Earwigs

Several growers in the Western district of Victoria have reported damage to young canola plants and suspect European earwigs (Forficula auricularia) are the cause. Both adults and young nymphs have been found in affected crops. In the past, European earwigs have been known to devastate patches of canola crops in parts of the western district, and they can be difficult to control with conventional insecticides.

European earwigs are an introduced species that have been spreading in southern agricultural areas, probably by transport in hay, machinery or household pot plants. They are an emerging pest of canola, mainly on heavier soil types. It is believed that their numbers have increased in recent years due to intensive cropping and stubble retention, which improves the habitat for earwigs.

Adult European earwigs range from 12-20 mm long, are smooth and shiny dark brown in colour with pale yellow legs. They have distinctive “pincers” that protrude from their rear end and look very similar to native earwigs, which are commonly found around household leaf litter. Native earwigs rarely damage plants and are generally not significant pests.

European earwigs are nocturnal (therefore monitoring should be conducted at night) and shelter in dark spaces, such as under trash or cracks in the soil, during the day. They feed on the developing leaves of seedlings, slowing down plant development, and in some cases killing the plants. Irregular shaped holes are typical of earwig feeding. They can also chew through canola pods, causing seed development to stop, and contaminate windrows at harvest time.

European earwigs tend to only become a problem if populations become large. Reducing stubble residue may lead to a decrease in earwig numbers. The burning of stubbles in paddocks known to harbour earwigs has been shown to give satisfactory control but this has limited application as it can lead to wind erosion.

A reminder that it is important to know the difference between this species and native earwigs, particularly the common brown earwig (Labidura truncata). The common brown earwig is predatory, feeding on soft-bodied insects, such as caterpillars, redlegged earth mites and lucerne flea. It can be distinguished by the presence of an orange coloured triangle behind the head on the elytra or ‘wing-case’.

For further information and for images of European earwigs and native earwigs, click here.