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These creatures are living in my lawn. They seem to appear only during the summer, for the last three years. I think they’re killing the grass, perhaps by chewing on the roots. Or, at least, the grass looks sick and brown where these things are most numerous.

So, my questions are …

  1. What are they
  2. Do you think they are, in fact, hurting the grass
  3. How do I kill them
  4. Can I prevent a re-occurrence of the annual infestation.

If it helps, I live in Okinawa, which has a tropical climate somewhat like Hawaii.

Edit: My local garden/agri center folks didn’t seem to recognize them, but recommended spraying with Trebon (etofenprox). This seems to be an insect killer, and these creatures are clearly not insects.

  • Your nursery doesn't recognize caterpillars? Grubs (which they aren't) are sickly white, live under turf, and destroy roots. Caterpillars bite leaves like Japanese Beatles do. Trebon? The EPA are not fans: Highly toxic to bees exposed to direct treatment on blooming crops or weeds. Do not apply product while bees are active. I'd use liquid dish soap or organic shampoo. Commented Jul 24, 2023 at 19:53

1 Answer 1


Caterpillars are insects, they are insect larvae. Consequently, insecticides will kill them.

It looks like they are called lawn caterpillars (there seem to be 4 varieties that can attack lawn).

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Lawn caterpillars, the term used to group together fall armyworms, grass loopers, and sod webworms, can prove devastating to plants. August through October usually holds the largest problems for lawn caterpillars, but more frequent rains can lead to higher than normal populations. Fall armyworms range in color from green to brown and have both light and dark stripes running the entire length of their bodies. ..
How to Control Lawn Caterpillars For controlling these pests, there are a number of techniques that homeowners can use. One method is to control the growth of the grass itself. Reducing the use of high-nitrogen, quick release fertilizers. These fertilizers promote the quick top growth, which is what the caterpillars like to feed on. Another way to reduce the caterpillars is to bag grass clippings as soon as the lawn has been mowed, these lawn caterpillars lay their eggs on the grass blades, and continue mowing the lawn at a normal height.

Image and Text from How to Get Rid of Lawn Caterpillars. There are additional chemical methods discussed there, but I dont want to plagiarize the whole article.

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