Are we in for a blizzard of winter moths?

By Tim Forsberg
Posted 12/7/16

While Monday brought the first snowflakes of the season, flurries of winter moths are again making their presence felt across the region. Originally from Europe, the invasive species known by its scientific name - Operophtera brumata -

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Are we in for a blizzard of winter moths?


While Monday brought the first snowflakes of the season, flurries of winter moths are again making their presence felt across the region.

Originally from Europe, the invasive species known by its scientific name - Operophtera brumata – made its first appearance in the state around 2004 and has been relentlessly prolific since.   Part of a one-two moth punch this year that included a gypsy moth infestation, which decimated local trees, winter moth adults are now emerging from the ground where they’ve developed throughout the summer.

“It’s been a very rough couple of years for trees. It’s been a very tough time to be a tree,” said Heather Faubert, a research assistant at the University of Rhode Island’s Department of Plant Sciences and Entomology, and a local expert of the insect.

Typically, this week is the peak time for moths to emerge, and now they have only one thing on their minds: mating.

“It seems like we’re having a big flight again this year, and we had a huge flight last fall, and then we didn’t see very many caterpillars really this spring,” said Faubert. “I’m not sure why that was, but we had very strange weather in the spring where it warmed up quickly and the eggs stated hatching very early. Usually the eggs hatch over about a week’s period of time, but this year it was over about three to four weeks. It warmed up and pushed everything ahead, and then it got cold and they started to trickle out.”

Faubert partners with researcher Joe Elkington from the University of Massachusetts to study the moth, and they’ve theorized that this year’s strange spring weather that coincided when the moth eggs hatched and when the trees began to bud may have been off, but are uncertain what if any impact it had on the moths.

The dry spring and summer also helped the gypsy moth population soar, as a fungus that attacks that species and helps regulate their numbers needs a wet environment early in the year to thrive. Without the fungus, the population boomed.

Winter moths have peculiar life, emerging as caterpillars in the spring from eggs laid in trees during the previous winter. The small green worms then burrow into a tree’s buds before they become leaves and eat their fill before dropping to the ground and burrowing into the dirt to cocoon. Moths become adults around the time of the first frost in late fall or early winter. Warm nights, usually after the first hard frost, trigger moths to emerge from the ground where they’ve metamorphosed throughout the summer.

The males are the ones seen flying around lights and buildings. The females are flightless, remain largely unseen, and immediately climb trees to put out pheromones that attract the males to begin the life cycle again. The moths do not eat as adults.

Unfortunately, at this time of year, most methods of pest control against the moths are largely ineffective. Recent reports have advised homeowners to place a physical barrier around the trunks of trees to prevent the females from climbing them, but Faubert isn’t convinced that method will work. 

“It does certainly stop some females, on one tree at URI last year I put two bands, one at knee height and one at waist height. On the lower band I caught 207 females, on the next band up I caught 138, so who knows how many got past the second band,” she said.  “There are commercial tree wraps that you can buy, and then there’s this stuff called BugBarrier, which is real expensive but it works nicely and it’s what I use to stop some females and it helps to congregate the eggs so I can watch them hatch in the spring.”

Online comments from news articles and social media about the moths have suggested scrubbing tree trunks with brushes to remove eggs, or vacuuming the males in an effort to curtail the population.

“Well that’s certainly a waste of time, but it makes people feel better, and how can you quantify it if somebody feels better,” said Faubert.

Spring is the time that residents can best attempt to control the population. Insecticides that target the moth, such as Spinosad, or a Bt product – Bacillus thuringiensis – only work when the moths are caterpillars and can eat the toxins.

Other efforts to stop the moth are underway in the state. A fly called

“In Rhode Island where we’ve released them at seven locations, we’ve still only recovered them at one location, Goddard Park, the next year,” said Faubert, who helped spearhead the fly project. “So it’s slow going. I’m hopeful for next year, but that’s kind of what I say every year, because we still haven’t seen a decline.” 

Faubert also said that the areas natural predators, such as spiders and songbirds, are having lots of fun with the caterpillars in the spring and are including them in their diets. But those bothered by the moths now will have to wait until the holidays for this unwanted guest to leave.  

“Usually by Christmas, the moths are gone,” said Faubert. 


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