Gophers, burrowing rodents of the species Thomomys, have powerful front legs with large claws that help them burrow under lawns, gardens and trees, leaving telltale mounds on top of the soil. They eat the roots of numerous garden plants, including the small, tender roots of young avocado trees (Persea americana). Blocking gophers with wire screens is one of several strategies for keeping them away from the roots of avocado trees, but using wire cages is not recommended.
Gopher burrows or underground tunnels are typically 2 1/2 to 3 1/2 inches wide. While their nests may be up to 6 feet deep, their feeding burrows are usually 6 to 12 inches below the surface. Gophers push dirt to the surface through short lateral systems, leaving telltale gopher mounds on the surface. Gophers use their tunnels to eat the bark of avocado roots, especially those of young trees. The tunnels protect gophers from predators, making it difficult to control them.
Wire cages, installed at planting, are used to protect the roots of flowers, shrubs and other small plants. An avocado tree grows from 30 to 60 feet tall, with roots growing as wide as the spread of its canopy. While a wire cage may protect young roots, they will also restrict their growth. As avocado trees mature, gophers are no longer attracted to their large, tough roots. To block gophers from eating the roots of smaller plants, you can make wire cages yourself using galvanized wire or buy commercial versions at a garden supply center.
A better way than wire cages to physically block gophers from chewing on young avocado roots is to install a wire barrier. University of California Statewide Integrated Pest Management Program recommends burying 3/4-inch mesh poultry wire or hardware cloth around your tree. Bury the wire at least 2 feet deep with an additional 6 inches at the bottom, bent at a 90-degree angle away from the tree and extending 1 foot above the ground to prevent gophers from going overland to get at the roots. Wire screens need to be far enough from the tree to allow the roots to grow; the drawback is that, like wire cages, they too can eventually inhibit the growth of the roots.
Other Control Methods
Several varieties of traps are sold to control gophers. You can set baited traps that pinch or choke gophers in opposite directions in the main gopher tunnel. Gophers are sometimes poisoned with grain treated with strychnine or zinc phosphide. Special anticoagulant baits kills gophers by causing them to bleed internally. Attempting to smoke gophers out of their burrows is generally ineffective because gophers quickly protect themselves by blocking their tunnels. Explosive mixtures of propane and oxygen can kill gophers by concussion and destroy their burrows but detonating explosives in gopher burrows are loud and pose dangers to users and bystanders.
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