If you find a couple of pocket gopher mounds in an alfalfa field, set traps before the rodents get out of hand, recommends Roger Baldwin, University of California Cooperative Extension wildlife pest management advisor for the Statewide IPM Program.
Baldwin has researched various gopher control methods, and of the primary three – baiting, fumigation and trapping – trapping and fumigation with aluminum phosphide were the most effective and least expensive. “Trapping is more practical and more readily available in many situations, however, because the use of aluminum phosphide for burrow fumigation is restricted,” he says.
If you’re looking for new traps, he recommends trying the Gophinator. It won in comparison trials with the old standard, the Macabee. “It works better primarily because we caught larger gophers at a higher rate. It is a more powerful trap when sprung; it has a lot of force behind it.”
Before setting traps in pests’ tunnel systems, determine if you’re hosting pocket gophers or moles. Gophers cause “significant damage” in alfalfa – a crop they love to consume. Moles, however, eat primarily grubs, worms and insects. “They’re not causing a lot of damage to alfalfa in most cases.”
Gopher mounds are horseshoe-shaped, with plugs laying toward their lower ends. Mole mounds are more circular and volcano-like; plugs are in the middle of mounds or not visible.
Peanut butter and other attractants don’t help, Baldwin says. He studied several and found unbaited traps work as well as baited.
Use a long screwdriver to probe and find a gopher’s tunnel system, he recommends. “What we are looking for is a drop in the probe to indicate a vacant spot. And that vacant spot should, theoretically, be a gopher tunnel. Then it’s time to dig down to that tunnel system.”
Some people use shovels or spades, but he uses a Japanese gardening tool called a Hori-Hori knife, which allows him to stay on his knees from start to finish.
“The knife has a serrated edge and cuts through vegetation really easily.” It’s also the right length and width to open a tunnel enough to place a trap into it.
“It’s important to clean a tunnel out,” Baldwin says. “Gophers don’t like open tunnel systems; they want to plug them. If you leave a lot of loose dirt, a gopher will start shoving that dirt in front of it, and there’s a good chance it’s going to set that trap off before it ever gets into it.”
After setting the trap, using gloves for protection, place it deeply into the tunnel, lying flat so it won’t move when a gopher walks on it. Then stake down and mark the trap’s location with a flag.
Baldwin also suggests not covering the holes. “We found there are few added benefits to covering traps. And if you check traps the next day, you save having to uncover them.”
Setting one trap per gopher burrow system may not be enough. Tunnels can go in as many as five or six directions, although most go in one or two. “Set as many traps as you have directions, because you don’t know where in that tunnel system the gopher is.”
Trapping can be economical in an 80-acre field with a fair amount of gophers, Baldwin believes. “You can catch a lot of gophers in a relatively short time. Once you get good at this, you can put out 10-15 traps an hour. If you have a lot of gophers, you’ll probably have a 60%, 70% or 80% capture-success rate. With baiting, results are often much lower, although success has varied widely across localities.”
Or, he says, use traps after utilizing a burrow builder that deposits bait in artificial burrows.