Pasture day moth

Agronomist, Damien Tanner (JSA Independent), has reported finding high numbers of pasture day moth caterpillars within a wheat crop at Nhill, in the Wimmera district of Victoria. The paddock has a high population of broadleaf weeds, including capeweed and volunteer canola. Damien says the caterpillars have not caused any feeding damage to the wheat crop, which is currently at the ear emergence stage. Pasture day moth caterpillars have a preference to feed on broadleaved weeds and generally leave cereals and grasses untouched where they have a choice.

Pasture day moth (Apina callisto) caterpillars are easily identified when they are fully grown by their dark brown to black colour and reddish-orange markings. They grow to about 50-60 mm long and have two prominent yellow spots near their rear end, which become more apparent as they mature in size. When viewed closely, they are noticeably hairy, with prominent bristles. The adult moths are brown with yellow markings on the wings and orange on the body. They fly in autumn and, as the name implies, are active during the day.

Pasture day moth caterpillars are often observed across the Victorian Wimmera in winter and early spring, but rarely cause issues for growers. They are also commonly found in southern New South Wales. In the past, pasture day moth caterpillars have caused damage in paddocks where caterpillars are present and broadleaf weeds are controlled with herbicide sprays. In these situations the grubs will transfer off the dying host plants and onto nearby crops. Damage has been reported on canola, cereals and pastures.

If pasture day moth caterpillars are present in crops, but only feeding on broadleaf weeds, there is usually little justification to spray unless these weeds are going to be removed by herbicides. If an insecticide spray is required, alpha-cypermethrin is reported to provide good control.