Do ultrasonic pest repellers work?

Plug-in ultrasonic boxes promise to drive away mice, rats, cockroaches and spiders with sound you cannot hear. People who try them keep reporting the same thing: the pests carry on. Established pest guidance is built on sealing the way in, taking away food, traps and bait. Ultrasonic plugs are not how it tells you to solve the problem, and we do not recommend them either.

If you already bought a few, it is an easy mistake: the packaging is convincing and the reviews look strong. Why those reviews mislead, and what works instead, is below.

Why the reviews look so good

• Reviews come early. Many are written in the first days, before anyone knows if the problem is gone.
• Pests come and go on their own. Mice move with the weather and with food. A quiet week after plugging one in can be coincidence.
• People fix other things at the same time. They clear the cupboard, block a hole, put the bird food away. Those changes did the work, and the plug got the credit.
• You cannot hear it. So there is no way to tell whether it is doing anything at all.

Being sceptical of the reviews is sensible. Being sceptical of pest controllers is fair too. That is why most of the plan below is things you can do yourself, so nobody has to sell you anything.

Why sound is a weak plan

• It does not get where they live. High-pitched sound is blocked by walls, cupboards and furniture. Mice nest inside walls, under floors and in roof spaces, behind exactly those things.
• Animals get used to a noise that never hurts them, especially when food and shelter are right there.
• It does nothing about why they came. The gap, the food and the warmth are all still there.
• Your own pets may hear it. Pet mice, rats, hamsters and gerbils hear in the same range as wild ones, so they live with the noise too.

What works for mice and rats

1. Take away food. Dry food in closed containers, pet food put away at night, lids on bins, bird feeders away from the house.
2. Find the way in. Look for gaps around pipes, cables, vents and under doors, and for droppings and gnaw marks along walls.
3. Catch the ones inside, humanely. Live-catch traps along the walls where they run, checked at least once a day. Release according to local guidance.
4. Seal the gaps once they are out, with wire wool and filler or metal mesh, so none are shut inside.
5. Call a licensed pest or wildlife service for rats, or for anything in walls and roof spaces you cannot reach.

The mice and rats guide has the full plan. If they keep coming back, see mice keep coming back. If it turns out to be squirrels or possums overhead, see animals in the roof.

Humane only: we do not recommend poison, glue traps or anything built to injure. Glue and bucket traps explains why. Put live-catch traps and any insect bait where children and pets cannot reach them, and follow the label.

What about a cat?

A cat is a pet, not a pest plan. It cannot reach mice inside walls, and it does not close the gaps that let more in. If you want a cat, get one because you want a cat.

What works for cockroaches and spiders

For the German cockroach, the standard plan is gel bait in small dots where they hide, an insect growth regulator, and monitor traps to check progress. Follow the label on every product. Baking soda and peppermint fall in the same group as the plugs: see cockroach home remedies.

For spiders, fewer gaps and fewer insects to eat do more than any gadget. Keeping spiders out covers sealing gaps, door sweeps and outdoor lights.