Earwigs, belonging to the order Dermaptera, are easily recognized by their elongated bodies and distinctive pair of forceps-like pincers (cerci) at the rear end. The most common species in North America is the European earwig (Forficula auricularia), an omnivorous and primarily nocturnal insect. Generally, earwigs are considered minor nuisance pests in arboriculture and rarely, if ever, cause the death of a mature, healthy tree.
Earwig Diet and Ecological Role
Earwigs are opportunistic feeders with a highly varied diet, which explains why they are frequently found on trees. As scavengers, they consume decaying organic matter, fallen leaves, fungi, and soft, moist plant material. This behavior helps break down debris and return nutrients to the soil, contributing to the overall health of the ecosystem.
Their presence on trees often serves a purpose other than feeding on the plant. Earwigs are voracious predators of smaller, soft-bodied insect pests, including aphids, mites, and insect eggs. They contribute significantly to suppressing pests like woolly apple aphid and pear psylla, particularly in fruit orchards. The benefits of their predatory habits usually outweigh the minor damage they cause, making them beneficial insects in the landscape.
The Nature of Earwig Damage to Trees
When earwigs feed on living tree parts, the resulting damage is typically superficial and cosmetic. They chew irregular holes in leaves, often leaving a tattered appearance that can be mistaken for slug or caterpillar damage. This feeding is usually concentrated on softer tissues, such as new growth, tender shoots, and flower petals.
On fruit trees, damage is usually confined to the surface of soft fruits like apricots, peaches, and berries, appearing as shallow gouges. Importantly, earwigs do not typically feed on hard fruits like apples or bore into the bark or cambium layer of a tree. For a mature tree with a large canopy, the loss of some leaf tissue or minor fruit blemishes does not affect its long-term health or survival.
When Earwigs Become a Significant Horticultural Problem
While mature trees usually tolerate earwig activity, specific circumstances can make the insects a serious horticultural concern. The most significant risk is to young, newly planted saplings or seedlings. On these small plants, earwig feeding on tender shoot tips or primary leaves can stunt growth or even kill the plant entirely.
A high-density infestation can also overwhelm established plants, especially in commercial settings where aesthetic quality is paramount. Extremely large earwig populations feeding on high-value ornamental flowers or fruit crops can lead to substantial economic loss. For instance, they may feed on corn silks, preventing proper pollination and kernel development. In these concentrated scenarios, the pest behavior supersedes their beneficial predatory role, requiring intervention.
Practical Steps for Earwig Management
The most effective approach to managing earwigs involves modifying the environment to make it less hospitable. Since earwigs seek dark, cool, and moist places during the day, reducing their hiding spots is the primary step. This includes removing debris, loose boards, leaf litter, and excessive ground cover near the base of the trees. Proper irrigation techniques, such as using drip systems, can also help by limiting surface moisture and humidity in the soil area.
Mechanical trapping provides a non-toxic method for reducing populations without chemical sprays. Simple traps can be made from rolled-up newspaper or corrugated cardboard placed on the ground or tied to a tree trunk. Earwigs will enter these traps to shelter during the day, allowing them to be collected in the morning and emptied into soapy water. Exclusion techniques, such as applying a sticky barrier like Tanglefoot around the trunk of fruit trees, prevent earwigs from climbing up to access developing fruit.
As a last resort for localized problems, low-toxicity materials can be used to protect vulnerable plants. Diatomaceous earth (DE), a naturally occurring powder, can be lightly dusted on the soil surface. It works by physically damaging the earwig’s exoskeleton, leading to dehydration. Ultimately, a balanced management strategy prioritizing habitat reduction and physical trapping will protect vulnerable trees while preserving the earwigs’ beneficial predatory role.