For the first time, a destructive invasive insect has been detected in trees at a national forest in Michigan.
The Huron-Manistee National Forests (HMNFs) recently verified the detection of invasive hemlock woolly adelgid (HWA) at Hamlin Lake on January 31 and the Nordhouse Dunes Wilderness Area on February 2, both in Grant Township, Mason County.
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“We used positive sensitive environmental DNA (eDNA) trap locations to focus our detection survey efforts,” said Forest Silviculturist Carol Young. The eDNA trap captures DNA released by organisms through dead cells, feces, mucus, etc. into the environment.
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Hemlock woolly adelgids are small insects. In the fall and winter, the adelgids cover themselves with a white, waxy coating for protection appearing as wool bundles the size of a pinhead at the base of hemlock needles. Infestations are recognizable by the appearance of tiny “cotton balls” at the base of hemlock needles on the underside of the branch. Using their long, siphoning mouthparts, HWAs extract sap from hemlock trees, thereby weakening the tree. Over time, tree growth slows and trees take on a grayish-green appearance.
Without treatment, infested trees die within four to ten years.
Although these tiny insects don’t move far on their own, they can be blown by wind or hitchhike on people, recreational equipment, birds or mammals that encounter an infested branch. In a similar way, cars, boats, or RVs parked under infested trees may be able to transport the insects to new locations.
It is recommended that forest visitors take steps to prevent the spread of invasive species, steps include:
- Leaving firewood at home and buying it where you burn it.
- Staying on trails to protect natural areas.
- Parking in open, paved areas, not in fields or under trees.
- Washing your vehicle and recreation equipment often when travelling between areas in the region.
- Cleaning gear and vehicles before hitting the road.
- Learning to identify Eastern HWA and report it using the directions below.
These insects are considered invasive because they are not native to Michigan and can cause significant harm to the state’s hemlock resource, estimated at 170 million trees.
Hemlock trees are common throughout the region. These trees provide food, shade, and cover for many species of birds and mammals especially important during the spring before other plants have grown back their leaves. Eastern hemlock trees often grow around freshwater rivers and streams. In these areas, their shallow roots help to stabilize the soil and limit erosion. The shade also keeps water temperatures cool for animals like fish and aquatic invertebrates.
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