'Avoid cutting them': Invasive hammerhead worm found at St. Louis County park for first time

"Avoid cutting them … they can regenerate" is not the kind of warning most people expect to hear from a local parks and recreation department.

But that is now an official message after St. Louis County identified an invasive hammerhead worm in a green space there for the first time.

What happened?

Officials have said Cliff Cave Park in St. Louis County, Missouri, is the site of the first reported hammerhead worm sighting in a county park in the area.

According to the St. Louis County Parks and Recreation department's Facebook warning, "These flatworms, originally from Asia, can harm our local ecosystem by preying on native earthworms, which are essential for healthy soil." 

The warning also included images of the invasive worm. The organization then added that the worms are "usually seen after heavy rains; they hide under logs, rocks, and leaf litter… [and] they release toxins that can irritate the skin, and if eaten, can make people and pets sick."

These worms were reportedly found at the park along the Mississippi River, per Spectrum News. 

Why does it matter?

Earthworms help break down organic matter, improve soil structure, and support healthier ground for plants, trees, and gardens.

When an invasive predator starts targeting those native worms, it can weaken the natural systems that help keep parks and landscapes healthy. Healthy soil supports trees, backyard gardens, and broader biodiversity.

A dog sniffing through brush or a child picking up a strange-looking worm could end up having an unpleasant or even risky encounter. 

Since Cliff Cave Park is a public space, warnings about these toxic worms should affect how visitors interact with trails, leaf litter, and damp ground after storms.

What can I do?

If you find a hammerhead worm, officials have advised against touching it with bare hands and certainly don't try to chop it up, since cutting it can make the problem worse by allowing it to regenerate.

Instead, officials have told residents to euthanize the worms. They added that residents should use gloves or a shovel to put the worm into a sealed bag. 

After that, add vinegar, rubbing alcohol, salt, or soap water to the bag to kill the worm. Alternatively, freezing the sealed bag for 48 hours before trashing it will also safely euthanize it.

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