First detection of this invasive bug in the state
“It’s not known how BWA may have gotten to Michigan or how long it’s been here, but it’s plausible it was on infested nursery stock,” said McDowell. “Arborists, tree experts and the public are our extra set of eyes with invasive species. With August being National Tree Check month, this is another critical reminder to look for irregularities with your trees and to not move firewood.”
Balsam woolly adelgid is a tiny, sap-feeding insect that attacks true fir trees, including balsam, Fraser and concolor (white) fir. BWA has been on Michigan’s Invasive Species Watch List for years because repeated attacks from the pest weaken trees, cause twig gouting, kill branches and, over the course of many years, cause trees to decline or die. Although new to Michigan, BWA has infested fir trees in portions of the United States for over 100 years, likely arriving on infested nursery stock from Europe.
Symptoms of BWA infestation include:
- Tiny 1- to 2-millimeter, white woolly tufts on the lower trunk of the tree and possibly on large branches in the spring and summer.
- Swelling and distortion of the twigs, commonly called “gout.”
- Flagging – A branch or branches that turn brick-red and die.
- Tree crowns that become narrow and misshapen with few needles.
In 2014, MDARD implemented a balsam woolly adelgid quarantine regulating the movement of potentially infested nursery stock from areas in North America with known infestations.
“This invasive insect is a threat to the nearly 1.9 billion balsam fir trees in Michigan’s forests,” said Rob Miller, PPPM’s invasive species prevention and response specialist. “And, as the third largest Christmas tree-growing state in the country, Michigan produces nearly 13.5 million fir trees each year, which are susceptible to balsam woolly adelgid.”
Although not native to Michigan, Fraser and concolor fir trees are often planted on home landscapes. Balsam fir is native to the Upper Peninsula and northern Lower Peninsula but also found throughout the state in residential and park settings.
As more and more people spend time outdoors, the potential for spreading balsam woolly adelgid and other invasive species also grows.