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.
DIRECTIONS FOR USE OF ANTICOAGULANT
BAIT
FOR GROUND SQUIRREL CONTROL
Instructions:
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.
PRECAUTIONS:
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.
DIRECTIONS FOR USE OF GAS CARTRIDGES
FOR GROUND SQUIRREL CONTROL
INSTRUCTIONS:
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.
Light
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.
PRECAUTIONS:
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.
KEEP OUT OF REACH OF CHILDREN.
GOPHER CONTROL
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.
