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April 29, 2014

DNR forest health specialists advise a wait-and-see approach before removing

MADISON - People across Wisconsin have been contacting state forestry officials noting they are seeing some unsightly brown on the evergreen trees along roadsides, parks and yards.

The harsh winter created some serious challenges for cone-bearing conifers and other evergreens this year due to salt and winter drying. Todd Lanigan, plant, pest and disease specialist for the Wisconsin Department of Natural Resources, says there a few telltale signs to look for in determining the source of the damage and appropriate next steps.

"Coming through a difficult winter that forced many communities to increase salt use on the roads, we expected to see some effects," Lanigan says. "As the surrounding vegetation starts to 'green up,' the contrast is even more noticeable to homeowners and motorists used to seeing healthy pines, cedars and junipers."

The use of de-icing salt affects vegetation along roadways through runoff and salt spray. As the snow melts and salty runoff accumulates, entire groups of trees or shrubs near the puddles may show off-color needles. Scattered reddish brown streaks and spots typically result from salty slush that has been splashed up by plows and fast-moving traffic.

In both cases, the discolored needles may eventually fall off. Spruce trees tend to be more tolerant of salt spray and runoff than native pines.

Winter injury - also known as winter drying - represents another contributor to the high number of discolored conifers this year. When the ground is frozen for long periods, the trees are unable to replenish moisture in needles exposed to harsh winds and the winter sun.

Is it possible to tell the difference between salt damage and winter drying? Lanigan says if the tree or shrub is green below the snowline, winter drying is likely the culprit. Discolored needles on the south sides of trees and shrubs also indicate winter drying.

Unfortunately, many evergreens are likely suffering from a combination of salt and winter injury this year. But there is hope.

If the buds are not affected, new green growth will soon appear. Some trees and shrubs are able to sustain damage covering up to half of their surface area and still recover.

"Trees are pretty resilient and do have the ability to recover from some injuries," Lanigan says. "Unless they pose a hazard to a structure or vehicle, don't be in a hurry to remove them. You may find they'll surprise you."

FOR MORE INFORMATION CONTACT: Todd Lanigan, plant pest and disease specialist,; (715) 839-1632; Jennifer Sereno, communications, (608) 770-8084

Last Revised: Tuesday, April 29, 2014

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