Tiny invasive bug poses a huge threat in Michigan
For Estelle Charroud, a mission to help save Michigan’s 170 million hemlock trees began with one fallen branch in her Holland neighborhood.
That branch was infested with hemlock woolly adelgid (HWA) – a tiny insect that’s one of the most damaging invasive forest pests in eastern North America. The aphid-like insect has killed hundreds of thousands of hemlock trees on the East Coast, from Georgia to Maine, and is now attacking Michigan trees.
And unless Michigan residents band together to stop its advance, its effects could be devastating.
“The more we do right now to contain this, the less chance it’s got to spread,” said John Bedford, pest response program specialist for the Michigan Department of Agriculture and Rural Development (MDARD). “But if we wait until we see dead trees, we’re in a lot of trouble.”
The good news is that unlike the voracious emerald ash borer, the HWA is, on its own, slow moving and treatable. The bad news is that it’s already infecting trees ranging along the Lake Michigan shoreline from Allegan to Oceana counties in areas such as Silver Lake, Muskegon State Park, PJ Hoffmaster State Park and Holland State Park.
“Hemlock like to grow along the lakeshore. So our dune ecosystem in West Michigan is very much in danger,” said Melanie Manion of Ottawa County Parks and Recreation. “Hemlock also grow along rivers and streams and provide shade for many of Michigan’s trout streams. So it’s entirely possible that if we don’t move quickly, we could see some of our best trout fisheries affected.”
HWA is native to Japan and was discovered in Virginia in 1951. The insects can be blown by the wind or transported on birds, animals, machinery or even clothing.
According to MDARD, the invasive species is believed to have arrived in Michigan on infested hemlock nursery trees that were brought in prior to, or in violation of, the state’s HWA quarantine, which was implemented in 2001. The quarantine prohibits importing hemlock trees into Michigan from areas infested with HWA.
Ageldid sucks the life from hemlocks
Less than 1/16 inch long, the insect feeds on twigs at the base of needles. They insert their long mouths into the woody shoots, sucking up moisture and nutrients. Infested trees eventually starve and die within four to 10 years. They get their name from the white, “woolly” strands of wax secreted as they feed.
Signs of infestation include:
- White, cottony masses about one-quarter the size of a cotton swab attached to the twigs, at the base of the needles, on the underside of the branches
- Needle loss and dying branches
- Gray-tinted foliage
The state’s strategy is not to eradicate infested trees, but to manage and contain the infestations.
In the very near future, MDARD will quarantine Allegan, Ottawa, Muskegon and Oceana counties. The quarantine will regulate whether hemlock trees can be moved out of or within that four-county area, Bedford said.
“Because the infestations are limited to the western parts of those four counties, we want to be sure the rest of those counties don’t become infested, too,” he said. “We learned some lessons with the emerald ash borer and are trying to stay ahead of the problem.”
Hard lessons learned from emerald ash borer
ince 2002, when it was first discovered in Michigan near Detroit, the emerald ash borer has killed tens of millions of ash trees in the state. Scientists believe it probably arrived in the United States on solid wood packing material carried in cargo ships or airplanes originating in its native Asia.
Significant investments in the fight to prevent and control invasive species have been made through the state’s departments of Environmental Quality, Natural Resources, and Agriculture and Rural Development through the Michigan Invasive Species Grant Program. Since the program began, more than $11 million has been awarded in grants to local governments, nonprofits and institutions to educate the public, manage infestations of invasive species, and research methods to control invasives.
“Michigan is committed to detecting and preventing the spread of invasive species such as the hemlock woolly adelgid,” said Joanne Foreman of the state Department of Natural Resources.
Most experts suggest that severely infested trees be cut down and destroyed. But if caught early enough, trees can be treated with systemic insecticides and other compounds sprayed or injected into the trunk or surrounding soil. While landowners can treat their own trees, officials recommend they report the infestation and then seek professional guidance from trained arborists.
In Ottawa County, Manion suggests homeowners take the risk seriously and keep an eye on their trees.
Holland’s Estelle Charroud regularly meets with her neighbors urging them to look for signs of HWA and coordinate treatment in their subdivision.
“It’s a complicated problem to tackle,” she said. “But we owe it to our children to try, we owe it to the majestic forest that surrounds our homes, and, most importantly, we owe it to the amazing wildlife for whom it is home.”
This article is part of the “Not in My Backyard” series, which is aimed to raise awareness of invasive species’ impacts in Michigan. To learn more about hemlock woolly adelgid and other invasive species, including ways you can help in this effort, visit Michigan.gov/NotInMyBackyard.
This story is provided and presented by our sponsor Michigan Department of Natural Resources.