Earwigs: A case of "Ewwww"

Posted by: Alison O'Connor, CSU Extension in Larimer County

There are certain insects that seem to like to jump out at you and say "Boo!" Earwigs are one of those--they hide in small spaces and make their appearance known by quickly crawling away. And they always seem to show up in unexpected spots--like tucked in the bloom of a peony. The species we see in Colorado is the European earwig (Forficula auricularia). Even though my BFF Carl Linnaeus named this species back in 1758, it doesn't mean I have to like them.

European earwig (photo courtesy of Whitney Cranshaw)

Earwigs, characterized by their rear-end "pincers", cause damage to a wide array of plants, including ornamentals and edibles. Their pincers, by the way, are not dangerous--they use them for mating. These insects pose no threat to humans (except for increasing your heart rate when you come across them in damp, dark areas), but they are a nuisance both indoors and out. It has been reported that if handled, their bite is mildly painful. So don't handle them. Why would you want to handle them??

Boo! Earwigs in a peach.
(photo courtesy of University of Nebraska Dept of Entomology)

It's been a darn good year for earwigs. At the farmers' market, it seems we get at least one or two questions each week on "Something is eating my plants, but I don't see any bugs!" That's because earwigs are nocturnal feeders. They come and munch on your garden buffet at night. And mid-July to mid-September is the prime season to see damage. Why are they so rampant this year? My guess is it's because of our wet weather.

Earwig damage on common mallow
(photo courtesy of Whitney Cranshaw)

Earwig injury to peaches
(photo courtesy of Utah State University Extension)

So if you're seeing feeding injury on plants, but aren't sure what might be causing it, try setting out earwig traps. This is a fun and enjoyable project for the entire family. You can use rolled up, moistened newspaper or corrugated cardboard. Place in the garden and unroll in the morning to see if you caught any (or just throw in the trash if you're squeamish). Another option is to put a small cup of oil (vegetable, canola) in the garden, in a shallow hole. Make sure the oil is at least 1" below the soil surface. The earwigs will fall into the cup and drown in the vat of oil.

Earwig newspaper trap
(photo from www.freshmanfarmer.com)

Dr. Whitney Cranshaw, our state entomologist, is doing some research this summer using various oils and other condiments. For now he recommends using oil (vegetable, canola, mineral) and even add a dash of soy sauce. A couple years ago he caught over 500 earwigs in one evening using his canola-oil trap!

Canola oil earwig trap. In one evening,
Dr. Cranshaw caught 535 earwigs!

If you're not into trapping, consider cleaning up around the house or in the vegetable garden where debris and mulch may be piled. Seal cracks near doors and windows. Insecticides can be applied as a barrier. For more information on European earwigs and the control options, refer to CSU Extension Fact Sheet #5.533.