Wisconsin wreaths carry invasive insects from eastern states

Wisconsin residents are being asked to burn or bag some Christmas decorations after an infestation of highly invasive tree-eating insects were found on wreaths, swags and other holiday items made with real evergreen boughs.

State tree inspectors on Wednesday said they found the tiny insects, called elongate hemlock scale, or EHS, on wreaths, swags and boughs as well as evergreen boughs used in hanging baskets, porch pots, mugs and sleighs sold at several big box retail stores statewide.

It's unclear how many infested items were sold.

"Burn them if you can. If you can't do that, bag them and send them to the landfill," said Brian Kuhn, director of the Plant Industry Bureau in the Wisconsin Department of Agriculture, Trade and Consumer Protection. The insect already has survived Maine winters "so winter weather will not kill it. As a result, if you compost this material, the insects may well attack conifers in your yard or neighborhood and spread from there."

Inspectors found the insects on decorations made with real evergreen boughs sold at Menards, Home Depot, Kmart, Steins and Pick N' Save. The stores cooperated and destroyed any infested stock they had on hand, said Donna Gilson, spokesperson for the state agency. But many infested items were likely sold before the discovery was made.

It's the first time more than a few of the insects have been found in the state. Because the insect especially likes fir, spruce and hemlock it has the potential to damage the state's nursery industry as well as the state's vast forests and urban and suburban landscapes.

"We've found it before but in very small, easily handled numbers. But this year it's so widespread that it has the potential to be a very big deal for Wisconsin trees,'' Gilson said.

The insect, originally from Asia, already has invaded 16 eastern states and is known to damage to more than 40 species of evergreens, Gilson said. The tiny creatures use a hairlike probe to suck nutrients out of each needle. Infested needles eventually turn brown and fall off.

State inspectors this season managed to stop EHS-infested boughs that entered the state from Virginia before they reached stores. But most of the infested boughs appear to have come from four suppliers based in North Carolina, Gilson said. And because they were widely distributed to so many big-box retailers, she said it's "probably likely" infested wreaths and decorations were sold in other states where those stores operate.

Menards and Home Depot operate dozens of stores across Minnesota where wreaths and other evergreen bough decorations were sold, but it's unclear if any of those were infested. Allen Sommerfeld, a spokesperson for the Minnesota Department of Agriculture, said there have been no reports as yet of EHS on items sold in the state. He said Minnesota officials had not heard of the Wisconsin infestation until Wednesday, but he said the advice to burn or bag natural bough items is good in Minnesota, too.

"We would follow the Wisconsin Department of Agriculture's recommendations of bagging or burning greens to stop EHS, gypsy moth, or other potentially invasive insects from spreading," Sommerfeld told the Duluth News Tribune.

Elongate hemlock scale operates on the underside of evergreen needles. They are hard to kill with pesticides, experts say, and the infestations weaken the tree making it vulnerable to other issues. Many of the infested trees perish.

EHS has a complex life cycle with several growth stages. After hatching from eggs, "crawlers" begin feeding on the underside of needles and secrete a waxy brown cover around themselves as they grow, creating the "scale" that is visible. The crawlers may establish new infestations. Wind and birds may also disperse infestations to new trees.

This story originally ran in the Duluth News Tribune.