Managing Pocket Gophers and Voles in Blueberry Fields
Pocket gophers can cause damage to blueberry plantings. These animals dig extensive tunnels or runways which may extend as far as 800 feet and cover an acre of land. Since they feed on plant root systems, extensive damage can occur before symptoms are evident above the ground. Gophers are seldom seen since almost their entire lives are spent underground.
Pocket gophers are active throughout the year. Breeding generally begins in the early spring. After the young have grown they are forced from the burrow where they migrate, sometimes above the ground, to new uninhabited areas.
Pocket gopher activity is more evident in the spring and fall when new burrow systems are excavated and the loose soil pushed above the ground. During the remainder of the year some new mounds may appear but the majority of the animal activity goes unnoticed.
Most people have found that direct control strategies are easier and more effective in the fall, when the gophers are the most active, less effective in the spring, and practically useless in the winter and summer when their burrow systems are harder to find.
Pocket gophers can often be excluded from small areas by building barriers, generally 3 feet deep or more, around the perimeter of a planting. Barriers should be solid obstacles, either concrete or wire, that the animal cannot dig or chew through. This may not be practical for large plantings.
Changing the gophers’ living conditions, by either reducing or eliminating their source of food, has the most profound and long-lasting effect. When a food source is eliminated, animals have two options: either move or die.
Eliminating a food source, such as grass or weed strips between plantings can, however, have unwanted effects. Existing gophers are forced to the remaining food source the blueberry roots.
When indirect management strategies are not feasible, or where damage cannot be tolerated, traps, fumigants (gases), and toxicants (poisons) can be effectively used.
Trapping is most effective with small populations of gophers. Use traps in autumn or spring. Autumn is usually the best time to trap because gophers are most active. Traps should be set at freshly worked tunnels. Regular steel-jawed traps (size 0 or 1) can be used. Several types of gopher traps may be purchased at most hardware stores, including specially designed traps that kill the gophers. Success depends upon the proper use of the traps. See Extension Bulletin 1404, Pocket gopher control, or Extension Circular 1117, Controlling pocket gopher damage to agricultural crops (see Bibliography).
Fumigants or gases can be used with small to medium-sized populations. Most are effective in wet heavy soils where the gases remain in the burrow system to asphyxiate or suffocate the animals. None are recommended for light sandy or dry soils where the gases rapidly dissipate out of the tunnels. Several types of fumigants can be used. Contact your local county Extension office for more information.
Toxicants or poisons used to hand or mechanically bait gophers are also available. Contact your local county Extension office for those registered.
Voles, also called meadow mice, short-tailed mice, or orchard mice, are very similar to pocket gophers because they live much of their life below ground. Like gophers, a large percentage of their diet consists of roots. Unlike pocket gophers, they feed above the ground as well.
The first signs of vole activity are 1 to one and one-half inch open holes in the ground with connecting compacted paths. Because voles confine most of their above-ground feeding to these paths, clipped vegetation can generally be found around the open holes and along the runways.
If you were to begin digging at one of the holes you would find a second runway, just below the soil surface, where these animals spend the rest of their time feeding on plant roots. Digging a little deeper, you would find another set of burrows 6 to 8 inches below the soil surface where they store (cache) food, build nests, and rear their young.
Unlike gophers, which breed only once during a season, voles begin producing their litters in late February and every 21 days thereafter. With litters ranging between four and six per female, a population can soon grow to astronomical proportions.
Changing the voles’ living conditions by either reducing or eliminating their food source and protection (habitat) will have the most pronounced and long-lasting effect. When food sources are eliminated voles will, because of their small territories, generally die. Some will migrate.
Weeds and grasses around plants, and hills of mulch around the crown, should be removed as they encourage feeding by voles. All dead and dying plant material should be raked from beneath the plants. Excessive ground cover provides an excellent form of protection for the voles, particularly during the winter when the mulch becomes a thermal blanket for the ground.
Traps and fumigants (gases) are ineffective for vole control. Traps will only catch a few of the animals that venture above the ground. Fumigants will escape from the many open holes of the burrow systems.
(poisons) used in baits can, if used properly, provide control within a short period of time. Baits should be scattered or placed around each burrow opening and in the voles’ runways between holes during the fall and early winter when the animals are the most active above the ground. Check with your local county Extension office for those registered.
This fact sheet is adapted from Oregon State University Extension Publication PNW215, Highbush Blueberry Production. The authors of Highbush Blueberry Production are – Oregon State University: Bernadine Strik, Glenn Fisher, John Hart, Russ Ingham, Diane Kaufman, Ross Penhallegon, Jay Pscheidt and Ray William; Washington State University: Charles Brun, M. Ahmedullah, Art Antonelli, Leonard Askham, Peter Bristow, Dyvon Havens, Bill Scheer, and Carl Shanks; University of Idaho: Dan Barney. PNW215, Highbush Blueberry Production can be purchased from the Department of Extension & Experiment Station Communications, Oregon State University. How to Order