January 30, 2012 in Outdoors, Idaho, Region

Tussock moth infestation hits Inland Northwest

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Tussock moths chewed their way across 68,000 acres of the Idaho Panhandle last summer, leaving behind red-topped trees.

The native pests primarily attack Douglas-fir trees, grand fir and subalpine fir trees. Aerial surveys indicate that the moth outbreak also affected 1,600 acres in eastern Spokane County and about 9,000 acres in the Blue Mountains of southeast Washington and northeast Oregon, according to the Washington Department of Natural Resources.

Tussock moth outbreaks typically peak in 10 year cycles. The outbreak in Spokane County will probably subside this year, but the Idaho Panhandle could see an increase in the number of acres affected, forest entomologists predict.

Tussock moth caterpillars feed on both old and new foliage. Though the trees appear dead, many survive if they can form buds that can last through the winter. However, repeat defoliation can stunt tree growth, cause top-kill and may make trees more susceptible to later attacks from bark beetles.

Outbreaks typically collapse within two to four years, due to a build up of natural enemies, including a viral disease. Birds and parasitic wasps also help keep tussock moth populations in check.

Six comments on this story so far. Add yours!

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  QueenofSanDiego on January 30 at 12:55 p.m.

  The Tussock has decimated the Blues….it breaks my heart.

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  westerly on January 30 at 1:10 p.m.

  Mother nature at work…for eons..

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  RedCedar on January 30 at 3:44 p.m.

  These insect outbreaks aren’t entirely natural. Left to nature, we’d have more forest fires, especially where the trees have been killed or injured by bugs.

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  Lulubelle on January 30 at 4:52 p.m.

  more good news from Idaho

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  Justsayin' on January 30 at 7:30 p.m.

  I hope the state and federal entities are allowed to treat to mitigate the pending destruction of OUR forests. Based upon past experience, it is more likely the enviro-radicals will impede any constructive procedures.

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  RedCedar on January 30 at 7:54 p.m.

  Last time around (the mid—70s as I recall), there was a big environmental fight to stop the Forest Service from spraying DDT to kill the moths. The spraying was stopped, and in the subsequent hot summer there were some pretty bad fires. I think the big Hells Canyon fire was one of them. It’s hard to say that the lack of spraying caused the fires though.

  I have seen some areas where practically ever needle was eaten off the first by these bugs, so they are definitely a plague. The question is whether the trees will survive. Next year we’ll find out whether they green up or not. The trouble is there isn’t really any good way to “treat” bug-infested forests. All the insecticides are toxic to other living things too, and even if you only care about the trees, a big dose of insecticide sprayed all over the forest kills the things that eat the caterpillars as well, including birds. It generally throws everything out of whack for many years.

  Probably the best protection against forest pathogens of all types is diversity. If you have a variety of species and a variety of age classes, no one bug is going to devastate the whole forest. In this sense, commercial timber plantations are at a bigger risk than natural forests.