Earwig: Is it garden friend of foe?

The most common earwigs here are not Northern California native insects
 -- they're from Europe. (Photos courtesy Baldo Villegas)

This insect won't eat your brains, but loves seedlings and aphids

By Debbie Arrington

These invasive insects make people scream. Although they look the part, they won't eat your brains.
But there are two sides to earwigs.

Yes, they are voracious; these little omnivores eat both bugs and plants. They can destroy seedlings, but they have a big appetite for aphids. That makes them both a bad guy and good guy in the garden.

Right now, earwigs are out in force in Sacramento, munching their way through strawberries and toppling sprouts on a nightly basis. They prefer to eat in the cool of the evening. By day, they hang out in moist mulch, inside pots or other nesting places.

They rank among the most recognizable insects in the garden. They have (relatively) large pinchers at their tail end that they use for fighting. The male's pinchers are curved like forceps; the female's pinchers are straighter.

Munch, munch, munch -- an earwig in a rose.

According to University of California Integrated Pest Management program, the most common species in Northern California is the European earwig, Forficula auricularia. It's dark brown and almost an inch long. This invasive species arrived here sometime in the early 1900s and has been a pest ever since.

What does it like to eat? According to UC Cooperative Extension master gardeners, you should be concerned if you grow vegetables, herbaceous flowering plants, sweet corn, or plants with soft fruits such as strawberries and apricots.

They can seriously damage seedling vegetables as well as berries. They chew holes in annual flowers (especially zinnias) and munch corn silk, which can prevent the ear from forming kernels

The name "earwig" comes from the Olde English words for "ear beetle." People believed that this long, thin insect could crawl inside their ear and tunnel into their brain to lay its eggs.

Of course, it does no such thing. Earwigs lay their eggs underground in some moist spot. That's also where they hibernate. They have only one generation a year. During summer heat, they tend to disappear -- back into the mulch.

On roses, earwigs are more likely to be going after aphids than snacking on the blossoms. They also eat mites and insect eggs, making them more beneficial than detrimental.

Earwigs tend not to be a problem in California native gardens; it's too dry. They thrive in lush, shady and well-irrigated conditions, like English gardens back home.

Pesticides such as bug baits aren't very effective against earwigs. The best way to handle too many earwigs is to think like an earwig. Where would you hide?

Manage them by eliminating hiding places; that's where they are during the day. They like to hang out in weedy areas or under thick vines. Move pots around. Pick up boards or stepping stones.

Trap them. Set up several traps around the yard (especially near areas under attack), along fence lines or near shrubs and ground covers. The most effective trap: A shallow can with a little oil. Earwigs love tuna or fish oil or the scent of bacon grease. The master gardeners suggest using low-sided containers such as tuna or cat food cans. Sink the can down in the ground, so its top edge is at soil level. Place 1/2-inch vegetable oil in the bottom of the can, preferably with a drop of bacon grease or fish oil.

Each morning, check the traps. Dump the earwigs and replenish the oil.

Earwigs also go for paper traps, made of rolled-up newspaper or brown corrugated cardboard. They go after all sorts of short tubes, such as bamboo tubes or short pieces of hose. Check these traps and shake out any earwigs into a bucket of soapy water.

Don't worry; earwigs look mean but they don't harm humans.

For more information on earwig control, check out these UC IPM quick tips: http://ipm.ucanr.edu/QT/earwigscard.html