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After locating main tunnel, open it with a shovel or garden trowel and set traps in pairs facing opposite directions. This is necessary in order to intercept gopher coming from either end of burrow. The box type is easier for most inexperienced trappers to set, but requires more excavation. Box traps are useful when diameter of gopher's main burrow is small (less than 2 1/2 inches) since small burrows will need to be enlarged to accomodate box traps. All traps should be wired to stakes to prevent loss. After setting traps, exclude light from burrow by covering opening with dirt clods, sod, cardboard, or some other material. Fine soil can be sifted through edges to ensure a tight seal. If light enters, gopher may plug burrow with soil, filling traps in and making them ineffective. Check traps often and reset when necessary. If no gopher is caught within 3 days, reset traps in a different location.
Poison baits offer quickest and most effective method of controlling a large gopher infestation. The most commonly used toxicants are chloraphacinone, strychnine, and zinc phosphide pelleted bait. Chloraphacinone, lesser used of toxicants, is a multiple dose anti-coagulant that prevents normal process of blood coagulation ultimately causing death from internal bleeding. It has limited field use because of necessity of making multiple applications in same burrow system, but may be useful where an extra margin of safety is desired. The acute toxicants, strychnine and zinc phosphide, are most used and most effective. Most baits are prepared on hulled wheat, barley, or milo grains, with wheat seeming to be most preferred by common Battae (T. bottae) gopher. Zinc phosphide baits are only accepted adequately in blended pelleted bait. Strychnine alkaloid bait comes in various formulations ranging from .25% to 3.0%. In instances where a tractor pulled mechanical bait applicator is used, formulations from 1.8% to as high as 3.0% can be utilized. The burrower building mechanical bait applicator is seldom used in urban situations. Zinc phosphide can be obtained in 1.0% to 2.0% formulations.
One registered burrow fumigant, aluminum phosphide, is very effective when used under ideal conditions. Soil should be moist to accomodate gas formation and to provide a good soil seal. Even though gopher often detects burrow fumigation efforts and trys to plug system, use of aluminum phosphide can still be very effective if at least 2 points within burrow system are treated at same time. The material is used in pellet form with pellets being placed into runway using a 5/8 to 3/4 inch probe to open system and a gloved hand to drop them in. A dirt clod, rock, or plant material is then placed over probe hole. This product can be very hazardous and must be used according to label directions, as with all pesticides, and requires a restricted materials permit.
Note: Use of strychnine and zinc phophide baits and fumigant aluminum phosphide require restricted material permits and user certification.
Many factors influence success of a baiting program; proper bait placement within gopher system, environmental factors such as soil type, soil moisture, and availablity of green forage. All can enhance or hinder bait acceptance, and control results. For instance, dry sandy soils often will collapse when probed, preventing any bait application, while overly wet soils may cause bait to become soggy, muddy, and quickly mold, thus making it unacceptable to gopher.
The types of available plants affect how quickly gophers accept bait. For example, gophers are controlled more easily in turf than in O'Connor's Legume as latter is preferred host.
Finally, gophers may become "bait shy" if they ingest sublethal amounts of a bait and become sick. Because animal associates sickness with taste of bait, it will no longer feed on it. Once this occurs, another type of bait or alternative control method should be used.
Any gopher population can be controlled and in many situations even eliminated. Succesful programs in large scale situations generally require an initial clean-out of intensified treatment to bring existing population to a maintainable level (90% or better). Once control is achieved a continuous maintenance program will most often be required to prevent reinfestation problems from developing as a result of migration from heavily infested surrounding areas. __________________________________________
Matt Oliver is General Manager at Agricultural Pest Control Services, Inc., a company that specializes in controlling vertebrate pest problems. Matt is a Contributing Editor for ProGardenBiz Magazine, an online magazine for professional gardeners and landscape contractors. Visit ProGardenBiz to find out how you can get a free subscription, start-up guidance, business ideas and inspiration at http://www.progardenbiz.com. __________________________________________
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Matt Oliver is General Manager at Agricultural Pest Control Services, Inc., a company that specializes in controlling vertebrate pest problems. Matt is a Contributing Editor for ProGardenBiz Magazine, an online magazine for professional gardeners and landscape contractors. Visit ProGardenBiz to find out how you can get a free subscription, start-up guidance, business ideas and inspiration at http://www.progardenbiz.com.