Officials in Minnesota and Wisconsin are asking for the public’s help in stopping the spread of some uninvited holiday guests: invasive, tree-eating insects on wreaths, swags and other holiday decorations made with evergreen boughs.
“People are fine to leave the decorations up through the season, but when it’s time to dispose of them, we’re asking them to burn it or bag it,” said Donna Gilson, a spokeswoman with the Wisconsin Department of Agriculture.
The insect — called elongate hemlock scale, or EHS — was found shortly after Thanksgiving on evergreen arrangements sold at Menards, Home Depot, Kmart, Pick ‘n Save and Stein’s stores in Wisconsin. Once discovered, the infested items were pulled from shelves.
Minnesota tree inspectors on Thursday found the critters on decorations in several Home Depot and Menards stores in the Twin Cities, said Allen Sommerfeld, a spokesman with the Minnesota Department of Agriculture.
“We hadn’t found this insect in Minnesota before,” Sommerfeld said. “It has the potential to impact the state’s coniferous forests and urban and suburban landscapes.”
The infested products came from four evergreen suppliers, all located in North Carolina.
EHS is native to Asia and was introduced into Michigan and many Eastern states. The insect feeds on a variety of conifers, damaging the trees by sucking nutrients from the underside of their needles. Weakened trees are then more susceptible to other pests and diseases.
“We’d been on the lookout for it for the last five years,” Gilson said. “But this year was enough to raise a red flag for us that we needed to get ahead of it.”
EHS bugs are not deterred by cold weather, said Brian Kuhn, director of the Plant Industry Bureau in the Wisconsin Department of Agriculture.
“If you compost this material, the insects may well attack conifers in your yard or neighborhood, and spread from there,” he said.
Though a few isolated cases were identified during holiday season inspections in years past, this year is the first that big-box retailers across Wisconsin have actually sold infested items, she said.
EHS is not a regulated pest in the United States, meaning there’s no law against moving it across the country.
“Certainly no one set out to bring this here, and the stores brought in the product legally,” Gilson said.
Those who still have a wreath or swag on their door need not panic, though the reason may be a bit unpleasant to think about.
While the insect is feeding or pupating, it secretes a cover around itself, creating a kind of waxy, protective scale. That means you likely won’t have insects crawling around your home anytime soon, even if your decoration is infested.
To check for signs of EHS, look for those scales, which appear as small brown spots on the underside of needles.
That protective layer also makes EHS hard to get rid of with spray-on pesticides. If Christmas tree farms in Minnesota or Wisconsin become infected by the invasive insect, the cost of injecting trees could cause their price to rise significantly, Gilson said.
“We have been lucky so far,” she said. “We can probably chalk that up to diligence.”