Monday, Dec 18, 2017
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County of Madera


Vertebrate Pest Management

The control of ground squirrels in California is important both to prevent destruction of agricultural crops and facilities, and to decrease the potential for rodent-borne disease. With litters averaging six to eight young, ground squirrels have enormous reproductive capabilities. There are several essential steps to consider before control is undertaken:

  1. Pre-bait with oats to determine if squirrels are taking grain, allowing use of toxic grain bait.
  2. If grain cannot be used, determine if soil is moist, allowing use of burrow fumigants.
  3. If fumigants cannot be used, consider -trapping or shooting.

The chart below depicts an annual control program. The hibernation and estivation periods, as well as the control measures, vary with climatic conditions by as much as four weeks. Squirrels are generally inactive in December and January, and the weather is too cool for effective fumigation. Spring brings out the squirrels, but they are feeding on vegetation in preference to grain. Moist soils and warmer weather offer good conditions for burrow fumigation. In late spring until summer temperatures rise, squirrels feed on seed, providing an opportune time to offer-toxic baits. Squirrels are again inactive at the height of summer heat, and the soil is too dry for effective fumigation. As the weather cools in autumn, toxic baits are again effective. Fall rains bring good soil conditions for fumigation, prior to the cold of winter.


An effective and economical program depends greatly on monitoring. Ready knowledge of changes in rodent activity, bait acceptance, and degree of kill allow timely decisions and action.



Construct bait station from PVC pipe having a diameter no larger than 4" and no smaller than 3". Use white or gray pipe; black pipe will absorb heat, discouraging squirrels from entering.

Place bait stations at or near colony sites. Do not place stations at site where feeding damage is occurring. If feeding has not begun within a few days, change location of station.

When station is initially placed, use 3 to 5 pounds of oat groats as a pre-bait. While pre-baiting does not affect control attained with anticoagulants, it has been shown to bring down the overall cost of the treatment program.

When the pre-bait has been taken, replace with :0.005% diphacinone bait. Anticoagulants require multiple feedings over several days to achieve control. Keep bait in station at all times during treatment period; intervals longer than 48 hours between feedings allow recovery of the coagulation mechanism. Do not allow the bait to get wet, either in the bait station or in storage.

Wash hands thoroughly with soap and water after handling bait.

If used in public areas, remove stations when bait is no longer taken.


Anticoagulants are poisonous to all warm-blooded animals, including humans. Store poisoned grain in locked containers OUT OF REACH OF CHILDREN and livestock. Do NOT place in unlabeled containers.

Do NOT store in areas accessible to pets. Dogs are especially sensitive to diphacinone, and have been known to eat bait from the bag with lethal result.

Do NOT handle sick or dying rodents. Fleas abandoning dead rodents pose a health hazard to humans and pets.

Constructing a bait station



Use a nail or sharp instrument to punch five holes in the end cap of the cartridge where indicated. Insert the fuse one-third to one-half its length in the central hole.

Gopher ControlLight the fuse, and immediately place the cartridge, fuse-end first, into the burrow. Push the cartridge as far along the tunnel as possible, using a stick or shovel handle to avoid fleas inhabiting the burrow. Close the burrow opening with a shovelful of soil as soon as ignition is noted.

Watch nearby burrows for escaping smoke, closing with soil as needed.


Lighted cartridges may at times produce open flames. Do not use near structures, or where burrow system may pass beneath a structure. AVOID USING NEAR FLAMMABLE MATERIALS OR WHERE BRUSH FIRE MAY RESULT.

Unused cartridges must be locked up, and stored away from open flame or flammable material.



Pocket gophers lead an almost completely subterranean existence, venturing above ground only to push dirt out of the burrow, graze on vegetation near the burrow entrance, or seek new territory after weaning. Each gopher establishes its own territory ranging from 200 to 2,200 square feet. The burrow system consists of main tunnels 2 to 2.5 inches in diameter, generally running parallel with the soil surface. Dirt from excavation is pushed out lateral exits, forming horseshoe-shaped mounds, which are plugged with fresh dirt. Feeding laterals are nearly vertical, having the appearance of "punctures" in the soil, and are closed with inconspicuous plugs. Gopher burrows are sometimes utilized by other animals, including toads, snakes, mice, and arthropods.

Gophers do not hibernate or become completely inactive at any time of the year. Litters average five to six young, with frequency of pregnancy increasing with size and age of female. Gophers rarely live beyond three years. Natural predators include hawks, owls, gopher snakes, foxes, and coyotes.

Gopher control measures include toxic grain baits, fumigants, exclusion, flooding, and trapping. All bait material is to be placed below ground, and probes are available for the location of tunnels, as well as the dispensing of bait. Our office does not currently offer for sale any products effective for gopher control. Baits effective against gophers can be bought at most home and garden stores.

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Contact the Ag Dept.

Agriculture Department
332 South Madera Avenue
Madera, CA 93637
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General County Contact
200 W. 4th Street
Madera, CA 93637
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Use this number to get general information about the County or County departments.  

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