The Earwig: A Best Friend to the Garden or a Health Hazard?

Is it best for a garden’s health – or a gardener’s health – to eradicate earwigs, or to encourage them? How can people help an earwig population to thrive? How could one get rid of an earwig infestation?

The Earwig on its Best Behaviour

The earwig, like every adult insect, has a head, a thorax with six legs, and an abdomen. The two long antennae reach out at about a 45 degree angle to the front and sides, rather than upwards to the front. The most remarkable feature is that the abdomen ends as a pincher or “forceps”. It usually hides its wings. Its overall length varies from one-quarter to one inch.

An earwig starts life as an egg in an underground nest within a couple of inches of the surface. It will hatch into a nymph – immature and small, but shaped like an adult. After about two weeks of tender care from the mother, the nymph will begin foraging for food. It will reach adulthood after five molts. Eventually it will mate and start the next generation, then die after about a year.

 

Starting at dusk, an earwig will eat live or decaying plant material, decaying meat, and some insects. It will hide in moist, dark places during the day.

If a gardener notices damage to a plant, there are often many potential culprits. Blame slugs if a slime trails are left behind; earwigs do not secrete slime. Squirrels and other mammals, as well as birds and a variety of insects, enjoy vegetables or flowers.

An earwig will not harm people directly; it does not spread disease by biting or stinging; it is not a threat to human health. Despite the name, it will not crawl into people’s ears; nor will it eat their brains. It may pinch the skin or emit a nasty smell. In fact, it can help reduce the population of other pests by eating aphids, adult or larval insect, or the eggs of insects or slugs.

To help maintain an earwig population, simply composting plant material will provide both shelter and food. If the compost is kept away from the main garden area, and has enough sustenance, earwigs will not be inclined to eat more vegetation from the garden. The fully-composted soil should have very few earwigs, since they prefer the upper layers where their food is still decaying.

The Earwig as a Pest

An earwig living indoors is a sign of excessive dampness: possibly a plumbing problem in the basement or under the kitchen sink; perhaps some vegetables are rotting in the cellar; maybe damp newspapers or rags are serving as shelter. It is better to fix the problem than fixate on killing the messenger.

Several steps can be taken to reduce the number of earwigs in a garden, without resorting to pesticides. These include:

  • Eliminate above-ground nesting areas, such as piles of leaves, overturned pots, and loose rocks.
  • Add a seasonal bird feeder and bird bath to encourage these predators to eat the garden insects.
  • Remove damaged fruits or vegetables, since earwigs will be attracted to rotting food.
  • Turn over the soil at the start and end of the growing season, to expose eggs and adults to the surface.

Trapping earwigs takes a bit more work. The trap is a loosely-rolled newspaper, soaked with water, and placed on the ground where the earwigs have been. Left overnight, the trap becomes a home to vagrant earwigs. The trap can be sealed in a heavy plastic bag; or the earwigs might be shaken into soapy water for a quick and merciful death.

Another type trap is an open-topped can, buried to the rim in soil, and partly filled with vegetable oil. Perhaps the simplest and best example is a sardine can. Remove the sardines, add some more oil, and push it into the earth.

Diatomaceous earth kills earwigs (and some other insects) because it cuts the chitinous exoskeleton as the insects crawl over it. The insects slowly dehydrate. This method can serve as a literal “line in the sand”, to keep earwigs away from an area. Or the diatomaceous earth can be spread across the whole garden.

In the most extreme cases of infestation, chemical pesticides may be needed to control the earwig problem. Local regulations vary! Health Canada’s article notes that carbaryl, propoxur or pyrethrin may be appropriate if applied and handled properly. Any of these can harm children or pets; each should only be used as directed. As well, the outdoor insecticides are most helpful in the spring months.