Putting mothballs in your garden is illegal under federal pesticide law, and it won’t effectively repel the animals or insects you’re trying to keep out. Mothballs are registered by the EPA strictly for killing clothes moths inside sealed, airtight containers. Using them outdoors, in open air, or for any purpose not listed on the label is a federal violation, and it introduces toxic chemicals into your soil, water, and the food chain.
Why Garden Use Violates Federal Law
Every mothball product sold in the United States carries a label that reads: “It is a violation of Federal law to use this product in a manner inconsistent with its labeling.” The labeling is specific. Mothballs are approved for use in clean, airtight containers like trunks, garment bags, and storage closets to kill clothes moths and their eggs. The labels explicitly state they should not be used in containers that allow vapors to escape into occupied rooms, let alone scattered across open garden beds.
Labels also include direct warnings like “NOT FOR USE TO CONTROL SQUIRRELS, BATS AND BIRDS INSIDE THE HOME,” making it clear the product isn’t intended as a general animal repellent even indoors. Scattering them outside to deter deer, rabbits, snakes, or cats falls well outside any approved use. Improper disposal of pesticide waste, including letting mothball chemicals leach into outdoor drains or soil, is separately classified as a federal violation.
What Mothballs Do to Soil and Plants
Mothballs contain one of two active chemicals: naphthalene or paradichlorobenzene (sometimes labeled as PDB). Both work by releasing toxic vapors in an enclosed space. Outdoors, those vapors dissipate quickly in open air, which is one reason mothballs are ineffective as garden pest control. But the solid mothball itself sits in the soil and slowly breaks down, contaminating the ground around it.
Naphthalene binds to soil particles and can be absorbed directly by plant roots. It also deposits on plant leaves from the air. In soil, naphthalene has a half-life that can exceed 80 days, meaning it takes nearly three months for just half of the chemical to break down. Bacteria, fungi, and sunlight all contribute to degradation, but the process is slow, especially in deeper or shaded soil where airflow and UV exposure are limited. During that time, the chemical sits in the root zone of anything you’re growing.
If you’re using mothballs near a vegetable garden, herb bed, or fruit plants, the chemicals can enter the food you eat. Even in ornamental beds, the contamination disrupts the soil ecosystem that healthy plants depend on. Naphthalene is moderately toxic to aquatic life, including fish and water fleas, so rain washing it into storm drains or nearby waterways creates broader environmental harm.
Risks to Pets and Wildlife
Mothballs scattered in a garden are accessible to dogs, cats, birds, and wildlife. Ingestion is the most common route of exposure, but animals can also absorb the chemicals through their skin or by breathing the vapors. All animals are vulnerable, though cats are suspected to be more sensitive than other species.
Naphthalene irritates the digestive tract, so vomiting, loss of appetite, and abdominal pain typically appear first. Larger exposures can destroy red blood cells, causing anemia, pale gums, and difficulty breathing. In rare cases, neurological symptoms like tremors, loss of coordination, and seizures develop. Paradichlorobenzene causes similar digestive distress, along with lethargy and trembling. Chronic or repeated ingestion of PDB can damage the liver and kidneys.
A single mothball is enough to poison a small dog or cat. The white, round shape can resemble a treat or toy, and the waxy texture doesn’t deter chewing. Wildlife faces the same risk. Birds, which the EPA specifically warns against targeting, can pick up mothballs or ingest contaminated insects from treated soil.
Risks to Children
Mothballs look like candy or small toys to young children. A child playing in a garden where mothballs have been placed can easily pick one up and put it in their mouth. Naphthalene exposure in children can cause the same red blood cell destruction seen in animals, and children with a common inherited enzyme deficiency (affecting roughly 400 million people worldwide) are especially vulnerable to severe reactions. Even handling mothballs and then touching their eyes or mouth exposes children to the chemicals through skin absorption.
Why Mothballs Don’t Work Outdoors
The entire mechanism of mothballs depends on vapor building up in an enclosed space until it reaches concentrations toxic enough to kill moths. In a garden, wind and open air prevent vapors from ever reaching effective levels. Animals passing through a garden bed encounter a faint odor at most. Some may avoid the smell briefly, but there is no evidence that mothballs reliably repel deer, rabbits, squirrels, moles, snakes, or any other common garden pest in outdoor conditions.
The smell fades quickly as the chemicals evaporate into the atmosphere, so even the brief deterrent effect disappears within days. You’d need to constantly replace them, compounding the soil contamination and legal issues with each application.
What to Use Instead
Effective, legal garden pest control depends on which animal you’re dealing with. Physical barriers are the most reliable option for most situations.
- Fencing and netting: Hardware cloth keeps burrowing animals out of raised beds. Bird netting protects fruit. Deer fencing needs to be at least 8 feet tall to be effective, though shorter angled fencing can also work.
- Motion-activated deterrents: Sprinklers or ultrasonic devices triggered by movement can discourage deer, rabbits, and cats without chemicals.
- Scent-based repellents: Products specifically registered for outdoor garden use (check the label) are available for deer and rabbits. These use ingredients like putrescent egg solids or capsaicin and are designed to be reapplied after rain.
- Companion planting: Strong-smelling herbs like rosemary, lavender, and mint can discourage some insects and browsing animals when planted as borders, though results vary.
- Row covers: Lightweight fabric draped over crops blocks insects while allowing light and water through, eliminating the need for chemical pest control entirely.
For persistent problems with specific animals like moles, voles, or groundhogs, trapping or professionally applied repellents are more effective and legal alternatives. Your local cooperative extension office can recommend approaches tailored to the exact pest and region you’re dealing with.