Piute Ground Squirrel populations on agricultural lands are increasing in southwest Utah. It is a small gray squirrel found mostly in the Great Basin. It eats alfalfa, grasses and other agronomic crops. The reduction in alfalfa and other crop yields and the cost of controlling Piute ground squirrels to farmers in western Utah exceeds hundreds of thousands of dollars annually.
(Ground squirrel damage (Mary Burrows, Montana State University, Bugwood.org)
Piute ground squirrels live in colonies and construct underground burrows that have a number of entrances. The burrows may be up to 6 feet deep. They hibernate from September through January. Males usually become active above ground 2-3 weeks before the females in the spring, sometimes as early as the first of February. The females become active and emerge several weeks later, when breeding takes place. A few squirrels may be active above ground throughout the year. The young are born after a 23-day gestation period with 7 to 10 young per litter. Generally only 1 litter is produced each year.
Squirrels are increasing in infested areas each year and are showing up in places not previously found. Previous control programs such as shooting, flooding, treating with zinc phosphide and gopher bait have not been effective. For the past 10 years Utah State University Extension has conducted a number of trials to determine which baits are most accepted and when is the best time to apply them. They have found:
- Piute ground squirrels prefer small pelleted bait and not whole grain bait.
- Rozol vole bait is now approved in Utah under Section 24(c) special need label for station and spot baiting only and has shown up to 75% control when applied before alfalfa greens up in the spring.
- Carbon Monoxide machines (P.E.R.C.) are effective in fumigating the burrows, but are expensive and time-consuming (4-5 minutes to treat each hole).
- Ignitable gas cartridges are effective but are quite expensive and can cause a fire hazard in dry environments.
- Aluminum Phosphide comes in tablet forms and reacts with the moisture in the soil to produce a lethal phosphine gas that is toxic to all mammals (including humans). Extension research has shown 97% control of ground squirrels by using the Aluminum Phosphide tablets. The use of this product is strictly prohibited within 100 feet of any building and extreme caution is required