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AUBURN UNIVERSITY, Ala. — Last year, the gardening world was set ablaze with the hot topic of the hammerhead worm—an invasive flatworm. With the arrival of spring temperatures, Alabama Cooperative Extension System professionals say these worms are back and here to stay.

Key Characteristics

Meredith Shrader, an Alabama Extension entomology diagnostician, said although the hammerhead worm was a hot topic last year, they have been around for a while.

“While this pest is new to some, it has been in the United States since the early 1900s, when it was accidentally introduced from imported horticultural plants,” Shrader said.

As its name suggests, the most prominent feature of the hammerhead worm is the hammer-like shape of its head. This worm is also much larger than other worms homeowners may be familiar with. Its body can be as long as 15 inches but is more commonly between 8 and 12 inches. Also, this worm can have between one and five dorsal stripes on its body. With their predatory and cannibalistic nature, hammerhead worms’ prey mainly consists of other annelids, such as the common earthworm.

“Hammerhead worms thrive in hot, humid environments,” Shrader said. “In Alabama, this spring has been perfect for these worms and is likely the reason many homeowners are seeing them out and about. The recent rains and warmer temperatures have enticed them to wander into gardens and yards in search of prey.”

Their Environment

The places in which you may find hammerhead worms can change depending on the weather. Some of their favorite hiding spots include in leaf litter or under rocks, logs or shrubs. Because they thrive in humid places, moisture is an important factor to them.

“If there is adequate moisture, we will continue to see hammerhead worms,” Shrader said. “However, if temperatures rise and the amount rainfall decreases, populations will crash, and the worms will become more elusive in our environment.”

According to Shrader, greenhouse environments offer these worms favorable conditions, so they may be found in those environments year-round.

Control Options

Because they feed on beneficial and native garden creatures, knowing how to control hammerhead worms is key for Alabama gardeners. Katelyn Kesheimer, an Alabama Extension entomologist, said it is important to realize that these worms reproduce asexually.

“Because they reproduce asexually, if you try to get rid of them by cutting them in half, you will only make more worms,” Kesheimer said. “Also, they possess a toxin, and we don’t have information on how harmful it is to humans, so I would avoid touching the worms if possible.”

There are several control options for hammerhead worm infestations. These include putting them in soapy water that they can’t crawl out of and crushing them to the point where there are no viable segments.

“Other home remedies include spraying them with vinegar, as well as dumping salt on them like you would with slugs,” Shrader said. “These are quick-fix options if you only have a couple in your yard. However, if you apply large amounts of salt or vinegar to the landscape, it may harm vegetation.”

Also, amphibians will eat hammerhead worms, so they may help keep population levels low.

Reporting Hammerhead Worms Unnecessary

While hammerhead worms are considered invasive species, there is no reporting system in place through the Alabama Department of Agriculture and Industries or any other agency in Alabama.

“If you find them in your yard, you can rid them from your yard using the techniques described above,” Shrader said. “However, their presence does not need to be reported to Alabama Extension or any other agency.”

More Information

For more information about other gardening and landscaping topics, visit the Lawn & Garden section of the Alabama Extension website, www.aces.edu.