The appearance of numerous earwigs (Order: Dermaptera) in a yard is a direct result of an environment perfectly suited to their survival. These insects, often recognized by the distinctive forceps-like pincers, or cerci, extending from their abdomen, are a common household and garden concern. While the cerci may look unsettling, they are generally harmless to humans, used primarily for defense and courtship. A high population of earwigs indicates the presence of abundant moisture, shelter, and food sources, all of which must be addressed to restore balance to the yard.
Environmental Factors That Draw Earwigs
Earwigs have an absolute reliance on moisture to prevent desiccation, which is the single most important factor driving their population density. They are nocturnal, spending the daylight hours hiding in dark, damp places to conserve body water. Unusually wet seasons or a consistently overwatered landscape can create the necessary microclimates that allow their numbers to swell.
This moisture-dependent behavior means a concentration of earwigs can often be traced back to areas with poor drainage, leaky outdoor spigots, or clogged gutters that deposit water near the foundation. Thick organic mulch, dense ground cover, and heavy leaf litter retain moisture and provide the cool, humid conditions these insects require. Any item that creates a tight, dark space—such as woodpiles, stepping stones, or cracks in the foundation—becomes a preferred daytime refuge.
The sheer number of earwigs is a reflection of how well the environment is meeting their needs for both hydration and shelter. Female earwigs lay clusters of eggs in the soil and guard them over winter, further concentrating the population in protected, moist locations. When these ideal conditions are met throughout a yard, the result is a thriving population that becomes noticeable when they emerge at night.
Primary Food Sources and Plant Damage
Earwigs are omnivorous scavengers, meaning they sustain themselves on a varied diet of both plant and animal matter. They primarily consume decaying organic material, molds, and fungi found within the soil, mulch, and leaf litter. This scavenging role can be beneficial, as they also prey on small, soft-bodied insects like aphids, mites, and insect eggs, acting as natural predators in the ecosystem.
However, when their population grows large, earwigs shift their focus to living plant tissue, turning into garden pests. They are particularly drawn to tender plants, including seedlings, lettuce, and the petals of ornamental flowers such as dahlias and marigolds. Feeding typically occurs at night, leaving characteristic irregular holes in leaves and blossoms, giving the plant a ragged, chewed appearance.
They may also damage fruits that are in contact with the ground, such as strawberries, or chew on the silks of corn. The presence of a large population suggests an overabundance of both decaying matter and vulnerable young plants to feed on.
Removing Yard Attractants
The most effective long-term strategy for reducing earwig numbers involves modifying the landscape to eliminate the environmental conditions they require. Reducing surface moisture is a priority, which means correcting drainage issues and ensuring downspouts divert water well away from the house foundation. Watering plants in the morning allows the soil surface to dry out before the earwigs become active at night, making the area less hospitable.
Attention must be paid to removing their extensive network of daytime hiding places around the perimeter of the home and garden. This involves creating a debris-free zone, ideally 6 to 12 inches wide, by pulling back organic mulch from the foundation.
To limit shaded, humid microclimates:
- Piles of leaf litter, grass clippings, and old boards should be removed or relocated far from vulnerable plants.
- Firewood and lumber should be stacked on a raised platform and stored away from the exterior walls of any structure.
- Trimming dense ground cover and ivy near flower beds and foundations is necessary.
- Switching from organic mulch to inorganic alternatives, like gravel or stone, around the foundation helps maintain a drier perimeter.
Direct Control Methods
While landscape modification provides prevention, direct control methods can quickly reduce an existing high population. Simple trapping techniques exploit the earwig’s natural instinct to seek out dark, tight, moist spaces for daytime rest. Rolled-up damp newspaper, short sections of garden hose, or bamboo tubes placed near infested areas serve as effective traps.
These traps should be set out in the evening and collected in the morning, with the trapped earwigs disposed of in a pail of soapy water. Another popular method involves using a low-sided can, such as a tuna fish can, sunk into the ground so its rim is at soil level. The can is filled with a half-inch of vegetable oil mixed with a small amount of fish oil or soy sauce as an attractant, causing the earwigs to drown.
For a physical barrier, a light dusting of diatomaceous earth can be applied to dry areas around vulnerable plants or foundation entry points. This finely ground powder works by physically damaging the earwig’s waxy outer layer, leading to dehydration and death. Targeted applications of residual insecticides, such as those containing spinosad, can be used as a last resort in areas of heavy congregation.