Zinc phosphide is an acute (single-dose) rodenticide that kills within hours. When ingested, stomach acid converts it to phosphine gas, which is lethal. It's the preferred rodenticide for outdoor/agricultural use because it poses minimal secondary poisoning risk โ predators that eat poisoned rodents are unlikely to be harmed.
Rats, mice, voles, gophers, ground squirrels, prairie dogs, moles (with proper baiting). Used extensively in agriculture for field rodent control. Not commonly used indoors due to odor and formulation type.
ZP Rodent Bait (Bell Labs), ZP Gopher Bait, Prozap Zinc Phosphide, Eraze (mouse bait), many agricultural formulations. Restricted Use Pesticide in some formulations โ check state regulations.
HIGHLY TOXIC โ signal word is "Danger." Toxic to all mammals if ingested. No antidote โ treatment is supportive care only.
For gophers: Zinc phosphide gopher bait placed directly in active burrow systems is one of the most effective gopher control methods. Probe for the main tunnel, drop bait in, and close the hole. Check in 48 hours.
Bait shyness: Zinc phosphide has a strong garlic-like odor and taste. Rodents can develop "bait shyness" โ if they eat a sublethal dose and survive, they'll avoid it forever. This means proper placement and fresh bait are critical. One shot is all you get.
Pre-baiting: For rats and mice, pre-baiting with untreated grain for 2-3 days before switching to zinc phosphide bait dramatically improves acceptance. The rodents become accustomed to feeding at the location.