Winter of 2009-10 didn't phase pesky pine beetle

By Cherry Sokoloski
North Forty News

For a tiny bug measuring 5 or 6 millimeters in length, the mountain pine beetle has done a huge amount of damage in Western forests. Forest Service officials estimate that 3.6 million acres in Colorado have already fallen victim to the beetle, and the bug isn't done with its killing spree yet.

It's always good to know the enemy, so the North Forty News consulted recently with a local mountain pine beetle expert, Dr. Donald Bright, to better understand the pesky predator. A retired entomologist, Bright began studying the beetle 55 years ago, when he was an undergraduate at Colorado State University.

Bright spent most of his career with the Canadian National Collection of Insects in Ottawa, Ontario. He noted that the beetle has also devastated forests in Canada, wreaking great economic damage.

"We're witnessing a pretty massive natural occurrence," he commented.

Bright explained that several weather-related factors have influenced the spread of the pine beetle. However, this past winter was not one of them.

Since it was unusually cold in northern Colorado this year, some folks with mountain properties have wondered whether their pine beetle problems are over. Not so, said Bright. Cold winter weather can kill off the insects, but it has to be extreme: 30 below zero for five days or more.

In winter months, pine beetles are in the larval stage, snugly settled in beneath the bark. The larvae actually produce antifreeze in their bodies, and as it gets colder, they produce more of the chemical. That's why they're well protected from the cold. However, sudden cold snaps in fall or late spring can do them in, because the antifreeze protection is weaker at those times.

Now that the snow is gone, it's time to check lodgepole and ponderosa pines on one's property, and to treat the ones that were attacked last summer by the mountain pine beetle. Infested trees must be cut down and chipped, burned, peeled or solar-treated.

To protect healthy trees, Bright recommends spraying in late spring – before adult beetles fly to new trees in June and July. Many people do their own spraying, but there are also several companies in the area that can be hired for the job. Bright stressed that the entire stem of the tree needs to be covered with the chemical, up to a height where the tree is about 5 inches in diameter.

The Colorado State Forest Service has compiled a list of products used for pine beetle prevention, with pros and cons about each. The list can be found at www.csfs.colostate.edu/pdfs/mpb-prevention-products.pdf.

Spread by wind

Bright said that pine beetle watchers have a theory about how the beetle infestation spread so quickly across the Continental Divide and into the Front Range. One possible reason is another weather phenomenon.

It is well known that clouds of beetles can be blown many miles by the wind. Beetle researchers believe an especially big wind event blew huge numbers of beetles from the West Slope over the Divide, along a northeasterly path.

Rocky Mountain National Park, the Red Feather Lakes area, Cheyenne and western Nebraska all suffered from massive pine beetle outbreaks in 2008.

"These areas fall along a direct line," Bright pointed out, adding that without such a windstorm, it would have been very unusual to see such rapid beetle movement in a year's time.

Assistant Fort Collins forester Ralph Zentz cites a similar wind event in late summer 2008 that likely blew beetles into the city. Before that year, Fort Collins trees had suffered only minor beetle hits, but about 600 trees were attacked in 2008.

Life cycle changing

There's yet another weather pattern that's influencing beetle behavior: global warming. Pine beetles' life cycles depend on temperatures, Bright noted, so warmer winters can result in higher survival rates for the beetles.

Pine beetles have had a one-year life cycle in Colorado. However, while data are still inconclusive, some researchers believe that the bugs may now be producing more than one generation per year because of climate change. That could mean that some beetles are flying twice a year, which would be bad news for those trying to control the infestation.

"It only stands to reason that global warming will have some effect on pine beetles," Bright said, either in terms of a higher survival rate or a faster life cycle.

At any rate, Bright said, "the mountain pine beetle is not acting like it used to." Scientists aren't sure whether the changing life cycle is caused by global warming or the massive competition that comes with an epidemic of this size.

"It's an evolving situation," Bright said.

But for property owners dealing with the bug, much will look the same this summer as they get out their chainsaws, chippers and sprayers. Cut, burn, chip, spray. Repeat.

Dr. Donald Bright is a volunteer at Colorado State University's C.P. Gillette Museum of Arthropod Diversity. The museum's director, Dr. Boris Kondratieff, gives frequent presentations about insects at local schools. For more information about programs, call 491-7214.