The European earwig (Forficula auricularia) is both a beneficial insect on wine grapes and a pest of table grapes.
All stages feed on small, soft-bodied insects such as small leafhopper nymphs and will scrape leafhopper eggs off of leaves. In fall, they feed to some extent on damaged grapes, and their presence in table grapes is not appreciated by some consumers.
On grapes produced for wine, they should be considered important generalist predators.
Adult earwigs are dark brown, about 1.5 cm long, with a pair of forcep-like appendages (cerci) at the rear of their elongate bodies. The anal forceps of females are long and straight, while those of males are curved.
Earwigs seldom fly, and the membranous hind wings usually remain folded under the short leathery forewings, exposing the abdomen. The four nymphal stages resemble the adults except that they are smaller and wingless.
Earwigs are largely nocturnal and hide during the day, often in large aggregations, in cracks and crevices or under bark. When disturbed they move quickly.
Adults overwinter in the ground in earthen cells. Clutches of eggs laid in cells in the top 5 cm of soil in the fall and spring are opened by females in spring to release the young nymphs.
Adults are semi-social and tend their young for a period of time after birth. Nymphs later disperse to secure locations under rocks, in crevices or under bark. Adults develop by mid-summer and there is only a single generation per year.
Earwigs feed at night on damaged fruit, tender plant tissue, small soft bodied insects and other foodstuffs. They rarely damage grape leaves.
Rolled up newspaper or cardboard, or flat boards placed on the ground, can be used to monitor earwigs. It might be possible to use these same refuges to enhance their numbers in wine grapes.
Earwigs are sensitive to most insecticides applied for the control of other pests of table grapes. For this reason, earwigs are a greater concern for organic table grape production. Commercial earwig baits are also available.
For more information about chemical control, see the Pesticides page.
Birds, large spiders, wasps and ground beetles prey on earwigs. Earwigs, in turn, feed on the eggs and small nymphs of leafhoppers and on other soft bodied insects.
Tillage in spring and fall will destroy some of the earthen cells. For table grapes, mowing, tillage, removal of loose bark from vine trunks and sanitation will remove hiding places and help reduce earwig numbers. They can be kept out of small plantings of table grapes by applying sticky tape or commercial Stickum® around trunks and posts.
Washing table grapes after harvest will help dislodge many earwigs. They are less likely to seek refuge in table grape varieties with loose, open fruit clusters.
