If your garden looks like a winding road map and the bases of your trees and shrubs are totally bare, you may have a vole problem. Signs of vole damage according to the Home Orchard Society include surface runways with 1-inch holes leading to underground tunnels; girdled trees and shrubs, which have been gnawed bare all the way around the base, and green or grey rodent droppings.
Because voles eat grass, roots, seeds, and bulbs, and reproduce at a rapid rate, they can quickly cause a lot of damage. Often, they do most of their damage in the winter, which means this damage and the vole population can increase unnoticed for months beneath snow cover. Before you can begin repairing vole damage, you need to get rid of the voles. To kill voles fast, you have two basic options: traps and rodenticides (rodent poison).
Decide whether you will use traps, rodenticide, or a combination of both. Traps, which are easy to use, are also the safest option in terms of the risks they pose to the environment, humans and non-target animals. In addition, they cause instantaneous death. However, traps may not be feasible for everyone. If the vole affected area is larger than an acre, the use of traps would be costly and time-consuming.
Determine the number of traps you will need (if you have decided to use traps) by making a tally while you walk the affected area. You will need one mouse snap trap per runway and/or hole or enough to place traps about 15 feet apart.
Place a single mouse trap perpendicular (at a right angle) to each runway. Make sure the triggers are in the runways. Because the voles travel the runways, baits are not necessary. If you want to use bait, the University of Nebraska Extension recommends that you place a peanut butter/oatmeal mixture or a small slice of apple on the triggers.
Place a box with a 1- to 2-inch hole cut on both ends over each trap if they are baited. Any kind of box will do as long as there is still enough room for the trap to snap. Most shoe boxes are about the right size. The box will help keep other animals, such as birds and squirrels, from triggering the traps. To some extent, it may also help keep other animals from eating the dead vole, so you may want to cover the traps even if they are not baited. Several companies sell traps that have built in covers.
Scout the area daily and dispose of any vole carcases by securing them inside a sealed plastic bag. Throw them out with the rest of your garbage. Be sure to wear rubber gloves when you handle dead voles. Dispose of the vole carcases whether you are using traps or rodenticides.
Continue to place traps in the same locations until you no longer trap any voles. Move the trap to a new location, and continue. Continue to use the traps for at least two to three weeks to gain control of the vole populations. You may still need to set traps again occasionally afterward because vole control requires an ongoing effort.
Rodenticides are an effective alternative when traps are not feasible, but they must be handled with care. To minimise the potential dangers associated with their use, rodenticides must be applied according to the package directions or by a certified handler. A professional will be certified to use rodenticides containing chemicals, such as zinc-phosphide, that at have been labelled "restricted-use" by the EPA.)
You can also purchase an over-the-counter rodenticide at your local hardware store or online and follow the package instructions. There are number of rodenticides on the market, and some are specially made to kill voles.
Consider rodenticides that contains cholecalciferol (vitamin D3). Although this is a bit harder to find, it is the fastest, safest bait choice for the common person to use. It is commonly used in small doses in supplements for human consumption and is only toxic in large doses. Therefore, it poses less risks for humans and non-target animals.
If you choose to use a rodenticide, be aware that some have the potential to cause "bait shyness," a condition in which the voles actually learn to avoid what is killing them. Another problem you may encounter with anticoagulant rodenticides is that the voles sometimes develop a resistance to the chemicals. If you suspect either problem, consult a professional and or vary the type of bait you use. After you reestablish control over your lawn or garden, begin an integrated pest management program as recommended by the EPA. Such a program would involve multiple methods of prevention and control.
Any rodenticide can be potentially hazardous if it is misused, so be sure to follow product directions precisely, and/or contact the manufacturer with any questions or concerns. Some rodenticides contain chemicals such as strychnine, bromethalin and zinc phosphide, which can kill voles faster than an over-the-counter rodenticide, but many of these are categorised as "restricted-use" by the Environmental Protection Agency (EPA) and can only be bought and used by certified applicators. Restricted-use products pose a higher risk of toxicity to humans and non-targeted animals. Most over-the-counter rodenticides contain anticoagulants. Because a vole has to feed on an anticoagulant bait for several days to build up a lethal amount in its body, the carcase of a dead vole contains a highly concentrated dose of the poison that could kill an unsuspecting cat, dog or bird.