Invasive insect that infests hemlock trees found in seventh Michigan county

An invasive insect that infests hemlock trees has been found in another northwest Michigan county, the Michigan Department of Natural Resources said Monday.

State agricultural officials identified the bug, hemlock woolly adelgid, near Antrim County's Torch Lake, making it the seventh Michigan county with the insect. They haven't determined the size of the infested area, the DNR said, but have undertaken "an extensive survey of the surrounding area."

Hemlock woolly adelgids are similar to aphids. They eat sap from hemlock trees, which weakens the trees' needles, shoots and branches. Infested trees turn gray-green and, without treatment, can die in four to 10 years.

They form round, white egg sacks on the underside of eastern hemlock twigs at the base of needles. They look like small cotton balls and are most visible from November through July.

The insects are from east Asia and have been identified in at least 20 states. They likely came to Michigan through infested nursery stock from the northeast U.S.

In Michigan, the bugs have been found mostly in the west and northwest Lower Peninsula in Allegan, Benzie, Mason, Muskegon, Oceana and Ottawa counties. It also has been identified in southeast Michigan's Washtenaw County.

Michigan has an estimated 170 million hemlock trees, said Steve Carlson, Pesticide and Plant Pest Management Division Director for the Michigan Department of Agriculture and Rural Development.

A landowner identified the Torch Lake infestation after learning about hemlock woolly adelgid at an educational event hosted by a regional invasive species management team, Carlson said. That shows the value in teaching the public about invasive species, he said.

"Though the tiny insects don't move far on their own, they can be blown by wind or hitchhike on animals. In a similar way, cars, boats, or RVs parked under infested trees may be able to transport the insects to new locations," Carlson said in a DNR press release. "If you're headed outdoors, take simple measures like only parking in designated areas and cleaning your gear and vehicle before traveling. Also, remember to leave firewood at home and buy it locally at your destination."

To report a possible infestation, contact MDARD at MDA-Info@michigan.gov or (800) 292-3939, or use the Midwest Invasive Species Information Network online reporting tool at misin.msu.edu. Be prepared to report the location of the infestation and take pictures of the infestation to confirm identification, but do not collect samples, the DNR warned.

ckthompson@detroitnews.com