‘Enemy No. 1’: Invasive aquatic plant hydrilla found in DuPage

Ask Claire Snyder about the discovery of hydrilla in DuPage County, and she doesn’t hold back.

“I am kind of calling it public aquatic plant enemy No. 1,” Snyder says.

Hydrilla turned up in a private lake in an Oak Brook subdivision on Ginger Creek, a tributary to Salt Creek. It marked only the second known occurrence of the notoriously invasive aquatic plant in the state, the Illinois Department of Natural Resources announced this week. The first time it showed up in Illinois was in Lake County in 2019.

“That population has been under control since then, and we're hoping that we can keep this infestation contained as well,” said Snyder, an IDNR natural resources specialist.

Thus far, officials have not detected any spread into Salt Creek proper, though that’s still a concern.

“Because it is in a tributary to Salt Creek that has a hydrologic connection to Salt Creek, and it flows between multiple water bodies … we're concerned that there's a high potential for spread, if it is not managed and contained, because that water body is connected to other water bodies,” Snyder explained.

“So not only could it get into Salt Creek, but it could then further flow downstream to the Des Plaines River, the Illinois River, the Mississippi River even. I really hope that that's not the case,” Snyder added, “but that is a risk in a connected system like this.”

The response

The hydrilla found in DuPage may have been unintentionally released from a homeowner’s aquarium or a water garden, IDNR reported. Hydrilla can grow up to an inch per day and form dense mats of vegetation, the agency said.

That means “it can not only outcompete native vegetation and choke off habitat for animals, but essentially you can go from a nice, beautiful open body of water to a really, just choked up plant mat very, very quickly,” Snyder said.

The hydrilla was discovered by a private lake consulting company doing routine surveys, she said.

“This year, they notified us immediately that there was a very serious nonindigenous weed, invasive weed, called hydrilla,” said Margaret Bennett, secretary of her homeowners association board, which contacted the village of Oak Brook, the county, IDNR and the DuPage River Salt Creek Workgroup.

She commended those entities for coming together to do an investigation and educate residents.

Bennett said she is “confident that this will be exterminated” next year.

Hydrilla does not grow year round and takes a break over the winter, Snyder said. The most effective treatments typically are required when the plant is actively growing. Other states that have been more actively involved in hydrilla management have found that chemical herbicide application is by far the most effective treatment, Snyder noted.

Illinois has a hydrilla task force composed of state, county, local and private organizations. The task force coordinator is with the Lake County Health Department.

“Within the last couple of weeks, the Illinois EPA went out and did some surveying of Salt Creek itself and didn't detect any hydrilla, which is encouraging,” Snyder said.

What to do

The plant looks like the native Elodea species, but hydrilla has whorls around the stem of more than three leaves with often visibly toothed edges, IDNR said.

People can limit the spread of hydrilla and other aquatic invasive species by removing all plants, animals and mud from any equipment that is used in bodies of water; draining all water from boats and gear and drying everything thoroughly with a towel or heat.

Anyone who suspects they have spotted hydrilla should notify the IDNR Aquatic Nuisance Species Program at dnr.ans@illinois.gov.

Potato-like tubers produced below the sediment surface can be viable for years, according to the Great Lakes Hydrilla Collaborative.

“We really, really do not want to become a state where hydrilla is just par for the course, and it's something we're constantly dealing with,” Snyder said. “We really want to do the very best we can, to stop it in its tracks, contain it and eradicate it from the system that it's in and ensure that we are keeping it out of the state and keeping it out of any water bodies because … it's really nefarious.”