Earwigs do not kill trees. They lack the mouthparts and behavior to bore into bark, girdle trunks, or destroy the woody tissue that keeps a tree alive. What earwigs can do is damage soft fruit, nibble flowers, and create tiny wounds that let fungal diseases take hold, but even these problems are limited to certain crops and certain times of year. In many orchards, earwigs are actually considered beneficial because they eat aphids and other pests that cause far more harm than the earwigs themselves.
What Earwigs Actually Do on Trees
The European earwig, the species responsible for nearly all earwig complaints in gardens and orchards across North America, Europe, and Australia, is an omnivore with a wide diet. It eats soft plant tissue, decaying organic matter, and a surprising range of small insects. Research in orchards and vineyards describes this species as having significant “diet breadth,” feeding on vegetables, grains, flowers, and fruits while simultaneously preying on aphids, mites, and other soft-bodied pests across crop types.1Journal of Integrated Pest Management. Biology and Management of European Earwig in Orchards and Vineyards That dual identity is central to understanding why earwigs show up on your trees without actually threatening them.
Earwigs do not chew through bark. They do not tunnel into wood. They do not attack roots. The kinds of insects that genuinely kill trees, such as bark beetles, emerald ash borers, and ambrosia beetles, have specialized anatomy for boring into living or dead wood. Earwigs have short, broad mandibles designed for tearing soft material. They gravitate toward fruit that is already ripening, flowers that are open and accessible, and the soft bodies of insects smaller than themselves. A healthy tree trunk is simply not on the menu.
Fruit Damage Is Real but Limited
Where earwigs do cause legitimate problems is on the fruit itself. In sweet cherry orchards, researchers found that excluding earwigs from cherry bunches reduced fruit damage by roughly a fifth to a third depending on the variety.2PubMed Central. Cherry damage and the spatial distribution of European earwigs, (Forficula auricularia L.) in sweet cherry trees The damage is concentrated on the fruit surface and stem, not the branch or tree structure. Earwigs tend to cluster inside dense fruit bunches, and varieties with larger, tighter bunches had more damage. Some cherry varieties had stems that were far more prone to earwig feeding than others, with one variety showing stems 40 times more likely to be damaged than another.
In citrus, earwigs climb tree trunks at night to feed, but the window of vulnerability is narrow. Surveillance in California citrus groves showed that by the time earwig numbers peaked in early summer, the fruit had already grown past the size where earwig feeding could cause meaningful harm.3Journal of Economic Entomology. The European earwig Forficula auricularia (Dermaptera: Forficulidae) in California citrus: a sampling method, population surveys, and description of earwig movement into the tree canopy The timing matters: earwigs can damage small, tender fruitlets and flowers, but once fruit firms up and grows, it becomes much less attractive to them.
In a Mediterranean organic citrus orchard, researchers tracked what happened when earwigs were present versus excluded from trees over an entire growing season. Earwigs did reduce flower survival early on, but that effect disappeared once the trees naturally shed excess flowers and fruitlets on their own. When the researchers measured final fruit yield, there was no difference between trees with and without earwigs.4Biological Control. Friend or foe? The role of earwigs in a Mediterranean organic citrus orchard The tree didn’t care about the earwigs, because the nibbled flowers were ones it would have dropped anyway.
The Brown Rot Connection
One indirect way earwigs can harm fruit trees is by opening the door to fungal disease. Observations in English apple orchards in the late 1940s showed a tight link between earwig damage and brown rot, a common fungal disease that causes fruit to decay. Earwigs create shallow holes in apple skin, and those holes become infection points for the brown rot fungus. When researchers wrapped tree trunks with insecticide-soaked bands to trap earwigs before they could climb into the canopy, the banded trees had less brown rot than the control trees. A broader survey of picked fruit confirmed a close correlation between the degree of earwig damage and the amount of brown rot present.5Annals of Applied Biology. Observations on Brown Rot (Sclerotinia fructigena) of Apples in Relation to Injury Caused by Earwigs (Forficula auricularia)
This is worth understanding clearly: earwigs are not spreading the fungus themselves. They are creating tiny wounds in fruit skin that the fungus exploits. Many other things create similar wounds, including hail, bird pecks, wasp stings, and twig abrasion. Earwigs are one contributor among many. And again, the damage is to fruit, not to the tree. Brown rot can ruin a harvest, but it does not kill the tree carrying that harvest.
