Hammerhead Worms: How to Get Rid of Them

You might have an invasive, alien killer on your property right now and not even know it. One that attacks under cover of night, slowly destroying the local inhabitants that make life and growth possible.

hammerhead worm on a rock

Sound like a bad bit from a cheap novel? I wish it were. I am talking about hammerhead worms.

Hammerhead worms are an invasive species that is wreaking havoc on yards and gardens across the country.

Instantly recognizable for their distinctive spade-shaped heads, eye-catching colors, and great length, these slimy creatures can grow longer than two feet.

But it is their voracious appetite for earthworms, snails, and other small animals that is doing serious damage to local ecosystems.

With no natural predators and proving frighteningly resistant to chemical and mechanical elimination, this is one tiny predator that we need to take seriously.

Fortunately, there are steps you can take to eliminate the menace of the hammerhead worm, saving both your own garden and property, and perhaps even doing your part to get rid of these things once and for all.

In this article, I’ll be sharing with you proven control and elimination methods for dealing with hammerhead worms.

Hammerhead Flatworms Are Gross and Bad

What are Hammerhead Worms?

Hammerhead worms are a type of land planarian, a land-dwelling type of flatworm that is usually found in both fresh and saltwater environments all over the world.

While there are many different species of land planarian, the most common in the United States is the hammerhead worm, scientific genus Bipalium, of which there are several species.

These creatures get their name from their flat, spade-shaped head, looking very much like a hammerhead shark crossed with a slug or snake.

This has also given rise to their common names, which include broadhead worm and arrowhead worm.

While there are many different species of hammerhead worm, they all share some common characteristics…

They are all long and thin, with a cylindrical body that can range from a few inches to upwards of one to two feet in length (though most are closer to the 6″-12″ mark).

They vary greatly in coloration, and some are even a vibrant brown-lavender color, often with darker markings or bands running lengthwise or crosswise along the body.

If you think you have spotted a hammerhead worm on your property, it is important to take action quickly, both to secure your property and to minimize its impact on the greater ecology.

These creatures breed rapidly and are difficult to eliminate once they have established themselves.

Why are Hammerhead Worms a Problem?

Hammerhead worms are a problem because they are an invasive species with no natural predators in their new environment.

But they are themselves tremendous and implacable predators in their own niche, and relentlessly pursue and eat earthworms, slugs, snails, and other creatures.

This, coupled with their high reproductive rate, means that they can quickly overrun an area and eradicate the local population of earthworms, snails, and other small critters.

While this might not sound like such a bad thing- after all, aren’t earthworms and snails considered pests by some?- the truth is that these tiny creatures play an important role in keeping our ecosystems healthy.

Earthworms help to aerate the soil and make nutrients more available to plants. Snails eat decaying plant matter, which helps to keep leaves from piling up and smothering vegetation.

When populations of these creatures are reduced, it can have a ripple effect that impacts the entire ecology.

Of more practical consideration for us, the loss of these local populations can degrade soil quality, slow replenishment of soil nutrients, impede the generation of compost, and more.

Other animals, including birds and some mammals, will have to do without their usual sources of food in the form of slugs and so forth. All of this can be laid at the feet, or rather the head, of these scummy worms.

Hammerhead worms are also difficult to eliminate once they have become established.

They are resistant to some common pesticides, and because they spend most of their time hiding during the day simply trying to find and dispatch them all is a monumental task.

The breed quickly, and a damaged part of a worm can regenerate into its own separate, adult worm!

If you think you have hammerhead worms on your property, it is best to take action sooner rather than later. The problem only gets worse the longer you wait.

Caution: Hammerhead Worms are Toxic

Before you set out on your quest for annihilation, there is one more thing you must know about hammerhead worms: they are frightfully toxic!

Their toxic secretions are used as a defense mechanism against predators, but if you get them on your skin they can cause irritation and even chemical burns.

If you or a pet were to accidentally ingest one, it can cause severe nausea, vomiting, and diarrhea. In some cases, it can even lead to death- though this is very rare.

The toxin secreted by hammerhead worms, prior to their discovery and analysis, is one that has never been seen in terrestrial animals: tetrodotoxin.

Here's how to deal with toxic hammerhead flatworms in your yard

This is the same toxin found in pufferfish and some other marine life, and it is infamously of the most potent poisons known to man. Large doses of tetrodotoxin can lead to paralysis and death if left untreated.

Mercifully, the concentrations found in hammerhead worms are small enough that they are not truly dangerous or lethal to humans but it does handily explain the total lack of their own predators.

