The sudden appearance of mole hills and raised ridges can quickly transform a manicured lawn into a chaotic landscape. Homeowners often mistake this tunneling activity as a search for plant roots, but moles are insectivores with a high-protein diet living exclusively beneath the surface. Control strategies frequently focus on removing this food source, particularly the subterranean insect larvae that moles consume. The popular belief is that a hungry mole will simply leave the yard, but the effectiveness of this approach depends on fully understanding their specific dietary habits.
Identifying the Mole’s Diet
Moles are driven by an immense metabolic need, requiring them to consume a large quantity of food daily. Their diet consists almost entirely of invertebrates found within the soil, which they hunt by constantly patrolling their intricate tunnel systems. The primary component of this diet, making up a majority of their food intake, is the common earthworm.
While earthworms are the staple, moles also feed opportunistically on insect larvae. This includes white grubs from Japanese beetles and European chafers, along with other items like ants, spiders, and snail larvae. These make up the remainder of the mole’s high-calorie insectivorous diet.
Strategies for Eliminating Primary Food Sources
Since earthworms are difficult to eradicate without compromising soil health, the focus of food source removal is typically on reducing the population of subterranean insect larvae, or grubs. This grub control can be achieved through both chemical and biological methods, each with specific timing requirements.
Chemical Controls
One approach involves the use of systemic chemical insecticides, which target the grubs as they feed on grass roots. Preventive products containing active ingredients like imidacloprid or chlorantraniliprole are highly effective when applied correctly. Chlorantraniliprole can be applied early in the spring, as it is less water-soluble and moves more slowly through the soil to the root zone.
Other common preventative compounds, such as imidacloprid, thiamethoxam, or clothianidin, are best applied later, generally between mid-June and early August. These chemicals must be watered into the soil immediately after application to ensure they reach the feeding zone of the newly hatched grubs. If a grub problem is discovered later in the season, a curative insecticide like trichlorfon or carbaryl may be applied, though these are typically less efficient.
Biological Controls
Biological controls offer a non-chemical alternative to reduce grub populations. Beneficial nematodes, specifically the Heterorhabditis bacteriophora species, are microscopic worms that parasitize grubs. These nematodes carry a bacterium that is lethal to the grub within 48 hours of infection. They are applied by mixing with water and spraying onto the lawn, ideally on a cloudy day or in the evening, as they are sensitive to ultraviolet light.
Another biological method, Milky Spore, uses the bacterium Paenibacillus popilliae to target Japanese beetle grubs. The grub must ingest the spore while feeding, and the effect is highly specific to the Japanese beetle species. Establishing effective control often requires multiple applications over two years, but once the bacteria is established in the soil, its effects can last for a decade or more.
Limitations of Food Source Removal
Despite successfully eliminating insect larvae, homeowners often find that the mole problem persists or temporarily worsens. This lack of complete resolution is due to two primary limitations that undermine the food source removal strategy.
The first major hurdle is the earthworm factor, as earthworms comprise the vast majority of the mole’s diet. Earthworms are considered beneficial for soil aeration and health, making it impractical to eliminate them. Because moles are primarily sustained by earthworms, removing grubs only targets a secondary part of their food supply, leaving the main source intact.
The second limitation is the mole’s high mobility and migratory behavior. Moles are capable of digging up to 60 feet of new tunnel per hour and will continually forage across a wide range. When a local food supply is reduced, the mole will expand its foraging territory, often migrating to an adjacent yard. They may also increase their digging activity as they search desperately for food, resulting in a temporary increase in visible damage.
Effective Alternatives: Direct Population Control
Because food source reduction is often ineffective on its own, direct population control remains the most reliable strategy for eliminating moles. This approach focuses on removing the animal itself from the tunnel system.
Trapping
Trapping is widely considered the most consistently successful method for mole removal. Effective traps, such as the scissor, harpoon, or choker loop styles, are designed to be set directly into the mole’s active runways. Identifying a main, active runway, rather than a temporary feeding tunnel, is paramount for successful placement.
Toxic Baits
Toxic baits offer an alternative to traps and have become more effective with advances in their formulation. Modern baits are typically shaped like a synthetic worm to mimic the mole’s natural prey, which is far more attractive than older grain-based products. These products often contain the active ingredient bromethalin, which is a neurotoxin.
The worm-shaped bait must be placed directly into an active tunnel, usually by poking a hole and dropping the bait inside, being careful not to collapse the runway. The mole consumes the bait, and death usually occurs underground within 12 to 36 hours. Placement in the deep, daily-use tunnels is essential for the success of both trapping and baiting methods.