We’ve said it before and we’ll say it again: there are no bad plants or animals, just plants or animals living in the wrong place. Hammerhead worms—members of the genus Bipalium—are flatworms native to Asia. Gradually introduced to North America via imported plants, several hammerhead worm species have become established in the US and Canada. This is a problem because as predatory invasive species, Bipalium feed on native species and disrupt local ecosystems. This has some implications for our gardens, as well, so let’s dig in and learn a bit more about hammerhead worms and what to do if you find one.
Different Species of Hammerhead Worms
There are four different species of invasive hammerhead worms we need to worry about. All are members of the genus Bipalium, meaning that they’re all planarians or “true” flatworms with flat worm-like bodies and distinctive hammer-shaped heads. The four species found in North America are:
· Bipalium adventitium
· Bipalium kewense
· Bipalium pennsylvanicum
· Bipalium vagum
Of the four, B. kewense seems to have the most widespread impact. It was first identified in the US back in 1901, when it was found in a greenhouse containing exotic plants. From there, it’s spread across swaths of the US and Canada, where it causes big problems for some ecosystems and for agriculture.
Problems Caused by Invasive Hammerhead Worms
You may be wondering what the issue is—there are lots of worms and flatworms in North America, so what difference do a few more make? Well, the fact that we have so many species of earthworms, both native and invasive, is the issue. As many gardeners know, earthworms are great for soil health, converting organic matter into nutrition plants can use and thus naturally fertilizing soil. Many gardeners and homesteaders raise their own worms or add them to compost heaps to help create natural soil amendments and help their plants grown. Hammerhead worms aren’t true worms; as a matter of fact they’re worm predators that feed on earthworms including night-crawlers. This harms earthworm populations and can cause big problems for ecosystems and agriculture that depend on them.
Hammerhead worms are also toxic, in that they produce a neurotoxin called tetrodotoxin which helps them subdue and consume their prey. This generally isn’t particularly dangerous to humans, but if you encounter a hammerhead worm avoid letting the mucus they produce contact your mouth, eyes, or other delicate tissues. This goes for pets and children as well. If you, another person, or your pet come into that kind of contact with a flatworm and start to have a reaction, contact a relevant medical professional.
Dealing With Hammerhead Worms In the Garden
So what should you do if you find hammerhead worms in your garden? Well, step one is don’t panic—hammerhead worms have been here for a while and for good or ill we’re learning to live with them. The best thing to do is to carefully dispose of the hammerhead worms you find. Wear gloves when handling them, due to the aforementioned neurotoxins. Likewise, keep them away from pets and children. Capture the worms and place them in an escape-proof container like a plastic bag, jar, or bottle and then kill the worm using one of the following methods:
· Place the container in the direct sun for several hours.
· Sprinkle some table salt in the container.
· Squirt some hand sanitizer in the container.
· Place the container in a freezer.
· Put soapy water in the container.
When the hammerhead worm has been dispatched, dispose of the sealed container in the trash—don’t try to compost it or otherwise return it to the soil. That can allow eggs within the dead worm to hatch and start the cycle all over again. Carefully dispose of or clean your gloves and then thoroughly wash your hands, too.
Hammerhead worms have been around for a while, and learning to manage them is an important skill should you find them in your garden. The best approach is to spend time with your soil, your compost, and your plants, keep an eye out for hammerhead worms, and deal with them when they appear in a prompt and effective manner. Again, there are no bad plants or animals, but these critters are definitely in the wrong place and we need to respond accordingly.
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