Among all common gopher control methods, toxic chemical baits and burrow fumigants pose the highest risks to humans, pets, and wildlife. Strychnine and aluminum phosphide stand out as the most dangerous, though for different reasons: strychnine carries extreme secondary poisoning risk to pets and wildlife, while aluminum phosphide generates a gas that can sicken or kill the person applying it. Explosive concussion devices round out the top tier of danger with their potential for burns, fires, and property damage.
Strychnine: The Highest Overall Risk
Strychnine is toxic to every animal species, including humans, and there is no antidote. It works by blocking the body’s ability to regulate muscle contraction, causing uncontrolled seizures and rigid spasms. Animals poisoned with strychnine almost always die without immediate, aggressive medical intervention. A ten-year case review published in The Canadian Veterinary Journal found that dogs were the most commonly poisoned non-target species, with 38 documented cases in western Canada alone between 2014 and 2023.
What makes strychnine uniquely dangerous is secondary poisoning. When a gopher dies from strychnine bait, any animal that eats the carcass can also be killed. The case review documented poisoning in bald eagles, hawks, coyotes, wolves, and red foxes, all species that either hunt rodents or scavenge dead ones. Preventing this chain reaction requires finding and disposing of every poisoned gopher carcass promptly, which is rarely practical in real-world conditions.
Aluminum Phosphide: Lethal Gas for Applicators
Aluminum phosphide tablets are dropped into gopher burrows, where moisture triggers a chemical reaction that releases phosphine gas. This gas kills gophers effectively (around 65% success after one treatment, rising to 81% after a second), but it also poses serious danger to the person doing the work. Toxic effects in humans can appear within 10 to 15 minutes of exposure. Early symptoms include sore throat, coughing, headache, dizziness, and nausea. At higher concentrations, exposure can escalate to heart failure, respiratory distress, seizures, coma, and death.
Some applicators have reported nausea and other symptoms of discomfort after using aluminum phosphide in gopher burrows, though other studies have found no such problems when proper protocols were followed. The U.S. EPA recommends notifying everyone within a 250-meter radius (about 820 feet) before application. The European Union requires that only trained professionals handle it, with mandatory safety measures. First responders treating victims of phosphine exposure are themselves at risk of poisoning, which underscores how readily this gas spreads.
Explosive Concussion Devices
Devices that inject a mix of propane and oxygen into gopher tunnels and then ignite it kill gophers through concussive force while also collapsing their tunnel systems. The risks to the user, however, are significant: burns, hearing damage, unintended property damage, and fire. In dry environments, a single use can spark a grass or brush fire. These devices are loud enough to be impractical in residential areas and require careful handling to avoid injury to users and bystanders. UC Integrated Pest Management specifically warns about the potential for unintended damage and injury with these tools.
Second-Generation Anticoagulant Baits
Anticoagulant rodenticides cause internal bleeding, and the second-generation versions are far more dangerous to the environment than the first. These compounds persist in soil for hundreds of days and accumulate in the bodies of animals that eat poisoned rodents. Brodifacoum, one of the most potent, takes roughly 300 days to break down in soil and has extremely high bioaccumulation potential. Difenacoum persists even longer, at 439 days. Both are classified as persistent, bioaccumulative, and toxic substances.
Because of these risks, the EPA no longer allows second-generation anticoagulants in consumer products. They’re restricted to commercial pest control operators and agricultural use, sold only in bulk containers (at least 8 to 16 pounds depending on the label). All outdoor applications above ground require tamper-resistant bait stations to reduce exposure to children, pets, and wildlife. Accidental ingestion by children is a documented concern with rodenticides in general, particularly when baits are placed in accessible locations.
Zinc Phosphide: Lower Risk Than Strychnine
Zinc phosphide is another acute toxicant used in gopher baits, but it carries substantially less secondary poisoning risk than strychnine. The USDA reports no documented cases of non-target wildlife being killed by zinc phosphide used in wildlife damage management, either through direct consumption or secondary poisoning. Research has established a low risk of secondary poisoning in cats and dogs based on the residue levels expected in treated rodents.
The primary concern with zinc phosphide is accidental exposure to pets. Dogs that eat zinc phosphide bait directly can be poisoned, and the phosphine gas released in their stomachs has sickened veterinary staff in at least four documented incidents across the U.S. There have been no reported human deaths from zinc phosphide exposure in the United States.
Carbon Monoxide Fumigation
Carbon monoxide machines pump engine exhaust into gopher burrows. While carbon monoxide is lethal to humans at sufficient concentrations (unconsciousness at 0.32% concentration within an hour, death at 0.45%), the actual risk during gopher control is low. The gas enters the burrow through a hose inserted underground, and the opening is sealed once gas is seen escaping. USDA’s wildlife services division reported zero accidental exposures of personnel or the public from gas cartridges or pressurized exhaust machines over a ten-year reporting period.
The trade-off is effectiveness. Pressurized exhaust machines achieved only about 37% gopher reduction after an initial treatment, significantly less than aluminum phosphide or trapping.
Trapping: The Lowest-Risk Effective Option
Mechanical trapping consistently ranks as the safest gopher control method across every risk category. It poses very low risk to non-target species, involves no toxic chemicals, creates no gas exposure, and requires no special licensing. After two treatment rounds, trapping achieves about 86% effectiveness, slightly outperforming even aluminum phosphide. It also gives you a direct count of how many gophers you’ve removed, so you know exactly how well it’s working. The learning curve is minimal compared to fumigation methods that require understanding soil conditions, burrow structure, and chemical handling.