A number of earwig species are omnivorous. Their plant-feeding behaviour may result in plant damage but their predatory behaviour may also effectively control other crop pests.
Adults are 15 mm long, shiny black with a flattened body and a pair of curved pincers at the end of the body. Nymphs resemble adults but are wingless and paler.
The common brown earwig (Labidura truncata), which grows to a larger size (24 mm) and is lighter in colour than the black field earwig.
Wheat, sorghum, maize and sunflowers are the preferred hosts, but seedlings of most field crops are susceptible.
|Life cycle on maize||
The black field earwig normally feeds on decaying stubble in cultivation with all stages (adults and immatures) present during warmer months. In common with a number of earwig species, female black field earwigs lay eggs in a burrow in the soil and remain to care for the eggs and nymphs. Eggs hatch in 6-7 days at 29°C. The developmental time for five nymphal instars is about seven weeks in clay soils, longer in sandy soils. Nymphs develop into adult females or major or minor males. Longevity is about 20 weeks.
The black field earwig eats newly sown and germinating seed and the roots of crops, resulting in poor establishment. Feeding on secondary roots may cause the plants to fall over as they get larger.
Use germinating seed baits or digging and sieving to detect adults and nymphs prior to planting. Monitor crops after planting until establishment.
Control if more than 50 earwigs in 20 germinating seed baits or, control is indicated if one earwig is found in 20 spade samples.
Chemical control: Grain baits containing insecticide applied at sowing offer best protection. Insecticide seed dressings provide some protection. In-furrow sprays are not effective in protecting against dense populations. See Pest Genie or APVMA for current control options.
Cultural control: The black field earwig is mainly a pest in areas having heavy, black soils. Earwigs prefer cultivated soils rather than undisturbed soil (zero til). Use press wheels at sowing, which are set at 2-4 kg per cm width after planting rain, or 4-8 kg per cm in dry soil.
Widespread in Australia, Southern Europe, Asia, Africa and Hawaii.
- Crop Insects: The Ute Guide Northern Grain Belt
- Pests of Field Crops and Pastures: Identification and Control. Editor: P.T. Bailey