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Moths Threaten Lake Tahoe's Fall Colors

Nevada Department of Conservation and Natural Resources

Satin moths are destroying aspen trees in Northern Nevada.

If you're not familiar with the satin moth, picture the snow queen from "The Lion, the Witch and the Wardrobe" — with wings.

That's what the moth looks like. It's a frosty white-winged insect that seems to be wearing a white fur scarf. 

It's beautiful, but it's also bad for trees.

The biggest problem is the moth is non-native and therefore doesn't have any natural enemies.

“With not too many native predators for this species that’s what makes it invasive and it can build up populations very quickly,” Gene Phillips, a forest health specialist with the Nevada Division of Forestry, told KNPR's State of Nevada.

The moth first appeared in the Pacific Northwest but quickly made its way southeast to Nevada's forests.

While the moth has been around since the 1980s, the population over the past couple of years has been growing.

“In 2017, we saw a large uptick in the populations from its lower levels the previous three years and this year, 2018, based on caterpillar counts last fall, we’re looking at an increased population again this year, causing heavy defoliation in some of the same aspen stands and some surrounding stands,” Phillips said.

Phillips is not sure why the population has been increasing but insects that eat the leaves off trees, known as defoliators, do have a boom-and-bust lifecycle.

Because the moths don't damage the bark or trunks of the trees, they don't kill the trees outright. However, Phillips said if trees are repeatedly stripped of their leaves they will die.

“Unfortunately, some of this will be trial by error," he said, "We’re going to see how much mortality may occur in these areas right now based on the current uptick in population and we won’t know that for a few years."

The Division of Forestry along with several other state agencies and the University of Nevada, Reno are working on a three-year study of the moth in hopes of finding a way to combat it.

There are insecticides that can combat the moths but coordinating those efforts with land managers and regulations can be difficult. Plus, many people worry about the damage spraying can have on other insects in the forest.

Phillips said there will be very little fall color in the forest around Lake Tahoe this year because of the damage inflicted by the moths. 

People who visit the area will see the damage, “...Since it is right here, where there is high recreation use and population, it is going to be noticeable and a concern of land managers.”

Phillips is concerned that if trees start dying off because they've had their leaves eaten away by the moths year after year then it will create a safety concern along hiking trails and walking paths.

Gene Phillips, forest health specialist, Nevada Division of Forestry

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Kristy Totten is a producer at KNPR's State of Nevada. Previously she was a staff writer at Las Vegas Weekly, and has covered technology, education and economic development for the Las Vegas Review-Journal. She's a graduate of the Missouri School of Journalism.