by W.S. Cranshaw* (7/14)
- The common earwigs found in Colorado are an introduced insect that arrived in the state during the 1950s.
- Occasionally, earwigs damage soft parts of plants. However, the main food of earwigs is insects, including plant pests such as aphids.
- Earwigs like to hide in dark, tight-fitting areas during the day and often become nuisance problems as a result.
- Earwigs can be trapped in rolled-up, moistened newspapers.
- Preventing earwig movement into homes is best achieved by insecticide barrier treatments around house foundations.
The European earwig is an insect migrant from Europe that was established in the eastern United States around 1907. This insect rapidly spread across the United States and has occurred in Colorado since the 1950s.
The European earwig is about 5/8 inch long and brown with a reddish head. Young earwigs are similar in appearance to adults but smaller. A distinctive feature is the pair of prominent forceps at the rear of the body. Those of the male are more strongly curved than those of the female.
This is the only earwig found throughout most of Colorado. In the extreme southern areas of the state, a second species may be seen: the ring-legged earwig, readily identified by a band on the forelegs.
Earwigs are a common nuisance both indoors and out. During the day they hide in almost any dark, confined space, particularly if it also is rather moist. Typical indoor hiding places are under rugs or potted plants, in stacks of newspapers, and similar locations.
Outdoors, they commonly are found under rocks or stacked wood, in eartips of sweet corn, and under various kinds of debris. Peak problems with earwigs in Colorado tend to occur from mid-July through mid-September.
Earwigs are active at night and feed on a wide variety of materials. They occasionally cause injury to leafy plants such as lettuce and some flower blossoms. They often are associated with injuries caused by other insects. For example, leaves curled by aphids and holes in fruit are favorite hiding places for earwigs.
Earwigs mainly are a nuisance pest. Their reputation is made worse by the widespread fear that many people have regarding these insects. Several tales exist concerning alleged damage of earwigs: how they like to crawl into ears or how the forceps cause a painful pinch. These stories have little basis in fact, although earwigs have been known to cause a mildly painful bite when sat upon or handled.
Overall, earwigs may actually be considered beneficial — they feed on many plant pests, such as aphids, mites and insect eggs. Earwigs have been used for biological control of some plant pests. However, there are situations where control of earwigs is desired.
Managing earwigs is best achieved by combining several measures.
Many earwigs can be trapped which may help reduce numbers. Traps can be of various designs but should produce dark hiding areas that the earwigs will seek out for daytime shelters. Rolled corrugated cardboard can be very effective, as can rolled or crumpled newspapers. Furthermore, the addition of some food bait within the shelter can greatly improve the use of a trap by earwigs. Wheat bran and wheat germ are among the baits that have been effective in CSU trials. Such traps should be collected every 2-3 days, bagged and the captured earwigs discarded.
Certain oil-based baits are also effective traps. Vegetable oil or fish oil placed in a small cup sunk into the ground will be visited by earwigs. Keep the level of the oil at least an inch below the surface, forcing the earwigs to crawl deeply into the cup. Many earwigs may be attracted into oil-baited cups and drown.
Modifications of the area around the home also may reduce nuisance migrations into the home. Clear the area next to the home of sheltering debris (including mulches) used by earwigs, particularly near likely points of entry (doorways, window wells). This may be particularly effective if the an area is also relatively dry, denying moist shelters sought by earwigs. All cracks around doors and windows should also be sealed to prevent entry. Insecticides applied as barrier treatments to exterior near points-of-entry may supplement the effectiveness of these measures.
|Table 1. Insecticides recommended to control earwigs outdoors.|
|bifenthrin||Ortho Home Defense Max, Ortho Ortho-Klor, K-Gro Home Pest Control, Ortho Max Lawn & Garden Insect Killer, others|
|carbaryl||Sevin, many baits|
|deltamethrin||Hi-Yield Turf Ranger, Bonide Termite & Carpenter Ant Dust, Green Light Many Purpose Dust, others|
|lambda-cyhalothrin||Spectracide Triazide Soil & Turf Insect Killer, Ortho Bug Stop Home Insect Killer, others|
|permethrin||Ace Soil and Turf Insecticide, Bonide Eight, ferti-lome Indoor/Outdoor Multipurpose, Hi-Yield Indoor/Outdoor Broad Use Insecticide, Ortho Bug-B-Gon Max Garden Insect Dust, many others|
Insecticides can be applied in a variety of ways, depending on the situation. Several insecticides (Table 1) may be used as sprays, applied around flower gardens, building foundations or harborage areas where earwigs hide during the day. Some of these (e.g., Sevin, permethrin) have label use instructions that also allow some uses around fruit and vegetables. Applications made later in the day may be most effective since earwigs are active at night.
Bait formulations containing carbaryl (Sevin) as the active ingredient are also effective. These are broadcast around the base of plants and are eaten by the insects. Bait formulations are generally considered a means of using insecticides that have more selective effects compared to sprays.
Spot treatments may be most appropriate for many situations. For example, earwigs may be controlled on fruit trees by treating the area around the base of the tree, killing earwigs that crawl across this barrier.
* Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management. 1/00. Revised 7/14.
Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.
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