Integrated Pest Management - Richardson Ground Squirrels
Richardson ground squirrel, commonly known as the gopher is found throughout Mountain View County. The Richardson ground squirrel is a burrowing rodent that spends most of it's life underground, hibernating for up to eight months of the year.
Natural mortality among Richardson's ground squirrels is quite high, particularly in males. As a result, the sex ratio among adults is about four females for each male. Females live about four years (maximum six), on average, while males usually live only one year (maximum two to three).
When it comes to controlling Richardson's ground squirrel there are several options available to Mountain View County Producers. Not all solutions offered will be suited to the scope of the infestation, and may not be economically feasible in some situations.
Cultural control
This has shown limited success. Some research has been conducted on the effect of tall vegetation on ground squirrel populations and movements. The data, while limited, indicates that squirrels may move out of tall vegetation stands to more open grass fields. This would indicate that overgrazing could intensify an existing problem. Once ground squirrels have been removed from a crop area, re-invasion can be substantially slowed by destroying their old burrow systems through deep tillage.
Chemical Control
The chemical options are the most widely used and likely will be the most cost effective for large infestations. The two most common acute poisons registered for ground squirrels are strychnine alkaloids and anti coagulants. Strychnine causes death by entering the blood stream and interfering with the central nervous system, resulting in convulsions and eventually respiratory failure. Anticoagulants interfere with the clotting mechanism of the blood and cause death from internal bleeding three to four days after the bait is consumed. Anticoagulants may require more than one treatment to be effective.
In Canada Ready To Use (RTU) Strychnine baits are legally bound by a maximum concentration of 0.4 %. Rumors often circulate about higher concentration baits, but they do not exist. There is also much debate over (fresh mixed) "wet" and dry baits. Chemically the concentrations are identical. Wet baits are intended to be prepared and used within one week. Dry baits have a wider application window because they will not mold if stored for extended periods. If the ground squirrels will consume either bait, the effectiveness will be identical.
Chemical baits are most effective when applied early in the season. Once an alternate food source has been established ground squirrel consumption of bait will be limited. Repeated baiting with the same bait during the same year is generally unsuccessful. Baiting should be done thoroughly and correctly the first time. Always carefully read and follow all label directions for products used.
Non-chemical
These options include Exit® and shooting. Exit® was registered in the last couple years as a fumigant. It is essentially a mustard concentrate soap-based foaming agent that asphyxiates rodents when applied in the burrow. It contains no toxic chemicals and therefore is safe for residential/urban areas where control measures are limited. Further detail can be found on their website at www.exitholdings.com Shooting has proven to be perhaps the most effective method of control. When done safely and legally it is the most assured system for success.
Anhydrous Ammonia received a temporary 1 year registration in 2005 and it remains to be seen if it will be a legal control method in 2006. Gas exploding devices using propane or acetylene have not proven to be safe, reliable or effective. Studies have shown these devices reduced ground squirrel populations by only 40 per cent and did so at a very high cost.
In 2006 Mountain View County will be distributing Fresh Mixed Strychnine Bait for Maxim Chemical - the same bait offered in 2005. Program details and costs have not changed in 2006. For further information contact the Agriculture Department at the county office 335-3311.
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