Why Earwigs Often Help Trees More Than They Hurt Them
The most counterintuitive finding in the earwig literature is that these insects are frequently beneficial in tree systems. Their appetite for aphids, which are genuine tree pests capable of stunting growth, curling leaves, and transmitting plant viruses, often outweighs the cosmetic fruit damage they cause.
In canola crops, a study found that earwigs caused noticeable feeding damage to seedlings early in the growing season. But by the end of the season, plants in areas where earwigs were present actually had more biomass than plants without them, because the earwigs had been eating aphids throughout the growing period. The researchers noted a critical behavioral pattern: earwigs did not switch to feeding on plants until all nearby aphids had been consumed.6Journal of Applied Entomology. The dual role of earwigs (Dermaptera) in winter grain crops in Australia In other words, earwigs prefer animal protein when it is available. Plants are the fallback diet.
In the citrus orchard study mentioned earlier, aphid infestations were consistently less severe on trees with earwigs than on trees without them, and aphid density dropped as earwig numbers increased.4Biological Control. Friend or foe? The role of earwigs in a Mediterranean organic citrus orchard Apple orchards show a similar trend. Researchers who introduced earwigs into apple tree canopies to control woolly apple aphid found that, in general, trees with more earwigs had fewer aphid colonies, though the biological control effect alone was not enough to eliminate the aphid problem entirely.7Entomologia Experimentalis et Applicata. Control of Woolly Apple Aphid (Eriosoma lanigerum) by Augmenting Earwigs (Forficula auricularia) in the Canopy of Apple Trees Earwigs are part of the pest control picture, not the whole picture.
This is why integrated pest management researchers argue for maintaining earwig populations in orchards rather than eliminating them. Broad-spectrum insecticides that wipe out earwigs can remove a layer of natural aphid control, sometimes making overall pest problems worse.8Biological Control. Non-target consequences of insecticides used in apple and pear orchards on Forficula auricularia L. (Dermaptera: Forficulidae)
Earwigs as Predators of Actual Tree-Killing Insects
Here is where the story gets genuinely interesting for anyone worried about tree health. Ambrosia beetles are among the insects that can seriously harm or kill trees. They bore into wood and introduce fungi that block the tree’s vascular system, causing branches or entire trees to die. Laboratory experiments have shown that earwigs actually prey on ambrosia beetles, suggesting they could play a role in controlling populations of these genuinely destructive pests.9Wiley Online Library. Earwig preying on ambrosia beetle: Evaluating predatory process and prey preference The irony is hard to miss: the insect people fear is killing their trees might be eating the insects that actually could.
This predatory behavior extends beyond ambrosia beetles. Because earwigs are active at night when many other predatory insects are not, and because they can survive on alternative food when prey is scarce, they fill a pest-control niche that more specialized predators leave open. Pairing earwigs with daytime predators like ladybugs or parasitoid wasps can strengthen biological control across the full 24-hour cycle and across seasons when prey populations fluctuate.1Journal of Integrated Pest Management. Biology and Management of European Earwig in Orchards and Vineyards
How Earwigs Use Trees
Understanding earwig behavior on trees helps explain why so many people assume they are causing damage. Earwigs are strictly nocturnal. In citrus groves, monitoring showed activity only between sunset and sunrise, with earwigs moving both up and down tree trunks throughout the night.3Journal of Economic Entomology. The European earwig Forficula auricularia (Dermaptera: Forficulidae) in California citrus: a sampling method, population surveys, and description of earwig movement into the tree canopy During the day, they retreat into dark, tight spaces: bark crevices, rolled leaves, mulch at the base of the tree, or gaps in fruit clusters. If you peel back loose bark and find a cluster of earwigs, it is easy to assume they are eating the tree. They are not. They are sleeping.
Earwigs aggregate for reasons related to their social behavior. They release pheromones that attract other earwigs to the same hiding spots, which is why you tend to find them in groups rather than singly. This aggregation is harmless to the tree but alarming to the gardener who discovers 30 earwigs under one piece of loose bark.
