Idaho white pine

A University of Idaho Extension workshop June 21 will help forestry professionals and family foresters prune western white pine and increase its numbers.

An upcoming workshop will teach forestry professionals and family foresters how to restore the western white pine, the official state tree.

The "Pruning to Restore White Pine" workshop will be 9 a.m. to 5 p.m. June 21 at the Inn at Priest Lake, 5310 Dickensheet Road, Coolin, Idaho.

White pine populations were dramatically reduced in the early 1900s due to blister rust, a non-native disease, said Chris Schnepf, University of Idaho Extension forestry educator.

One way to help is breeding white pines resistant to the disease. Inland Empire Tree Improvement Cooperative efforts are in the second generation of the program and beginning on the third, Schnepf said.

"Those white pine seedlings will resist blister rust pretty dramatically compared to the natural seedlings," he said.

Pruning native white pine up 10 feet can reduce blister rust mortality by half, Schnepf said. 

The disease has a "complicated" life cycle, with five spore stages. The spore stage that affects white pine through its needles needs 100% humidity to successfully infect the tree.

Such conditions are most likely to be found closer to the ground.

The program includes information about the trees and the disease, and field demonstrations of tools and examinations of sites where white pine has been pruned, with canker identification.

Schnepf doesn't recommend thinning white pine without pruning, which is usually good for a young stand of trees.

"If you thin white pine without pruning, you can actually make blister rust worse," he said.

Forest owners might see other benefits to pruning, he added.

"For many private landowners, it's a high satisfaction activity that you see immediate results from," he said.

The goal is to increase white pine populations. Schnepf said. 

Until recently, white pine was the most valuable tree in the woods, Schnepf said. But prices aren't as high due to the loss of supply and markets.

"Personally, I believe we can get those markets back if we have adequate supply," he said. "White pine has wood characteristics that are very dissimilar from very many other species in the world. It's real low-resin wood that has a lot of useful wood product characteristics." 

When white pine was lost in forest ecosystems, the next species that filled the niche were grand fir and Douglas fir, which are both vulnerable to root disease. 

"You can make the case that blister rust also increased root disease in our area," Schnepf said. "All trees can get killed by root disease species, but white pine is much more tolerant of root diseases."

The program is co-sponsored by University of Idaho Extension, the Idaho Department of Lands and the U.S. Forest Service. 

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