Moles are small, subterranean insectivores that spend almost their entire lives underground in search of food. They are not rodents, but rather mammals related to shrews, characterized by their powerful, paddle-like front feet. While rarely seen above ground, their continuous activity beneath the surface causes significant aesthetic and functional damage to turfgrass.
The Specifics of Lawn Damage
The most immediate and visible sign of mole activity is the presence of molehills, which are small, conical, or volcano-shaped mounds of soil scattered across the yard. These mounds result from the mole pushing excess dirt to the surface as it excavates deeper tunnels. Another common sign is the appearance of raised ridges or runways that snake across the lawn, which are tunnels just beneath the surface.
These shallow tunnels, or feeding runs, cause the most harm to the grass’s health. As the mole pushes through the soil, it lifts the turf and severs the fine roots of the grass blades. This disruption causes the affected sections of grass to detach from the soil, preventing the roots from absorbing necessary water and nutrients. The grass above the runs will quickly turn brown and die, creating unsightly, linear patches of dead turf.
Understanding Mole Behavior and Diet
Moles are insectivores, and the damage is a side effect of their relentless search for food. Their diet consists primarily of earthworms, their favored prey, along with other subterranean invertebrates like insect larvae and grubs. They are not interested in consuming the roots of the grass or other plants.
Their high metabolism requires them to consume a large amount of food daily, often eating between 70% and 100% of their own body weight every 24 hours. This drives the mole to construct vast, interconnected networks of tunnels for foraging, meaning the damage to the lawn is continuous.
The location of these tunnels is directly related to the availability of their prey. Moles will dig shallow runs just beneath the surface when the soil is moist and cool, as earthworms and insects move closer to the top layer. When conditions are dry or frozen, the moles will tunnel deeper to follow their food source, resulting in the appearance of the deeper, volcano-shaped mounds.
Differentiating Mole Damage from Other Subsurface Pests
Mole damage is distinguished by its characteristic volcano-shaped dirt mounds, which typically do not have a visible entry hole in the center. The presence of raised, spongy surface ridges is also unique to the mole.
Gophers, in contrast, leave behind crescent or fan-shaped mounds of soil, and a plugged hole is usually visible off to one side of the mound. Voles, which are small rodents that eat plant material, do not create dirt mounds at all. Instead, voles leave small, clean, round, open entry holes and create above-ground, clipped-grass runways that look like narrow paths through the turf.
Effective Management and Control Strategies
Trapping is considered the most reliable and effective method for removing moles once an active infestation is confirmed. The first step involves locating an active runway by pressing down on a section of the raised tunnel and marking the spot. If the mole repairs the collapsed section within a day or two, the tunnel is active and is a prime location for setting a trap.
Traps designed for moles, such as scissor-jaw or harpoon traps, are set directly over or into the active tunnel. These mechanical traps are triggered by the mole as it moves through the runway, eliminating the individual causing the damage. The placement of the trap must be precise, following the manufacturer’s directions.
Reducing the mole’s food source, particularly grubs, can make the lawn less attractive, but this is not a comprehensive solution. Grub control products eliminate beetle larvae but do nothing to deter the mole’s primary food, the earthworm. Some homeowners experiment with castor oil-based repellents, which are intended to make the soil smell and taste unpleasant to the mole. While these products may cause temporary movement, their effectiveness varies widely.