Bluegrass Park trees fighting wilt disease - Coeur d'Alene Press: Local News

Bluegrass Park trees fighting wilt disease

Ten sugar maples have already been removed by the city

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Posted: Saturday, June 23, 2012 12:00 am | Updated: 11:23 am, Fri Nov 16, 2012.

COEUR d'ALENE - It's called verticillium wilt disease.

What it is, is a death sentence in the world of trees.

Where it is, is Bluegrass Park in Coeur d'Alene.

What can be done, unfortunately, is very little.

"Once a tree gets infected, it can live for a few more years," said Katie Kosanke, urban forestry assistant with the city, on the life span of a stricken tree. "Unfortunately, there are no treatment options."

Already, 10 sugar maples at the 11-acre park have been pulled because of the disease, which survives in cultivated soil and spreads from tree to tree beneath ground along root routes.

But even removing trees won't cure the park of its problem. As the fungus survives underground, there's no telling how far it can or will spread.

"It can be transferred through the roots because the root system grows wide and not deep," Kosanke said.

Like fingers from different germy hands reaching out and touching each other, so is the avenue to spread below the surface.

The city suspected the problem about a year ago when it noticed limbs on trees dying off individually. That's how the disease works, it inhibits water intake for trees so branches slowly wilt away one by one. As the pattern persisted, the suspicion grew. Conformation finally came a couple of weeks ago after a forest pathologist examined samples.

Count disc golf enthusiast Gerald Parker among those who don't want to see the disease spread and more trees die. He tosses discs at the Bluegrass Park course two or three times a week, and noticed at least one of the trees had been removed, because it had been a landmark around which golfers had to navigate.

"It's an enhancement to have all the trees," he said. "It makes you become skilled and accurate."

It costs roughly $300 for the department to remove and replace a tree.

If the bad news is there's no cure for the disease, and no telling how far it can spread, the good news is not every species is susceptible. The city's parks department works with 66 different tree species around town, so it will replace lost trees this fall with a fungus-proof stock, probably of the oak or fir variety.

Nearby neighbors have been notified.

Meantime, the best way to prevent the disease is to keep nearby trees healthy, as, just like with humans, the healthier variety are more likely to resist a disease. Another thing arborists can do is sterilize pruning equipment after each use. If tools have touched an unhealthy tree, they can spread the disease when the contact a healthy one.

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1 comment:

  • yarply posted at 1:37 pm on Sun, Jun 24, 2012.

    yarply Posts: 485

    Verticillium wilt is difficult to control because it persists in the soil indefinitely. Infected trees that are not yet dead sometimes “outgrow” the fungus. Dead branches should be pruned out to help overall plant vigor. The disease can be transmitted on pruning tools. It is recommended that tools be sterilized by dipping them in a diluted cleanser, such as Lysol, Pinesol, or household bleach, between cuts and between trees.

    To avoid stress, trees should be planted in sites that are favorable to their growth. Water thoroughly during dry periods. Use a three- to fourinch layer of organic mulch to retain moisture and prevent soil temperature fluctuation. Fertilize properly and avoid injuries to the roots, trunk, and branches. Severely infected trees should be removed and replaced with plants that are not susceptible to Verticillium. Trees that are not known to be susceptible include: arborvitae, baldcypress, beech, birch, boxwood, crabapple, ginkgo, hackberry, hawthorn, hazelnut, hickory, holly, honey locust, hornbeam, ironwood, Katsura tree, mulberry, oak, pine, serviceberry, spruce, sweetgum, walnut, willow, and yew.

    At this time, there is no known chemical control for this disease. Injections with systemic fungicides may alleviate the symptoms; however, the soil-borne nature of the disease precludes this from being an effective long-term control.

    source: The Morton Arboredum

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