boulevards and rights of way were elm trees. In early 1970s, the seven-county metro area lost tens of thousands of elms a year. The peak of the spread was 1977, when the metro lost more than 190,000 elms. The entire state has lost an estimated 140 million trees to the disease.

Fortunately, elms grow fast enough that they have never been at risk of extinction. They still make up about 5% of the canopy on many boulevards in the state, Murphy said.

But the vast majority of those have grown up in the last few decades. Survivor elms that were around before the disease made it to Minnesota are few and far between, which is what makes them so valuable to researchers, Held said.

"The natural population appears to have that varying level of resistance," he said.

Neighbor Coe said the benefits of keeping old trees alive far outweigh the cost of the treatment, which can run a few hundred dollars a year depending on the size of the tree. She said she hopes more neighborhoods might keep an eye out for any old trees in public rights of way that could be saved with treatments.

Wahlstrom is happy to see neighborhood kids taking measuring tape and calculating the ages of other trees throughout the channel.

And she hopes the tree that was here long before anyone alive was around will remain long after she's gone. She keeps her favorite motto on her refrigerator — words that she tries to live by.

It says, "Act as though what I do makes a difference."

"That's what I tried to do," she said.

Greg Stanley • 612-673-4882