Jeffrey Hahn, Asst. Extension Entomologist
Immature earwigs were have been seen in gardens recently and will soon turn into adults. Many areas of Minnesota experienced high earwig numbers last year. Be on the watch for them in your garden this summer. Earwigs are about 5/8 inch long, with a flat, reddish brown body and very short wings. They look like a cockroach or a rove beetle but are distinctive because of the pair of pinchers (cerci) on the tip of their abdomen. Nymphs are similar to adults except they are smaller and generally lighter in color.
Earwigs are most active at night and like to hide during the day in dark, tight, damp areas, like under potted plants, cracks between bricks and pavers, and on plants in buds and folded leaves. Earwigs are scavengers, feeding on damaged and decaying plant matter as well as weakened or dead insects and other small organisms. Earwigs can also feed on healthy plant material. This is when they can become a problem in gardens.
Earwigs can damage flowers, like dahlias and marigolds, chewing irregular holes in flower blossoms and in leaves. They are also reported to attack various vegetables, corn silk, and seedlings. Some of this damage can be confused with slug feeding. However, slugs leave a slime trail while earwigs do not. If you are not sure what is causing the damage you are finding, go outside at night with a flashlight check under plants for earwigs and other pests.
To reduce the number of earwigs around your garden, clean up debris that earwigs can hide under, such as leaves, plant debris, bricks, piles of lumber, and similar things. It can also be useful to thin out or remove mulch. You can also set out rolled up newspapers to trap earwigs. Put them into your landscape or garden during evening. In the morning shake the traps above a pail of soapy water to remove the earwigs.
Minimize excess moisture in the landscape. Be sure that the landscape has good drainage and that irrigation systems are working properly. A good strategy when watering is to irrigate more thoroughly and deeply but less often so the surface of the soil remains drier.
You can also protect plants with an insecticide application. An effective method is to treat the surrounding mulch where the earwigs are hiding. Use a drench, e.g. lambda cyhalothrin or carbaryl for this. You may need to attach the product to a hose to get sufficient volume. You may also be able to protect individual plants by applying a spray, e..g. permethrin, deltamethrin, or acetamiprid or a dust, e.g. permethrin or deltamethrin, to plants when damage is first noticed.