The key to an effective toxic baiting program is bait placement. Always place pocket gopher bait in the main underground tunnel, not the lateral tunnels. After locating the main gopher tunnel with a probe, enlarge the opening by rotating the probe or inserting a larger rod or stick. Following label directions, place the bait carefully in the opening using a spoon or other suitable implement that you use only for that purpose, taking care not to spill any onto the ground. A funnel is useful for preventing spillage.
Often, a back-filled (plugged) tunnel—one a gopher has filled with loose dirt—will feel similar to an active tunnel. Experience is required to tell the difference. New probe users might benefit from digging down to confirm that the tunnel is active or plugged. If it is an active tunnel, you can apply bait to both of the tunnel’s sides before closing it up. If it is plugged, don’t treat. Once you are comfortable with your ability to accurately determine active tunnels, you can follow the standard baiting protocols described below.
Strychnine-treated grain is the most common type of bait used for pocket gopher control. This bait generally contains 0.5% strychnine and is lethal with a single feeding. Baits containing 2.0% zinc phosphide are also available. As with strychnine, these baits are lethal after a single feeding.
Multiple feeding anticoagulants are available as well. When using anticoagulant baits, you’ll need to set out a large amount of bait—about 10 times the amount needed when using strychnine baits—so enough will be available for multiple feedings. Although generally less effective than strychnine baits, anticoagulant baits are less toxic. As such, they are preferred in areas where children and pets might be present. When using either type of bait, be sure to follow all label directions and precautions.
After placing the bait in the main tunnel, close the probe hole with sod, rocks, or some other material that excludes light while preventing dirt from falling on the bait. Several bait placements within a burrow system will increase success. Tamp down or clear existing mounds, so you can distinguish new activity. If new mounds appear more than 2 days after strychnine or zinc phosphide baiting or 7 to 10 days after using anticoagulant baits, you’ll need to rebait or try trapping.
If gophers have infested a large area, use a hand-held bait applicator to speed treatment. Bait applicators are a combination probe and bait reservoir. Once you have located a tunnel using the probe, a trigger releases a measured amount of bait into the tunnel. Generally, strychnine bait is used with such an applicator, because it dispenses only a small quantity of bait at a time.
Fumigation with smoke or gas cartridges usually isn’t effective, because gophers quickly seal off their burrow when they detect smoke or gas. However, fumigation with aluminum phosphide is effective at controlling gopher populations, although it is a restricted-use material. Applicators must be certified to use this material, which can limit homeowner use. Fortunately, many professional pest control operators have access to aluminum phosphide, so if trapping and baiting aren’t effective, consider hiring a professional.