Earwigs are both beneficial and a pest

By Melanie Mathieson
Gardening Guru

Due to the mild winters of recent years, earwigs have successfully migrated north and established themselves in the yards and gardens of northwestern Ontario. By far, earwigs seem to be the insect that makes humans cringe the most. When mentioned in conversation, even those that have never seen an earwig have a look of disgust on their face and a comment to match.
But before we are too negative about earwigs, we must review their positive side. Yes, earwigs do have some redeeming qualities. They clearly walk the line between being a beneficial garden insect or a garden pest. Most people do not realize that earwigs are omnivorous, which means they eat both meat and plants. In the insect world, this means that earwigs also eat other insects, their eggs and larvae. The earwig is a scavenger, roaming the yard and garden for delicacies like aphids, mites, nematodes, slugs and their eggs, other soft bodied insects and decaying plant matter. If none is found then they will seek their food source from live plants, which is when the gardener notices the damage and complains about the destruction they cause.
Earwigs will eat ornamental and vegetable plant leaves and tender roots, particularly dahlias, marigolds, zinnias, sunflowers, grasses, butterfly bush, hollyhocks, lettuce, strawberries, potatoes, roses, bean and beet seedlings, berries, apricots, peaches as well as the silk of sweet corn. Earwigs are also notorious for eating holes in buds and blooms of Clematis while leaving the foliage alone. This season a few gardeners have described this problem to me.
When serious feeding damage occurs, leaves will have numerous, small, irregular holes, giving the plant a ragged appearance. As this type of damage can often be mistaken for the same type of damage caused by other pests such as slugs, it is important to be sure you’ve identified the real culprits, by looking for feeding earwigs on your plants after dark.
Earwigs are brown to black, glossy flattened insects that measure 1/2 to 1 inch long. They have a pair of curved pincers or forceps emerging from the tip of the abdomen. They use their pinchers for hunting and securing other insects. Adults may or may not have wings, but they rarely fly. Earwig larvae resemble adults because they develop from egg to adult through gradual metamorphosis, with four to five nymphal instars or stages, similar to grasshoppers.
During the spring or autumn, females lay 20 to 50 smooth, oval, pearly-white or cream-colored eggs in the upper two to three inches (5 to 7.6 cm) of soil. They are unusual among insects in that the female fusses over her eggs and nymphs, and uses her pincers to protect them. Most species have one generation a year, but in milder climates, some remain active all year. Both eggs and adults overwinter in the soil or under garden debris, stones, and boards. Adults and the young require moisture to live which is why they are found in damp areas. Earwigs are unable to crawl long distances, but often hitchhike in laundry baskets, cut flowers, luggage, newspapers, lumber, baskets of fruits and vegetables, automobiles, etc.
Usually the damage to plants caused by earwigs is minor, unless their populations are high. As earwigs hide in cool, moist places during the day and feed at night, good housekeeping practices in the yard and garden can go a long way in reducing populations of earwigs. Here a few simple tips for prevention.
•Clean up garden debris and organic mulches, especially around foundations, since these moist areas serve as daytime hiding spots for earwigs.
•Spread dry gravel as mulch next to foundations.
•Earwigs are attracted to lights, so eliminate or reduce lighting around foundations.
•Remove leaf litter, large stones, dead wood, wood piles, and mulches.
•Keep shrubs neatly trimmed to allow for light penetration and air circulation, especially near the base of the shrub.
•Discourage and reduce entry into buildings by caulking and repairing, cracks and crevices, and checking door thresholds, windows and screens for a tight fit.
Although you may be disgusted by earwigs, remember they are considered beneficial insects so they should only be treated as pests when their damage becomes excessive. Here are some helpful tips to control earwig populations already established in your yard or garden:
•Homemade trapping mechanisms are most effective and can be achieved with various methods that provide a dark, damp hiding place. If you use any of the methods described below make sure to empty your traps each morning and dispose of the earwigs by first dumping in hot soapy water and then putting in a sealed plastic bag before placing in the garbage bin.
•Make traps from rolled-up newspapers, cardboard tubing or cardboard filled with straw or crumpled newspaper, tape shut at one end, and then dampen slightly. Place them near plants in the late afternoon or evening and empty or replace each in the morning.
•You can also make a trap by filling a flowerpot with damp crumpled paper; then turn it upside down propping one edge up with a stick. Earwigs will crawl into the newspaper to hide. Empty or replace each morning.
•The thrifty gardener recycles an old, leaky hose by cutting into lengths of a foot or so long and scattering around the garden. Each morning immerse the hose in hot soapy water to extract the earwigs and place back in the garden.
•Cardboard boxes (as simple as a cereal box or a shoe box) turned open side down or with holes cut in the sides and the lids intact, dampened and placed near plants make great traps. Simply throw away or empty and reuse until no longer functional. You may see tips using this method and indicating to use oatmeal or bran in the box as bait. This is not necessary as it works just as well without the bait. Dampened sheets of corrugated cardboard work too but there is less space to catch earwigs.
•Fill tuna cans with 1/4 inch of oil, preferably fish oil, but any type of edible oil will work (vegetable, safflower, olive, etc.) and sink them into the ground near plants. Empty them every day. I caution you on the use of this type of trap as the smell of fish oil may also attract other pests like raccoons, bears, dogs, cats, etc. So you may consider this method as more of a last resort. Like slugs, earwigs are also attracted by beer, so it can be substituted for the oil.
•Sprinkle a 2-inch-wide circle of diatomaceous (crushed diatom fossils shells) earth around beds or the base of plants; reapply after rain. This can be purchased at feed or nursery supply stores and is an excellent source of calcium for the garden.
•Place a light-colored cloth beneath an infested plant and shake or tap the branches. The earwigs should fall onto the cloth and than can be disposed of.
•The earwig’s only insect predator in North America is the tachinid fly. Attract this fly by planting alyssum, calendula, dill, and fennel.
•Place a sticky barrier, such as Tanglefoot ™, sticky tape or even petroleum jelly, at the base of woody plants. Earwigs are crawlers and they’ll get stuck in the sticky mess before they can get up the tree or shrub to cause damage.
•If absolutely necessary, insecticides labeled for crawling insects can be used. Apply in the evening, before feeding begins. In addition to homemade traps, commercial earwig traps are available at nursery supply stores. Some versions have pesticides in them so read the label carefully and use with caution.
•If found indoors, remove by vacuuming.
Hopefully you have a new appreciation for the benefits that earwigs can provide to a garden and not just the negative side of this insect. If you still need to get rid of them, then I hope these tips are useful to you.