As part of the ongoing mountain pine beetle battle, the Helena National Forest is encouraging people with land adjacent to the forest to remove green beetle-infested trees near the public-private boundary.

The Forest Service also will send someone to meet landowners to look at the trees on public lands to ensure that the green trees people think are infested actually are home to the mountain pine beetle, which has killed thousands of trees on an estimated 400,000 acres in the Helena forest.

"You can get a permit for dead brown trees for firewood already; the difference here, we want to allow people to cut down the trees that are infested and currently are dead but they're not showing the signs. They're still green," said Amber Kamps, Lincoln district ranger. "It takes about a year for it to turn from green to brown."

Forest officials readily acknowledge that this won't halt the march of the mountain pine beetle across the Rocky Mountains, but it is another tool, along with chemical treatments, to try to keep the insects out of trees on private property.

"It's not going to affect the overall epidemic of beetle populations as a whole, but it does help in small, localized areas," noted Kamps. "If the beetles are just coming into your area, this might help keep them from getting into your trees."

The beetles are a natural part of forest ecology, but decades of fire suppression and years of drought have weakened trees, leaving them more susceptible to the insects and allowing their numbers to grow exponentially.

Beetles land on a tree around August and bore into it, then lay eggs that hatch into larvae. They emerge as fully developed beetles by the following July.

Trees heavily infested with beetles are considered dead, even though they remain green for a year after the beetles fly. So the Forest Service is trying to get people to cut down the green trees while the beetles are still in the larvae form. Theoretically, that way they won't fly to other trees when they mature.

That tactic contains some risks.

Cutting down a tree doesn't kill the beetles. Amy Gannon, an entomologist with the Department of Natural Resources and Conservation, notes that the beetles can stay alive even in wood that's been cut to standard fireplace lengths and split. If the infested green wood is piled until it dries out, the beetles still can emerge and fly to other trees.

"The beetles can fly up to 20 miles," Gannon said.

Worse yet, if the cut wood is stored somewhere else -- say inside the Helena city limits or other places that haven't been hit by the beetles -- it could spread them to uninfested areas.

"It should be chipped, burned or buried, and I don't really recommend burying it," Gannon said. "Don't keep infested firewood."

Kamps and Gannon agree that the beetle larvae also can be killed by stripping the bark from the green trees, but that's pretty labor intensive.

One practice recommended by the Forest Service but not by the state is covering green infested wood with a black tarp or black plastic. That's worked in Colorado and is one option being recommended by the Helena forest, but Gannon is adamantly opposed to it.

"It doesn't work in this climate," she said. "We don't get hot enough here like it does in Colorado."

Helena District Ranger Duane Harp doesn't necessarily agree. He's heard that tightly wrapping the beetle-infested green wood in black plastic in a sunny area is a successful way of killing beetles.

"We'll give people the option to use black plastic," Harp said.

The mountain pine beetle affects ponderosa, lodgepole, whitebark and limber pines, but not Douglas fir.

People who want to cut down the infested green trees need to get $5 per-cord permit, with a minimum of four cords and maximum of 12 cords, which is the same as a standard firewood permit.

They also need to contact the Helena forest's "Bug Line" at 495-3755 and leave a message for a site visit. Priority will be given to landowners who are treating their own property to lessen insect susceptibility and fire hazards. Landowners need to have identified the trees they propose to remove before the site visit.

Trees to be removed must be within 100 feet of the forest boundary, and marked by Forest Service personnel in advance. They can't be used for products other than personal use firewood.

Forest officials add that they've seen an increase in the number of standard firewood permits being issued, and trees taken under those permits must be completely red needled or without needs.

Even if those trees were killed by mountain pine beetles, those insects have left the tree by this point. Other larvae and wood-boring beetles, however, may be present but aren't a cause for concern.

Reporter Eve Byron: 447-4076 or eve.byron@helenair.com