Mothballs do not get rid of possums. They are ineffective as a wildlife repellent, and using them outdoors for this purpose is actually illegal under federal pesticide law. The active chemicals in mothballs were designed to kill fabric pests like clothes moths in enclosed containers, not to deter animals in open-air environments where the fumes disperse quickly.
Why Mothballs Don’t Work on Possums
Mothballs contain either naphthalene or paradichlorobenzene, chemicals that release fumes toxic to small insects in sealed spaces like garment bags or storage trunks. Outdoors, those fumes dilute rapidly in open air and never reach a concentration strong enough to bother a possum. The Louisiana Department of Health states plainly that mothballs are “ineffective for this use” when placed outside to repel wildlife, including rodents, squirrels, bats, and snakes. Possums are no exception.
You might see possums walk right past a pile of mothballs without reacting. Their motivation to find food, water, or shelter easily overrides any mild irritation from a fading chemical odor.
Outdoor Mothball Use Is Illegal
Mothballs are regulated as pesticides by the Environmental Protection Agency. Every mothball package includes a label specifying exactly where and how the product can legally be used. Scattering them in your yard, under a porch, or around a garden is not on that label. The National Pesticide Information Center confirms that using mothballs in a way not specified by the label is illegal and can harm people, pets, and the environment.
This isn’t a technicality. Mothballs placed outdoors contaminate soil, plants, and water. The chemicals don’t just evaporate harmlessly. They leach into the ground and can persist in the environment, creating a hazard long after the possums have ignored them and moved on.
Health Risks to Your Family and Pets
If you can smell mothballs, you’re breathing in their chemicals. Symptoms of exposure include headaches, nausea, eye and nose irritation, and coughing. For children and pets, the risks are worse. Mothball fumes are heavier than air and settle along the ground, right where small children crawl and pets spend their time. Kids and animals sometimes mistake mothballs for candy or food and eat them, which can cause serious poisoning.
Longer-term exposure to naphthalene can cause a condition called hemolytic anemia, where red blood cells break down faster than the body can replace them. Naphthalene is also classified as a possible carcinogen. Extended contact has been linked to liver and kidney damage. Spreading mothballs around your property to deal with a possum problem trades a minor nuisance for a genuine health risk.
What Actually Keeps Possums Away
Possums are opportunists. They show up because your property offers something they want: food, shelter, or both. The most reliable approach is removing those attractions and physically blocking access to your home.
Remove Food Sources
Pick up fallen fruit from trees and shrubs. Bring pet food dishes inside at night. Cover trash and garbage bins with tight lids, and secure compost piles in containers that lock. If you have bird feeders, modify them or clean up spilled seed so food doesn’t accumulate on the ground. A yard with nothing to eat is a yard possums pass through instead of settling into.
Eliminate Shelter Options
Clear brush piles, woodpiles, and dense ground cover where possums like to hide during the day. Plug any open burrows on your property. The less cover your yard provides, the less attractive it is as a home base.
Seal Entry Points on Your Home
This is the most important step if possums are getting under your porch, into your crawlspace, or inside your walls. Secure crawl spaces, porches, and decks with galvanized hardware cloth (1 by ½ inch mesh). Bury the mesh at least 2 inches below ground and extend a 12 to 18 inch horizontal skirt under the soil to prevent digging. Cover vents with metal vent covers, and use metal flashing or hardware cloth to protect any openings that need to stay open for airflow.
Plug gaps along your foundation. Trim tree branches that touch or overhang your roof, since possums are good climbers. Wrapping the bottom two feet of a tree trunk with metal flashing prevents them from climbing up in the first place.
If a possum is already living under your structure, a one-way door lets it leave but not return. Install one over the main entry point after sealing all others. A piece of crumpled newspaper propped in the door helps you confirm when the animal has exited, since the paper will be displaced.
Fencing
A standard fence won’t stop a possum, but adding a tightly stretched electric wire near the top, about 3 inches out from the mesh, prevents climbing. Strips of stainless steel porcupine wire along the top of a fence serve the same purpose without electricity.
Possums Are Less Dangerous Than You Think
Many people want possums gone because they assume the animals carry rabies or other serious diseases. In reality, possums account for less than 1% of rabies cases reported to the CDC. Their body temperature runs between 94 and 97 degrees Fahrenheit, which is too low for the rabies virus to replicate effectively. The virus needs a host body temperature closer to 100 to 102 degrees.
The hissing, drooling, open-mouth display that looks alarming is a bluff, not a sign of illness. It’s a defense mechanism, and a possum doing this is far more scared of you than you are of it. Possums also eat large quantities of ticks, helping reduce tick-borne disease in your area. Before going to great lengths to remove one, it’s worth considering whether it’s actually causing a problem or just passing through.