NEWS

Answer Man! Why are trees coming down at nature center?

Steve Pokin
SPOKIN@NEWS-LEADER.COM

Hey Answer Man! My husband and I have lived near the Springfield Nature Center for 33 years. My daughter-in-law and I recently noticed many large old trees cut down or fallen. It looked as though some were cut for firewood. What is going on? — Nadia Abraham, of Springfield

Answer Man: Why are trees coming down at the Springfield Nature Center?

With my iPhone and your question in hand, Nadia, I took a 2-mile hike Wednesday on the Long Trail at the Springfield Conservation Nature Center, run by the Missouri Department of Conservation.

I saw many downed trees. I saw many fresh stumps. I even saw stacked firewood.

But it was difficult for me to discern how long a stump has been a stump or how long a tree has been down.

Regardless, using my considerable tracking skills, I tracked down a knowledgeable source at the center, and I think I have your answer.

The center is losing oak trees to an opportunistic fungus that attacks mature oaks under distress.

Eric McMillan, maintenance supervisor

The killer is a common disease called hypoxylon canker, says Eric McMillan, maintenance supervisor at the center.

"It hit us a few years ago," he says.

The disease has killed approximately 20 mature oaks at the center in the past three years. People have noticed the loss because most of the oak trees stricken have been big and prominently located.

"It does not hit small trees," he says. "It hits larger trees. ... They are significant trees.

"By the time you see it, that tree is going to die."

Yellowing and wilting leaves can signal the onset of the disease, but such symptoms are general indicators that a tree is stressed, not necessarily that it has been hit by the fungus.

The most recognizable sign of hypoxylon canker is the sloughing off of bark on branches or trunks. This exposes a silvery layer of fungus.

The fungus enters through wounds on branches or trunks and it grows in the sapwood, killing the conductive tissue.

Answer Man: Why are trees coming down at the Springfield Nature Center?

Prior to the loss of bark, there often are sunken areas where the fungus has killed the tree's cambium, which is a layer of cells that helps the tree grow.

According to the Missouri Botanical Garden website, there is some evidence the fungus invades young trees but does not cause a problem until the tree is under stress.

Diseased trees typically die in one to two years.

Many oaks are susceptible in the Ozarks, McMillan says, because of recent drought conditions.

At the nature center, McMillan says, a main concern is that dead or dying limbs — called "widow makers" — will fall from tall trees and injure hikers.

"You've got to get to it quick," he says. "The longer you wait, the more hazardous it becomes."

When a diseased tree is away from hiking trails and poses no risk of crashing downhill, McMillan says, he has let it stand but tops it off — meaning the limbs are cut off.

"They make good den trees for squirrels and woodpeckers," he tells me.

Some of the diseased oak trees are cut down and then cut into firewood.

Those near trails are cut to a stump are then sliced into firewood. Stacks of firewood are on the center's grounds.

Firewood from infected trees is safe to burn. But firewood, in general, should not be moved great distances. Keeping the wood local prevents the spread of invasive pests such as the emerald ash borer, a beetle.

The best prevention against hypoxylon canker is to keep oaks healthy in the first place. The fungus is unable to harm healthy trees but is quick to colonize weakened or dying bark and wood.

Avoid damaging trees during construction projects, and water them during times of drought.

Answer Man: Why are trees coming down at the Springfield Nature Center?

One final note, Nadia.

As you hike the Nature Center trails, don't assume every downed tree or fresh stump is caused by hypoxylon canker.

I happened to speak to McMillan the day after a violent storm hit the area the night before, knocking over trees throughout the city.

Seven young trees fell victim in the Nature Center, McMillan says. This had nothing to do with the fungus but everything to do with high winds.

Keep those questions coming. Send them to The Answer Man at 836-1253, spokin@gannett.com, on Twitter @stevepokinNL or by mail at 651 N. Boonville, Springfield, MO 65806.  

The Answer Man Archives: Feb. 1, 2015 

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