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Pasture webworm

Agronomist, Ben Batters (Elders), has reported pasture webworm (Hednota spp.) causing damage to a wheat crop south of St. Arnaud, in the Wimmera district of New South Wales. The damage is quite patchy, with at least 20% of the paddock affected. The paddock was pasture in 2009 and has sandy-loam soil. Ben says the pasture webworm caterpillars could be observed, along with their tunnels near the base of plants.

Pasture webworm may attack establishing crops of wheat, barley and rye. Larvae are usually light-dark brown in colour, growing to about 18 mm long. They have a smooth body and shiny dark heads. Pasture webworm feed at night and hide inside web-lined tunnels beneath the ground by day. They typically feed on the soil surface or pull plant material into their tunnels. The adults are long-legged moths with enlarged mouthparts arranged in a beak-like projection. They are 10-12 mm long with a wingspan of about 22 mm.

Careful digging at the base of recently damaged plants may reveal web-lined tunnels with caterpillars inside, or searching at night may reveal feeding activity. When monitoring, look for leaves protruding from tunnels in the soil. Crops sown into paddocks where fine, dry grasses were prevalent during autumn are most at risk. Click here for images of the pasture webworm.

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