European earwigs

Agronomist, Steve Dickson (CropPlus Agronomy), reports that European earwigs (Forficula auricularia) have been found attacking several emerging canola crops west of Inverleigh, in the Western district of Victoria. Steve says all paddocks have similarities; high organic matter, clay-loam soils and minimum tillage. Both adult and juvenile earwigs have been observed, perhaps indicating a second generation. In some paddocks, insecticide-treated seed appears to be withstanding earwig attack. Agronomist, Craig Drum (Tatyoon Rural), has observed high numbers of European earwigs in several canola paddocks near Lake Bolac, also in the Western district of Victoria. Craig says some paddocks have suffered significant damage and require re-sowing.

European earwigs are an introduced species that has been spreading in southern agricultural areas. It is believed earwig numbers have increased in recent years due to intensive cropping and stubble retention, which increases the suitable habitat available. European earwigs are mainly found on heavier soil types. Besides canola, they can also damage cereal and legume crops. They feed on the developing leaves of seedlings, slowing down plant development, and in some cases killing the plants. Typical feeding damage is shredded leaf tips and/or irregular holes in leaves. They can also chew through canola pods, causing seed development to stop, and contaminate windrows at harvest time.

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. 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’.

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. 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. Insecticide baits can be used against European earwigs. Baits can be prepared by mixing chlorpyrifos with sunflower oil and then adding this to cracked wheat or sorghum. Steve says baits have been used in some paddocks this year.

For further information and images of earwigs, click here.