Rodent Repellent

Voles, mice and rabbit damage can be detrimental to trees and shrubs. Subsurface damage is often caused by voles, which feed on the roots and bark of trees and shrubs. Mice feed on saplings and shrubs below the snow and within the grass layer. Rabbits assault bark and tender buds on areas higher up than the reach of voles and mice.

There are several management options available to you as a gardener:

Use protection - Protect trunks by placing a cylinder of ¼” (or smaller) mesh, hardware cloth. Or put plastic drainpipe around the trunk. The guards should extend two inches below the soil line (as long as they don’t damage roots). Place 18- 24 inches above the anticipated snow line. Guards should be removed or reinstalled each spring to prevent girdling.

Repellants -The most effective repellants for rodents contain thiram, a fungicide that is distasteful, yet unharmful, to rodents. Thiram is a water-soluble spray or paint. Apply it with a surfactant. One application is usually enough for the entire dormant season. Apply multiple applications during the growing season.

Habitat modification - Discourage rodents by reducing grasses and other vegetation that pests use for cover from predators. Mow or chemically control grasses within a 4′ diameter circle around trees. Also, discourage rabbits by reducing vegetative cover, brush piles and other hiding places.

Other - Hunting and trapping, although labor intensive, can be effective. However, mice and vole populations usually don’t respond well to trapping or other extermination, such as rodenticides. High reproductive rates draw in pests from surrounding areas. They take advantage of abundant food and habitat following local extermination. Fumigants and electromagnetic or ultrasonic devices are not effective for long-term control of rodents.

Growers are advised to protect their perennials from damage caused by rodents now that winter is near. Small animals will invade overwintering structures, eat most perennials and burrow into pots if given the chance. The most likely critter to cause havoc is the meadow vole. The head and body of meadow voles measure 3 to 5″ long and the tail is 1½ to 2½” long. They have brown body hairs mixed with black guard hairs; belly hairs tipped gray and small eyes and ears. Meadow voles are active day and night, year-round. They do not hibernate. They feed all winter long on tubers, bulbs, rhizomes, stems, roots, and seeds and occasionally on insects and animal remains. Meadow voles construct many tunnels and surface runways with numerous burrow entrances. These surface runways are the most easily identifiable sign of voles. By the time the runways are noticed, damage is usually done. Voles are prolific breeders. They may breed throughout the year, but most commonly in spring and summer.

To identify animals responsible for damaged plants in your overwintering greenhouses, try using signs. One way is to place some non-toxic bait such as apples out in a problem area and see what kind of damage is done to that bait. The culprit can be identified by the excrement that is left behind. Another way to identify the animal is to capture one, using a small live trap or a mouse snap trap. Good baits include peanut butter-oatmeal mixture or apple slices. Once the animal is identified, control measures can be taken. It should be noted that voles are capable of carrying diseases that affect humans, so be careful and use protective clothing when handling voles.

The first step to prevent damage caused by rodents is to deny them access to your overwintering greenhouses. Make them rodent tight. Use fine mesh screen wire such as hardware cloth around the perimeter of the greenhouse. Bury it under ground and bend it outward at a 90 angle leaving it at least 6″ deep.

Next, mow and clean up the natural vegetation close around the greenhouses to eliminate protected areas for rodents. Most of our wildlife animals will not venture across a wide-open space because they are much more vulnerable to natural predators.

Trapping is not effective for controlling large vole populations, but can be used to control small populations. Place mouse snap traps containing bait perpendicular to the runways.

The most effective repellent many say is The Yeoman Plug-in Rodent Repellerwhich emits 2 kinds of electronic waves: electro magnetic waves and ultrasonic waves which rodents find unpleasant. Inaudiable by humans and domestic pets (dogs, cats and fish), these electronic waves encourage the rodents to move out of the vicinity.

Chemical repellants are available that can be used on plants. Some repel by giving off an offensive odor and others are taste repellants. These products reportedly work for a number of animal pests. Some of these products may not be persistent and some are easily washed off and need to be reapplied.

Finally, when all else fails, there are toxic baits that are effective for reducing the population. One of the most effective and common baits is zinc phosphide treated, cracked corn, or oats. It is a single-dose toxicant available in pelleted and grain bait formulations and as a concentrate. Anti-coagulant baits are also effective in controlling voles. Anticoagulants are slow acting toxicants requiring from 5-15 days to take effect. Multiple feedings are needed for most anti-coagulants to be effective. Toxic baits can be harmful to children, pets and wildlife and should be used with utmost caution. Read and carefully follow the directions and safety precautions on the label of any of these products.