If you are capturing or disposing of hammerhead worms, wear gloves and be sure to thoroughly wash all of you exposed skin when the job is done. Take care to keep all pets and livestock away from them.

Your Step-by-Step Plan for Eliminating Hammerhead Worms

Assuming you don’t accidentally come across one of these nasties during your usual travels or chores, you’ll need to locate them before you can do anything about them.

Easier said than done! The best time to look for them is at night, when they’re most active as they are on the hunt for prey, or after a good rain that brings earthworms to the surface.

You can use a flashlight to look for their tell-tale slimy trails, or you can keep an eye out for the damage they do: hollowed-out husks of dead snails and worms.

Look for signs of burrowing near the base of plants as well, as this might indicate a burrow. Also, look where their food is: any large concentrations of earthworms will attract them rapidly.

Once you have an idea of where they are, you can start to devise a plan of attack.

There is only one true, proven method for eliminating these hideous things: total destruction. I am not kidding.

You cannot merely step on them, cut them in half, or rely on weak poisons to kill them. The worm must be completely obliterated to make sure it won’t replicate or regenerate.

Remember when I mentioned they can reproduce if cut in half? That’s no joke. If you cut one in two with your trowel or shovel thinking the job is done you have only created two worms where there was one before.

If you step on one, the same thing can happen. Not even decapitation kills these things!

Instead, you’ll have to catch the worm and dissolve it into nothing. I wish I was kidding; that seems to be the only thing they cannot come back from.

Follow the steps below for a sure kill, then check the next section for advice on repelling them from your garden, compost pile, or property.


Before you get started, gather the following tools:

  • Jar or plastic freezer bag: You’ll use this to contain the creature.
  • Disposable gloves: I highly recommend you protect your hands while catching these things. Don’t use cloth or leather as the toxin might persist on them. Toss the gloves afterward.
  • Tweezers or forceps: Or any other tool you can use to grab the worm without touching it.
  • Chemicals: You have options here. We want something that will desiccate the worm to nothing and dissolve it entirely. Good choices include a paste of salt, boric acid, strongly soapy water, citrus oil, and concentrated vinegar.

That’s all you need. Now, let’s get to it…

Steps for Getting Rid of Hammerhead Worms Once and For All

Step 1: Catch it. This is the most difficult part. They are very good at hiding and they move quickly when they want to.

Your best bet is to grab one by the midsection with your gloved hand or forceps. Take care not to crush the worm in two.

Step 2: Deposit. Place the worm in your jar or freezer bag. If you are using a jar, ensure the lid is screwed on tightly. If you are using a bag, zip it closed and be sure it cannot get out.

Step 3: Apply chemical. Your time is up worm. Place enough of your chosen chemical agent in the container, making sure to get it all over the worm and leave it nowhere to go. It’s okay if it starts thrashing and foaming.

Step 4: Chill it. Place your container in the refrigerator to immobilize the worm and give the chemicals time to work. Check on it periodically and see if it is melting.

Step 5: Disposal. Once the worm has turned into sludge or dissolved entirely it is truly dead. Discard the evidence in the trash.

Once the worm is history you can pray that was the only one, but be warned: where there is one there is almost certainly more. Stay on the hunt and be vigilant.

Keeping Hammerhead Worms Off Your Property

There is no great trick to keeping hammerhead worms off your property since they likely arrived with a plant you purchased or else were already nearby in the area.

However, it is possible to repel them, or at least slow them down, using the same chemical mixtures outlined above for disposal, just in weaker concentrations.

The problem is that most of them, particularly salt, are also deadly to the creatures you are trying to save from these invasive monsters.

There is not much to be done about that until a specific repellant or other method is devised. It might well be better in the long run, though, to eliminate the hammerheads at any cost.

If they can be stopped before they multiply the indigenous populations can recover.

The best thing you can do is keep an eye on your garden and be vigilant in looking for these pests. If you catch them early you can nip the problem in the bud before it gets out of hand.

Try to Document Hammerheads and Report Them

This might sound a little silly, but it is a great idea to photograph and report the presence of hammerhead worms, any number, to your local and state ecological or wildlife authorities.

If they are not already aware of the problem in your area they will be, and if already aware this will help them to track its spread and might even see serious resources deployed to your property to wipe them out.

It is difficult to overstate just how destructive these worms are, and it is even more difficult to predict the long-term consequences of allowing them to go out of control.

You really do need to pull your weight in this fight; not just for yourself but for your local area and the rest of the country.

If everyone does their part, hopefully, our nation’s scientists can get a handle on the problem and find a way to get rid of these pests for good.

hammerhead worm on a rock

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