Their seasonal patterns also matter. Earwig populations typically follow one or two breeding cycles per year, depending on climate. Both single-brood and double-brood populations show fairly predictable timing based on accumulated warmth over the season, allowing researchers to forecast when various life stages will appear.10Wiley Online Library (Agricultural and Forest Entomology). Optimizing biocontrol using phenological day degree models: the European earwig in pipfruit orchards For fruit growers, this means earwig damage risk peaks during specific windows, not all season long. For home gardeners, it means the late-spring and early-summer explosion of earwigs around trees is temporary.
When Earwigs Are Actually a Problem Worth Managing
If you grow soft fruit, especially cherries, apricots, or stone fruit prone to skin damage, earwig feeding can be a legitimate nuisance. The same is true for certain ornamental flowers like dahlias and zinnias, where earwigs chew petals at night. In these situations, targeted management makes sense. But “targeted” is the key word. Blanket insecticide applications harm earwig populations without distinguishing between the ones on your cherry tree and the ones eating aphids on your apple tree next door.
The most effective and practical monitoring tool is a simple corrugated cardboard trap wrapped around the trunk. Research comparing various trap designs found that cardboard outperformed both black and translucent plastic alternatives. Traps placed on the main trunk caught more earwigs than traps on branches, and there were diminishing returns beyond about 30 centimeters of trap length. Lures and baits mostly did not help, with the exception of fish sauce, which inconsistently boosted catches. Leaving traps in place longer increased captures, possibly because earwig aggregation pheromone accumulated on the cardboard over time.11Journal of Economic Entomology. Evaluating trapping methods to increase earwig capture in temperate tree fruit crops
These traps serve double duty. You can use them to monitor how many earwigs are present and decide whether action is needed, or you can use them as a mass trapping tool by collecting and removing earwigs daily during the vulnerable fruit-ripening window. Other physical barriers include sticky bands around trunks, which block the nocturnal climb into the canopy, and removing ground-level debris and mulch near the trunk where earwigs shelter during the day.
The broader point is that earwig management in a tree context is about protecting specific fruit at specific times. You are managing a cosmetic issue with your harvest, not saving the tree from an existential threat.
Common Misconceptions About Earwigs and Trees
Several persistent myths deserve direct correction. The first is that earwigs bore into wood. They do not. If you see bore holes in your tree, you have a beetle problem, not an earwig problem. Earwigs may be sheltering in abandoned beetle holes, but they did not create them.
The second is that finding earwigs on a declining tree means they are causing the decline. Earwigs are attracted to moist, decaying organic matter. A tree that is already stressed, leaking sap, or developing fungal infections creates exactly the environment earwigs seek out. They are following the decay, not causing it. This is a classic correlation-versus-causation mistake, and it is one of the main reasons earwigs have such a bad reputation among gardeners.
The third misconception is that earwig populations need to be eliminated from the garden. Given their role in suppressing aphids and even preying on wood-boring beetles, a garden without earwigs may actually face worse pest problems. The evidence from multiple orchard studies consistently points toward keeping earwigs around and managing their access to sensitive fruit, rather than trying to wipe them out.
Winter Biology and What Extended Cold Means for Populations
Earwigs overwinter underground in burrows, and the length of winter has real consequences for the next generation. Research on earwig offspring reared through different winter durations found that eggs exposed to shorter winters hatched earlier and the resulting juveniles reached adulthood faster. Extended winters imposed lasting biological costs: females from long-winter conditions showed immune markers about 30 percent higher than those from short winters, suggesting their bodies were under greater physiological stress. Meanwhile, a different immune cell type was twice as high in short-winter females, but only when housed with unfamiliar individuals.12PubMed Central. Extended winters entail long-term costs for insect offspring reared in an overwinter burrow
What this means practically is that mild winters tend to produce earlier, faster-developing earwig populations, which could shift the timing of when they show up on your trees in spring. In regions where winters are becoming shorter due to climate change, earwig populations may emerge earlier and potentially overlap more with vulnerable early fruit development. For growers who rely on earwigs for biological control, the timing shift cuts both ways: earwigs might arrive in the canopy sooner, but so might the aphids they eat.