Wisconsin officials are on high alert as an invasive species could threaten millions of trees in the state. The hemlock woolly adelgid, a tiny yet deadly non-native species, has the Wisconsin Department of Natural Resources and the Department of Agriculture, Trade and Consumer Protection sounding the alarm.

What's happening?

Wisconsin Public Radio reported that a highly invasive "aphid-like" species known as the hemlock woolly adelgid has been spotted four times since 2017 in Wisconsin tree nurseries. These sightings have state regulators warning that the species is "knocking at [Wisconsin's] doors."

Experts are also concerned because next door in Michigan, the invasive species has already "become established in 11 counties." Since the insects are tiny — only millimeters long — they can be challenging to detect. What's worse, hemlock woolly adelgids spread fast, with one egg sac containing up to 300 eggs. 

WPR noted that already the invasive insects have "killed millions of trees in the eastern U.S. and threaten 80 million eastern hemlock trees in Wisconsin." Native to Asia, hemlock woolly adelgids have the potential to wipe out forest ecosystems by feeding on native hemlock trees. 

"Once it infests hemlock, without any intervention, it's going to kill the trees," DATCP's forest pest unit supervisor Michael Falk told WPR. "It's just not something anyone would want to happen here in Wisconsin."

Why is the threat of hemlock woolly adelgids important?

Invasive species, such as the hemlock woolly adelgid, compete with native species for resources, overtaking entire landscapes. In this case, the invasive insects pose a serious threat to the local environment, as they can destroy entire swaths of hemlock trees in Wisconsin. The loss of these trees would be catastrophic for the forest ecosystem, as other organisms rely on hemlock trees for food and shelter. 

According to WPR, hemlock trees also play a crucial role in supporting local streams by keeping these waterways "cool and clean."

What's being done about the invasive species?

State agencies are being proactive, tracking the invasive species to monitor its spread. Come springtime, DNR and DATCP will place 3D-printed traps at 30 sites to catch insects and later analyze the species.

"We're going to be looking at about 30 sites … for this insect to make sure it's not out on the landscape somewhere where we don't know about it," DNR's invasive forest pest coordinator Mike Hillstrom told WPR.

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