Douglas Fir Moths causing fir trees to turn red around Missoula

MISSOULA - While pine beetles are devastating forests around Montana, some trees on Missoula mountains are turning red because of a different threat.

Scientists say Douglas Fir Tussock moths and their larvae are causing large patches of fir and spruce trees to turn red.

"They are a really aggressive defoliator and the damage we see from the roadside is really apparent, and in big bloom years we tend to take a lot of notice," says August Kramer, a Forest Pest Specialist with the Department of Natural Resources.

Some tell-tale signs of the Tussock Moths are silky webbing on your fir trees and the browning of needles on the ends of branches. The larvae are even easy to spot if you take a close look at the tree.

"We have been seeing them in the Missoula area historically, but what makes this year a little bit different is that we are seeing it in new parts of Missoula," Kramer said.

Places like Mount Dean Stone, the Rattlesnake, and Black Mountain. But the long-term effects might not be as bad as it looks.

"The population has a naturally occurring virus that builds up over the course of three to four years, and by that third or fourth year, the population gets decimated and it’s no longer a problem,” Kramer said.

The DNRC believes the moth has already been in the area for two years so by this time next year the problem could resolve itself.

“They may kill smaller understory trees, but adult trees should be okay more or less," Kramer said.

There are chemical treatments that will kill the moths and larvae but as of right now the DNRC isn’t going to take any action.

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