Pest Control
How to Get Rid of Groundhogs: Fencing, Repellents & Traps
The True Cost of Groundhog Damage
Groundhogs (Marmota monax), also known as woodchucks, are formidable landscape pests. A single adult consumes up to two pounds of vegetation daily and excavates burrows that can extend 30 feet horizontally and 5 feet deep. This subterranean network undermines retaining walls, sheds, and home foundations, creating severe structural hazards alongside the destruction of your garden crops. According to the Penn State Extension, groundhog damage accounts for millions of dollars in agricultural and residential losses annually. Eradicating them requires a multi-tiered approach targeting their digging instincts, foraging habits, and shelter requirements.
Physical Exclusion: The L-Header Fence Method
Standard vertical fences fail against groundhogs because they are both adept climbers and relentless diggers. The only proven physical barrier is the L-header fence, which exploits their instinct to dig straight down rather than backward when encountering an obstacle.
Materials and Specifications
- Wire: 14-gauge or 16-gauge galvanized welded wire with a 2-inch by 4-inch mesh.
- Height: Minimum 3 feet above ground.
- Posts: T-posts or 4x4 wooden posts spaced no more than 8 feet apart.
Installation Protocol
- Dig a trench 12 inches deep and 12 inches wide along the perimeter of the area you wish to protect.
- Attach the wire to the posts, ensuring the bottom 12 inches extends into the trench.
- Bend the bottom 12 inches of the wire at a 90-degree angle so it forms an 'L' shape, with the flange pointing away from the garden (outward).
- Bury the outward-facing flange in the trench and cover with compacted soil and sod.
- Leave the top 6 inches of the fence unattached to the posts, flopping outward at a 45-degree angle. This prevents them from climbing over, as their weight will pull the floppy wire down.
Chemical and Natural Repellents: Efficacy Matrix
Repellents are a secondary line of defense, best used to protect specific ornamental plants or to discourage initial exploration before a burrow is established. They are rarely effective once a groundhog has established a primary food source. Below is a breakdown of active ingredients based on data from the Internet Center for Wildlife Damage Management.
| Active Ingredient | Product Example | Application Rate | Rainfastness | Best Use Case |
|---|---|---|---|---|
| Capsaicin (Hot Pepper) | Miller Hot Sauce | 1 tbsp per gallon of water | Low (washes off easily) | Perimeter spray on non-edible ornamentals |
| Thiram (Fungicide) | Liquid Fence Deer & Rabbit | 1 qt per 100 sq ft | Medium | Edible crops (strictly observe harvest intervals) |
| Predator Urine (Coyote) | Shake-Away Granules | 1-2 oz per 10 linear ft | Low | Burrow entrance deterrence and boundary marking |
| Putrescent Egg Solids | Deer Off | 1 oz per gallon | High (contains binder) | Long-term foliar application on shrubs and low branches |
Pro Tip: When applying capsaicin-based sprays, always add a surfactant (like a few drops of dish soap) to the mixture. Groundhog fur and plant leaves have waxy cuticles that repel water-based sprays; the surfactant breaks the surface tension, ensuring the repellent adheres and dries properly.
Live Trapping and Relocation Protocols
When exclusion and repellents fail, live trapping becomes necessary. The industry standard for adult groundhogs is the Havahart 1081 (10x12x32 inches) or the Trap Ease Extra Large. Smaller traps will result in tail-catches or bent doors when the animal panics.
The Bait Trail Strategy
Groundhogs are naturally neophobic (fearful of new objects). Placing a trap directly over a burrow entrance will result in the animal simply digging a new exit. Instead, use the bait trail method:
- Place the trap 3 to 5 feet away from the primary burrow entrance.
- Leave both trap doors open and tie them up with zip ties for the first 48 hours. This allows the groundhog to walk through and build confidence.
- Scatter a trail of sunflower seeds or sweet corn leading into the trap.
- Place the primary bait—fresh cantaloupe chunks or strawberries—at the very back of the trap, past the trigger pan.
- After 48 hours, remove the zip ties, arm the trap, and cover the top and sides with a burlap sack. The darkness reduces visual stimuli, keeping the trapped animal calm and preventing injury.
Legal Warning: According to The Humane Society of the United States and various state wildlife agencies, relocating trapped groundhogs across county lines or into public lands is strictly illegal in many jurisdictions (including NY, PA, and MA). Groundhogs are primary vectors for rabies and tularemia. In most states, you are legally required to either release the animal on the exact property where it was trapped or humanely euthanize it. Always consult your local Department of Natural Resources before moving a trap.
Burrow Fumigation: The Giant Destroyer Method
If trapping is unfeasible, burrow fumigation using sulfur-based smoke cartridges (such as the Giant Destroyer) is highly effective, provided it is done in the spring when young are in the den or during early morning hours when adults are resting.
Step-by-Step Fumigation
- Locate all exits: Groundhog burrows typically have 2 to 5 entrance/exit holes, often marked by distinct mounds of excavated soil.
- Seal secondary holes: Stuff all but the main entrance with crumpled newspaper and cover with 6 inches of dirt. Do not use loose, dry soil, as smoke will escape through the air gaps.
- Wet the soil: Water the ground heavily around the main entrance. Moist soil compacts tightly and prevents smoke from leaking to the surface.
- Deploy the cartridge: Light the Giant Destroyer fuse, allow it to smoke heavily for 10 seconds, and drop it into the open hole.
- Seal immediately: Cover the main entrance with a piece of sod or a heavy clump of wet mud to trap the carbon monoxide and sulfur dioxide inside the tunnel system.
Groundhog Deterrence Decision Matrix
Choosing the right intervention depends on your property layout and the severity of the infestation. Use this framework to dictate your strategy:
- Scenario A: High-value vegetable garden, active chewing damage.
Action: Install an L-header fence immediately. Apply Thiram-based repellents to the outer perimeter while the fence is being constructed. - Scenario B: Burrows located under a shed, deck, or concrete porch.
Action: Do not use smoke bombs (fire hazard and structural risk). Install a one-way exclusion door over the main entrance. Leave it for 5 days to ensure all animals exit, then remove the door and permanently seal the opening with 1/2-inch hardware cloth buried 12 inches deep. - Scenario C: Large rural property with scattered, distant burrows.
Action: Fencing is cost-prohibitive. Utilize Giant Destroyer fumigation in early spring, followed by filling the collapsed tunnels with gravel and topsoil to prevent re-habitation by skunks or foxes.
Frequently Asked Questions
Will mothballs keep groundhogs away?
No. Mothballs (naphthalene or paradichlorobenzene) are entirely ineffective outdoors. The gas dissipates rapidly in open air and soil, and using them in a manner not specified by the label is a violation of federal pesticide law. They also pose severe toxicity risks to household pets and local groundwater.
How deep do I need to bury chicken wire to stop them?
Chicken wire (poultry netting) is not recommended because groundhogs can easily chew through the thin, flexible metal. Always use 14-gauge or 16-gauge galvanized welded wire, buried at least 12 inches deep with an outward-facing L-flange.
What time of day are groundhogs most active?
Groundhogs are diurnal, meaning they are active during the day. Their peak foraging hours are early morning (6:00 AM to 9:00 AM) and late afternoon (4:00 PM to 7:00 PM). Set and check your traps during midday when they are typically resting in their burrows to avoid catching non-target species like opossums or stray cats.
