European Earwig

The introduced European earwig is the most common of several earwig species that can occur in citrus. Adults are about 0.75 inch long, reddish brown, and have a pair of prominent tail appendages (cerci) that resemble forceps. Most species have wings under short, hard wing covers, but earwigs seldom fly. Males have stout, strongly curved cerci that are widely separated at the base while females possess slender, straight pinchers that are close together. European earwigs use these cerci to protect themselves and to grab and hold prey. Immature earwigs resemble small, wingless adults. Ring-legged earwigs (Euborellia annulipes) may also occur and can be distinguished by their smaller size and banded legs. Ring-legged earwigs are not known to be a citrus pest and do not need to be managed.

Earwigs feed mostly at night and hide during the day. Common hiding places include bark crevices, mulch, topsoil, protected compact plant parts such as dried, curled leaves, and under trunk wraps. Females lay masses of 30 or more eggs in soil. First instar nymphs are whitish and remain in the soil until their first molt, after which they darken and begin emerging from the soil in search of food. Earwigs generally have one generation a year, but they can have two broods. At around six weeks after petal-fall, most earwigs have developed into adults. Eggs and nymphal stages are present from early spring through early summer, while adults can be active in the orchard year-round.

Earwigs feed on dead and living insects and insect eggs and on succulent plant parts. Earwig nymphs and adults will climb trees and feed on flower buds, leaves , and fruit of trees during the spring flush months (March through May). Nymphs tend to feed on plant material more than adults.

Earwigs can be very problematic on young trees with trunk wraps or cardboard guards, in which they reside. They climb the trees and feed on the new leaves. Large numbers of earwigs can defoliate trees.

The main economic damage caused by earwig nymphs and adults on fruit-bearing citrus occurs when they feed on very small, developing fruits in the one to four weeks immediately following petal fall. Thus, it is this in this short window of time after petal fall that treatment is most critical. Earwigs chew holes in the rind of young fruit, which causes large, depressed scars as the fruits mature. This damage can cause downgrading at the packinghouse. Earwig fruit damage can be difficult to distinguish from that of other chewing pests including katydids and orangeworms. Earwig damage is often near the calyx of the fruit and is irregular or rectangular in shape.

Citrus species vary in their susceptibility to fruit damage by earwigs. Vulnerability is higher in sweet oranges (e.g., Washington navel) and clementine mandarins such as De nules and Fina Sodea compared to C. reticulata mandarin fruit. Clementine mandarins have irregular, webbed scars). C. reticulata mandarin fruits (e.g., Tango) seem to be largely resistant to earwig damage.

If you suspect that earwigs are causing damage in young trees, lift and shake or sharply tap any trunk wraps and look for earwigs dropping to the ground, where they quickly scurry for cover. Remove trunk wraps when they are no longer needed for sunburn or rodent control, thereby reducing earwig numbers. Apply a treatment to the soil at the base of trees.

In mature trees, one to four weeks after petal fall when young fruit could be damaged, use a beating sheet or net to shake the trees and dislodge earwigs to determine if earwigs are infesting the trees. Additionally, use a stick or rake to sift through leaf litter and dirt clods around under the canopy of 10 to 20 trees per orchard to determine if earwigs are in the soil. Rolled up cardboard may also be used as earwig traps on tree trunks or branches to determine earwig numbers. Where damage to young fruit is occurring, foliar applications of insecticides with an air blast sprayer can be effective; however, only the most broad-spectrum insecticides reduce their numbers and these insecticides may affect natural enemies needed for other pests. It may not be necessary to control earwigs in C. reticulata (Tango) since they seem to be resistant to earwig damage. Soil treatments for Fuller rose beetle likely also reduce earwig numbers.