New Zealand (or Australian) Flatworms in Oregon??

Asked April 9, 2015, 11:27 AM EDT

Hello, I was reading an article: discussing worms in the garden. The article linked to a UK article about New Zealand flatworms and their taste for earthworms. I saw this play out last summer. There was a grayish (not orange) flatworm wrapped around a earthworm, who was clearly unhappy about the situation. Fascinated, I separated the two and got a very good look at the parasite. It had a flattened, vaguely triangular head and long slightly flattened body, I thought flatworm, but the intestinal parasite kind. I squashed it, unusual for me with the exception of parasites like mosquitoes as I have a very strong live and let live policy. I have yet to see another. Do we have exotic predatory flatworms in Oregon? I live in the Hillsboro area, or does it sound like something else?

Washington County Oregon

2 Responses

Wow. Thank you for your question.

From your descriptions and having done a bit of research around Ask an Expert, it looks like you have Land Planarians, or Bipalium kewense. These are native to Asia and predate earthworms. I found a blog posting from Soil Scientist Gail Langellotto noting the presence of Land Planarians in 2013 here:

The good news is that populations tend to come and go. As yet, there is no research-based information on how to get rid of them, though. My suggestion would be to keep your
earthworms happy and healthy by working lots of plant matter into your garden soil by
applying compost. That way, any predators will be feeding on the less fit population, but
you are likely to have an abundance of healthy wrigglers to do the work in your garden.

It would be very helpful to see an actual sample of the species to give a definitive diagnosis. If you see them in action again, please bring one in to our office at Public Service Building, 155 N. 1st Ave. #200, Hillsboro, 97124. Please call us at (503)821-1150 option 2 , so that we can be ready for you.

Thank you again for your question, and thank you for using Ask an Expert.

I think Land Planarians is exactly right. I looked at some additional pictures online, and although I don't remember the stripes, the color and shape are as I remember it.

If I see another, I'll be sure to capture it and bring it in.

Thanks for your response!
Amy Wachsmuth