Fall freeze cause of spring's w. juniper damage and dieback

May 15, 2003

Branch of juniper tree damaged by freeze damage.PRINEVILLE - A wide scattering of western junipers in central and eastern Oregon are showing increasing signs of freeze damage and dieback this spring. And that could be bad news during the next wildfire season, say Oregon State University scientists who are monitor the problem.

Reports of red, dying junipers are coming in from Harney, Grant, Wheeler, Deschutes, Crook and Jefferson Counties, according to Tim Deboodt, staff chair of the Crook County office of the OSU Extension Service.

"The calls started trickling in about six weeks ago and now it has turned into a tidal wave of calls," Deboodt said. "The first sightings were on south-facing slopes. We are now seeing a red tint on all slopes, not just those that are south facing."

The juniper freeze damage is showing up as reddish brown, crumbling foliage. Some young trees have turned completely red, while some of the older trees suffer from dead foliage in crowns. The foliage death seems to start at the top of the junipers and works its way down, the scientists say.

"As you grab the needles, they crumble in your hands," Deboodt said.

Deboodt and other OSU researchers hypothesize that the juniper damage and dieback are from freeze damage from a severe cold snap last fall.

"On the 29th of October, a cold air mass moved in from Canada," said Deboodt. "For the next four days, overnight lows were around zero. OSU climatologist George Taylor reported that Seneca recorded minus 11 degrees on Oct. 31. And I've heard that Fort Rock and Christmas Valley got to minus 20 degrees."

Deboodt collected foliage, branches, stems and roots from damaged and dying junipers to be analyzed for disease or pest problems at OSU's Plant Clinic in Corvallis. There was no evidence of any diseases or pests, according to OSU plant pathologist Melodie Putnam.

"I did not see any evidence of any foliage, branch, stem, or root disease," said Putnam. "This is definitely not a disease problem."

Last fall's freeze damage wasn't apparent until spring because the junipers are fairly inactive until the weather warms up, explained Steve Fitzgerald, forester with the Deschutes County office of the OSU Extension Service.

"It takes several months for the foliage to dry out and show the extent of the damage," said Fitzgerald.

The verdict is still out on how widespread the damage and dieback will become.

"As spring changes to summer we'll have a better idea of the damage that was done," said Katie Kause, urban forester with the Oregon Department of Forestry in Prineville.

Foresters and range experts worry that the widespread juniper die-off may contribute to fire hazards this coming summer and fall.

"Unless there are high winds and high temperatures, I think that healthy juniper stands are relatively fireproof," Deboodt said. "But when large, continuous blocks of trees die, what is the risk of wildfire? When they are holding dry needles that can burn like gasoline, what are we looking at?"

To avoid increased fire hazard, Kause and OSU Extension forester Stephen Fitzgerald recommend that property owners with dead junipers remove them and take them to a landfill.

If there is only partial dieback, then junipers should be pruned.

"Some of the junipers have not died, but have branches that were affected adversely from the freeze and have died back," said Kause. "In this case landowners will want to consider only removing the dead branches by making selective pruning cuts, rather than removing the entire tree."

For more information about juniper dieback or depositing landscape material at the local landfill, call your local county office of the OSU Extension Service or your local landfill.

Author: Carol Savonen
Source: Tim Deboodt, Stephen Fitzgerald, Melodie Putnam