Voles are small rodents, often mistaken for mice or moles, that commonly damage gardens and lawns by feeding on roots, tubers, and tree bark. These pests create visible surface runways and numerous small burrow entrances, posing a threat to valuable landscaping. Applying castor oil provides a humane, non-lethal method to deter voles by making their foraging environment unappealing. This article details the process of mixing and applying a castor oil solution to effectively encourage these animals to relocate.
Why Castor Oil Acts as a Vole Deterrent
Castor oil functions primarily as an irritant and deterrent, not a poison. The active component, ricinoleic acid, creates a highly offensive odor and taste when it permeates the soil, which voles find repulsive. Since voles rely heavily on their sense of smell to locate food sources, the strong presence of the oil drives them away from the treated area. The oil coats the roots and soil, making their primary diet unpalatable and their tunneling environment uncomfortable. This method encourages the voles to seek an alternative habitat outside the protected zone rather than causing them direct harm.
Mixing the Solution
To create the concentrated base, combine one part castor oil with one part liquid dish soap in a container. For example, mixing one cup of each is a common starting point. The dish soap serves as an emulsifier, which is necessary because oil and water do not naturally mix. Without the soap, the castor oil would separate, preventing it from dispersing evenly when applied to the soil.
Vigorously stir or shake this mixture until it becomes thick and takes on a creamy, uniform consistency. This concentrated emulsion is then ready to be diluted for application. A typical dilution ratio involves mixing four to six tablespoons of this concentrate with one gallon of water. The final solution must be shaken well before and occasionally during use to maintain the emulsion and ensure even coverage.
Applying the Deterrent to Vole Tunnels and Runs
The liquid solution is best applied using a garden sprayer for uniform distribution over large areas. The key to success is thorough saturation; aim to drench the soil rather than simply misting the surface vegetation. Ensure the solution penetrates deep enough to coat the roots and active tunnel systems, typically the top two to three inches of the ground.
Begin the application by treating undamaged areas first, working toward the most heavily infested zones. This encourages the voles to exit in a specific direction. Pay particular attention to surface runways—the irregular, clipped paths of grass—and burrow entrances, soaking them liberally. If using a hose-end sprayer, set the dial to a high concentration setting.
After applying the solution, water the treated area for about ten minutes, or until the repellent has soaked into the soil. This helps the castor oil penetrate deeper into the tunnels, increasing contact with the soil where voles travel and feed. For smaller, concentrated infestations, the solution can be poured directly into the burrow entrances.
Monitoring and Reapplication Schedule
After the initial application, voles should begin moving out of the treated area within a few days to a week. To check for continued activity, lightly disturb a section of the runways or cover a burrow entrance with soil. If the disturbed areas are repaired or the entrance is reopened within 12 to 24 hours, the voles are still active in that location.
The castor oil’s effectiveness diminishes over time, particularly after significant rainfall, which can dilute its concentration. A maintenance schedule requires reapplication every four to six weeks, or immediately following heavy rain events. Reapplying the solution regularly helps maintain a consistent, unappealing environment, preventing the animals from returning. Treating the area in the late fall before the ground freezes is especially effective, as voles are often most active in their search for food during the winter months.