It's not surprising that most people are not happy to see a centipede scurrying across the yard or garden. These little arthropods move very fast and look a bit alarming with their many legs and long antennae, but centipedes are actually beneficial creatures and don't usually need to be killed outdoors. If they've moved into your space and you want to get rid of them, boric acid is one of the least toxic ways of doing so.
Centipedes in Your Garden
Centipedes may move into your garden to take advantage of humid areas that have shelter for them. They often hide out under piles of wood, in leaf litter, in the crevices around fence posts, in the cracks of stone walls and similar spots. Centipedes prey on many harmful pests, such as cockroaches, flies and beetle larvae. They aren't normally a problem for people and pets, though they are venomous, and the bigger ones can deliver a painful but not dangerous bite when handled.
What Boric Acid Does
Boric acid kills many different kinds of insects, arthropods, arachnids and other pests by acting on them in two main ways. The first way occurs when they ingest it. When bugs eat boric acid, it poisons them and causes damage to their stomachs and digestive systems. This eventually causes them to die of starvation. The second way that boric acid kills pests is by damaging their exoskeletons. The rough texture of the powder nicks and scratches their protective covering. They are unable to maintain the moisture they need in their bodies, and they die of dehydration.
Applying Boric Acid
To kill centipedes, apply boric acid or a product containing boric acid in areas that centipedes frequent. The powdered form of the product is very effective against centipedes and may be dispensed from a plastic squeeze bottle. Fill crevices and wall cracks with the powder. Put powder in other areas where centipedes hide, such as cracks around hose bibs and areas under boards. If an area is too wet, the powder may lose the ability to dehydrate bugs but will still kill any centipedes that ingest it. Make sure that kids and pets can't reach the powder.
Boric Acid Precautions
While boric acid is one of the least toxic ways of killing centipedes, this doesn't mean that it is nontoxic. Boric acid must be kept away from children and pets, since eating it can cause stomach aches, nausea, diarrhea and vomiting. It can cause eye irritation, so apply it carefully, and wash your hands when you're done. Wear a dust mask while applying it to avoid inhaling any of the dust, which can cause a dry nose, mouth and throat. It may also cause nosebleeds and shortness of breath.