Rodent repellents are a weak fix on their own. Ultrasonic plug-ins, peppermint oil, mothballs and predator scents do not seal the gaps rats and mice use, and they do not remove the food and shelter that drew them in. The county Vector Control Program's advice for rats focuses on sealing openings, removing food and debris and trapping. The CDC's rodent guidance does the same.
If you want rodents gone from a San Diego home, sealing, cleanup and traps do the work. Here is a look at the common repellents and where they fall short.
Ultrasonic devices
Ultrasonic repellers plug into an outlet and give off high-pitched sound that people mostly cannot hear. Angi lists them at $40 to $60. The sound does not pass through walls, furniture or boxes, so it only reaches the open part of one room. Rodents nesting in the attic, wall voids or garage storage are out of range. Even in the open, a rodent with food nearby has a strong reason to stay.
If you already own one, it does no harm, but do not count on it. Use the money on door sweeps and mesh for gaps instead.
Peppermint oil and other scents
Peppermint oil, cayenne, ammonia and plant oil sprays show up in many home remedies. Smells fade within days, and they have to be reapplied constantly. They also do nothing about the entry point. A rat that has been nesting in your attic for weeks has food, shelter and a route, and a scent at the eaves is unlikely to change that.
Strong scents can bother people and pets more than rodents, especially in small rooms.
Mothballs
Mothballs are a pesticide, and their labels limit where and how they can be used. They are made for sealed containers of clothing, not for attics, garages or engine bays. The fumes can be harmful to people and pets in enclosed spaces. Using them outside the label directions is not a fix for rodents, and it brings risks of its own.
Predator urine and decoys
Fox or coyote urine granules and plastic owls rely on fear. Rodents get used to a threat that never moves or follows through, and a plastic owl that sits in the same spot for weeks becomes part of the yard. In San Diego neighborhoods along canyons, real coyotes and owls are already nearby, and roof rats still live in the palms.
Repellent-treated tape and wire wraps
Some products for cars and outdoor equipment use bitter or spicy coatings on tape and wire wraps. These may cut down on chewing in one spot, like a section of wiring in an engine bay. They do not keep rodents out of the engine bay or the garage. If you use them, pair them with sealing the garage and checking the car. See rats in the garage and car engine.
What works instead
Three things, in this order:
- Take away food and cover: pet food, birdseed, fallen fruit, open trash, ivy and branches near the roof. The county advises trimming vegetation at least 4 feet from the roof.
- Seal the gaps: openings larger than a quarter for rats, dime-sized for mice, using mesh, hardware cloth and sealant. See how small a hole mice can fit through.
- Trap the rodents inside with snap or electric traps along their runways. See best rat and mouse traps.
Those steps match what the county and the CDC recommend, and they keep working after the scent fades. They also cost less over a year than replacing scent packs and refilling sprays every few weeks.
When people say repellents worked
Sometimes the rodents leave after a repellent goes in. Often something else changed at the same time: fruit season ended, a neighbor trapped, a gap got blocked by stored boxes, or the rodents died or moved. If the activity comes back, it is a sign the route is still open.
Why the money is better spent elsewhere
The cost of a few repellent devices or a season of scent sprays adds up. The same money buys a rodent-resistant garage door seal, a door sweep for the side door, a roll of hardware cloth for torn vent screens and a dozen snap traps. Those fix the problem in a way that lasts, and they keep working without batteries or refills.
If a provider offers repellents as the main part of a rodent plan, ask what sealing and trapping are included. A plan that leaves the gaps open will need repeat visits. See rodent control cost in San Diego for what sealing and trapping usually cost.