Zinc phosphide bait, like its fumigant cousin, kills prairie dogs with the use of phosphine. Once the zinc phosphide bait is consumed, it reacts with moisture in the gastric juices to liberate phosphine gas. The prairie dog inhales the gas and dies by suffocation.
Application consists of two visits: an application of pre-bait and the application of the bait. During the pre-bait, plain oats are applied to entice and train the prairie dogs to pick up the bait. The bait is applied after the prairie dogs show that they have accepted the pre-bait. The pre-bait and bait are to be applied at the rate of 1 teaspoon per active mound and isto be scattered on or near the mound.
For Black-tailed prairie dogs, zinc phosphide application can take place from July through February. For White-tailed prairie dogs, due to their hibernation, some zinc phosphide labels allow it to be applied in the spring.
Zinc phosphide poses a very slight risk of secondary poisoning, although the carcass of a prairie dog is not generally toxic enough to cause any harm to a larger animal that may feed upon it. It does, however, pose a threat to non-target species that have access to the bait itself. All livestock and pets should be kept from the area for at least a couple of weeks and great care should be taken to avoid any location where waterfowl may access the bait. Frost, dew, rain, and sunlight will eventually degrade any unconsumed bait.
There are two types of voles in our region, meadow voles and prairie voles.
Best known for the damage they cause to the base and roots of small trees and shrubs and the trails they leave in lawns, voles do their greatest damage underneath the cover of snow, when they can forage all day and night, safe from the constant threat of predators.
Where possible, we prefer to use zinc phosphide baits for the treatment of voles as the bait is both very effective and tends to be a bit safer for pets and other wildlife. However, the use of zinc phosphide is banned for residential use. It can be used on non-residential lawns as well a number of other locations including some crop land, rangeland, groves, vineyards and golf courses.
For residential use, vole control is limited to anti-coagulant baits, traps, habitat modification, exclusion and repellants. Unfortunately, all but the baits are impractical for larger areas of infestation.
Having outdoor cats in the area can help in the control effort. However, voles are known for their prolific breeding. With a very high mortality rate, they need to out-breed their predators. Voles will have 1 to 5 litters per year on average, but can have 10 or more litters, and in a year. Their young reach maturity in a little over a month and will have their own litters.
Voles can be treated with either zinc phosphide or anti-coagulant baits any time of the year if the infestation requires it. However, the best time to treat voles is in the fall, before we might get any lasting snow cover.
Control efforts and cost will vary according to the property and the extent of the problem.For cropland, orchards, golf courses and larger lots where we can use zinc phosphide, we charge by the acre.
