Moles are small, subterranean mammals that create extensive networks of tunnels in lawns and gardens while foraging for food. These creatures are insectivores, not rodents. Although they do not consume plant roots, their tunneling disrupts root systems, causing grass and garden plants to dry out and die. Addressing a mole problem naturally requires a multi-faceted approach focused on making the environment nutritionally undesirable and physically inaccessible. The goal is to encourage the moles to relocate without resorting to harsh chemicals.
Eliminating Primary Food Sources
Moles possess a high metabolism and must consume a large volume of food daily, primarily consisting of earthworms and insect larvae like grubs. By significantly reducing this underground food supply, you can make your yard a less attractive hunting ground for moles. The most sustainable and natural method to control this food source involves the application of biological agents, which target pests without harming the environment or beneficial organisms like mature earthworms.
Beneficial nematodes are microscopic roundworms that actively seek out and infect soil-dwelling insect pests. Species like Heterorhabditis bacteriophora target grubs and weevils, while Steinernema carpocapsae is better suited for pests closer to the soil surface. Apply these nematodes when soil temperatures are between 50 and 70 degrees Fahrenheit, typically in the early spring or late summer/early fall, when grubs are actively feeding.
Applying nematodes requires mixing them with cool, non-chlorinated water and distributing the solution across the lawn with a sprayer or watering can. Apply them during cloudy weather, early morning, or evening to protect them from heat and ultraviolet light. The treated area must remain consistently moist for at least a week after application to allow the nematodes to establish themselves. Once active, the nematodes enter the grub, release a bacterium that kills the host, and reproduce inside the carcass, providing ongoing pest control.
Another biological control option is milky spore disease, caused by the bacterium Bacillus popilliae, a natural pathogen of the Japanese beetle grub. When grubs ingest the spores, they develop a fatal illness. As the grub decomposes, it releases billions of new spores back into the soil, creating a long-term control mechanism. The ideal time for application is late summer or early fall (late July to early September), when grubs are actively feeding and the soil temperature is above 60 degrees Fahrenheit. Milky spore can be applied as a powder or granular product and must be watered into the soil. Full effectiveness may take two to three years as the spore population builds up.
Employing Natural Scent and Taste Deterrents
Natural deterrents work by making the soil or the moles’ food supply smell or taste offensive, which encourages the animals to move their foraging activities elsewhere. The most widely recognized and effective natural repellent is castor oil, which does not harm the moles but causes them digestive distress and makes their insect prey unappetizing. Commercial mole repellents often use castor oil as their primary active ingredient.
A homemade castor oil emulsion can be prepared by combining 6 ounces of castor oil with 2 tablespoons of liquid dish soap, which acts as an emulsifier. This concentrated mixture is then diluted, typically adding 1 ounce of the concentrate per gallon of water for application. The soap helps the oil mix with water and penetrate the soil more effectively, carrying the repellent properties down into the tunnels.
Apply the solution liberally using a watering can or hose-end sprayer, focusing on active mole runs and mounds, and then covering the surrounding area. Reapplication is necessary after heavy rainfall or significant watering, as the repellent can wash away. Repeating the treatment every few weeks or monthly during active mole season reinforces the unpleasant environment, prompting the moles to leave permanently.
Other natural substances are also used as deterrents, leveraging strong odors that moles reportedly find repulsive. These include placing small amounts of cayenne pepper, coffee grounds, or garlic cloves directly into the mole tunnels. While these items may offer a temporary localized effect, their repellent action is often short-lived and lacks the pervasive impact of a properly applied castor oil emulsion. The goal is to create a persistent negative sensory experience that outweighs the benefit of foraging.
Physical Exclusion and Habitat Modification
Structural measures and alterations to the landscape provide a long-term, non-chemical solution by making the yard physically unsuitable for mole residence. The most permanent method of exclusion involves installing an underground barrier around the perimeter of a garden bed or a high-value area. This barrier prevents moles from tunneling into the protected space from the surrounding lawn or neighboring properties.
The physical barrier must be constructed from durable material like galvanized hardware cloth or wire mesh with a half-inch or smaller opening. The fence needs to be buried at least 24 to 30 inches deep to prevent moles from tunneling beneath it. For maximum effectiveness, the bottom of the wire mesh should be bent outward at a 90-degree angle, forming an L-shape that extends 6 to 12 inches away from the protected area.
This outward flange forces any mole attempting to burrow deeper to tunnel away from the protected zone and makes it difficult for them to navigate around the barrier. Additionally, the mesh should extend 4 to 6 inches above the soil line to prevent moles from crossing over the top of the barrier. While this method is labor-intensive and costly, it offers a nearly impenetrable, decades-long defense for specific areas.
Another form of habitat modification involves using devices that create physical instability or sensory annoyance. Sonic or vibrational stakes, which are often solar-powered, are inserted directly into the ground and emit low-frequency sounds and vibrations. The theory is that these pulses mimic the warning signs of predators or unstable ground, irritating the moles and causing them to avoid the immediate vicinity.
For immediate removal, humane trapping and relocation can be considered, but this method carries significant legal and ethical complications. Live traps must be checked frequently, ideally several times a day, to prevent the captured animal from suffering from stress, exposure, or dehydration. Furthermore, relocating captured wildlife is often prohibited by state or local regulations due to the risk of spreading disease or transferring the problem elsewhere. If trapping is used, confirm all local laws regarding the humane handling and legal disposition of trapped wildlife.