RENO, Nev. — Agriculture and forestry experts in Nevada, Utah and California are concerned about a potential infestation of a small white moth that can destroy entire groves of aspen, cottonwood and willow trees, especially in mountainous areas.
The white satin moth numbers are up 100-fold this year in some parts of Nevada, and no one is sure why.
The good news is experts from the three states who studied the moths near Lake Tahoe this month found signs their natural predators are making a rebound and should help keep the invaders in check.
A cousin of the infamous gypsy moth that has seriously damaged forests in the northeastern U.S. and Upper Midwest, the white satin moth is found across most of the northern half of North America. It likely arrived from Europe in the 1920s, scientists say.
Previous outbreaks were reported in the early 2000s in Wyoming and Colorado, but the moth had been flying largely under the radar in the Great Basin region until recently, according to Jeff Knight, state entomologist at the Nevada Department of Agriculture.
“I’ve been doing this 35 years and I was here when the first one was found (in Nevada) and I’ve never seen it as an issue before,” Knight said Wednesday
“It has been more of a curiosity when somebody brings in a nice big white moth into your lab for identification,” he told The Associated Press. “It’s probably been held in check by natural predators and parasites out there, so with this infestation in the past year or so, things have gotten out of balance.”
“I think everybody is kind of concerned now in this area,” Knight said.
The estimated 300 acres of trees impacted in Nevada a year ago has grown to tens of thousands of acres in the most recent surveys, state officials said. Increased damage also has been reported in eastern California and the Sierra.
“There’s an explosion of them,” said Gail Durham, forestry specialist with the Nevada Division of Forestry.
“We are seeing 100-fold what we saw last year,” she told KRNV-TV in Reno earlier this week. “We really want people to watch for them. If you see the eggs, the cocoons or the moths please call and report it so we can continue to map where they are showing up.”
Knight said it’s not clear whether such things as drought, wildfires, climate change or any other number of factors have contributed to the infestation.
“You could probably point to all those things to get into an argument. But we don’t know enough about the population dynamics of this, at least from what I can find,” he said.
The biggest populations have been reported around Lake Tahoe, but also around Fallon and Battle Mountain and as far east as Elko, Knight said.
A group of entomologists and forest experts from Utah, California and Nevada toured the Spooner State Park above Tahoe’s east shore recently and collect samples of caterpillars, cocoons, moths and the known parasites that generally keep them in check, including wasps and certain types of flies. The leaf-eating moths have caused noticeable damage there where lower leaves are laden with nesting larvae and leaves in the tree tops are lacy and eaten.
“Their much preferred host is the aspen. That’s what they really like to feed on and that is where you see their populations develop. But they also attack other poplars. They defoliate the leaves,” Knight said.
The scientists were encouraged by their findings in the Tahoe surveys, he said.
“We looked at stuff yesterday and were seeing parasites actually in the field. You usually have to collect them in bunches of stuff and then root them out,” Knight said Wednesday.
“So that means their populations are probably pretty healthy, and that is a good thing,” he said. “They may not be able to take care of it this year or next spring. But at least we know they are functioning.”