ALUMINUM PHOSPHIDE
The EPA allows the use of both aluminum phosphide and carbon monoxide (gas cartridges or PERC machine) for the fumigation of prairie dogs. We recommend using aluminum phosphide in most locations, although gas cartridges are necessary in some. We will apply gas cartridges to all burrows if the customer desires.
ALUMINUM PHOSPHIDE. Aluminum phosphide is both very effective for removing prairie dogs and fairly safe for people, pets, or livestock in the area. When compared to other pesticides, aluminum phosphide is safer in the larger environment with very little to no risk to anything outside of the sealed prairie dog burrows.
Aluminum phosphide tablets are dispensed into each prairie dog burrow. The Aluminum phosphide reacts with moisture in the ground or atmosphere to liberate phosphine gas. Phosphine is a colorless and odorless gas, which, once inhaled, creates symptoms similar to carbon monoxide. The affected animal dies by suffocation.
Though phosphine is slightly heavier than air, we do seal the treated burrows to keep the gas underground and to help prevent prairie dogs from escaping. Given the time-release aspect of the fumigant tablets, the phosphine gas may remain in the burrow for up to ten days, though 3 to 4 days is more likely.
CARBON MONOXIDE
Carbon monoxide causes death by tying up the oxygen transport in the body, leading to asphyxiation. There are two options for administering carbon monoxide.
With gas cartridges, sodium nitrate and charcoal are ignited and produce a large, but short-lived, cloud of carbon monoxide and carbon dioxide smoke inside the burrow. The cloud of carbon monoxide has an odor and is visible, making it safer than phosphine when working around occupied buildings. In the slight chance that the gas gets inside a building, it will be detectable and the building should be evacuated and vented. Due to its extra safety, we must use gas cartridges on any burrows within 100 feet of any occupied, or potentially occupied, structure.
The cloud of gas from a gas cartridge lasts for only an hour or two at best in the burrow. Gas cartridges are very safe for people, pets, livestock, and other wildlife but have a lower effectiveness rate than aluminum phosphide. Gas cartridges are more expensive to purchase and apply.
Carbon monoxide can also be applied with the use of a PERC® (pressurized exhaust rodent controller) machine. Carbon monoxide is generated by a gasoline engine, cooled and stored in a tank before being introduced to the burrows by hose and wand. The burrows are sealed in the process. As the carbon monoxide from a PERC machine has no color or odor, the State of Colorado recommends that this method not be used within 150 feet of an occupied structure. We do not currently use a PERC machine but may in the future.