Pasture day moth

Agronomist, Neil Durning (AGnVET Services), has recently found grubs of the pasture day moth in a paddock at Junee, in the southwest slopes of NSW. They are reported to be causing some biting/chewing damage to oats, although the damage at this stage is not severe. They have also been found in lucerne-pasture paddocks.

Pasture day moth (Apina callisto) caterpillars are easily identified when they are fully grown (about 50-60mm long) by their dark brown to black colour and reddish-orange markings. They also 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. Pasture day moths are found in most southern areas of Australia, ranging from lower Queensland to Tasmania.

Neil says the grubs are fairly widespread across the affected paddocks, with between 2-4 grubs observed per 10 square metres. The grubs are about 50mm long and mainly seen feeding on the tips of plants. The typical ‘window pane’ effect can be seen on some plants where the upper green leaf surface has been removed to leave a clear or white patch. Most damage is likely to occur on the weeds, particularly capeweed, which Neil says are fairly common within the paddocks.

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. Eggs are laid in pasture and hatch at the onset of rains. When the larvae are fully grown they may be seen burrowing in the soil before becoming pupae. The pasture day moth passes through only one generation per year.

Pasture day moth caterpillars have a preference to feed on broadleaved weeds and will often leave cereals and grasses untouched where they have a choice in pastures. However, in paddocks where caterpillars are present and broad-leafed weeds are dead or dying from a previous herbicide spray, the grubs will transfer off the dying host plants and onto cereal plants. It is important to correctly identify caterpillars as an assortment of species may be present including brown pasture looper and pasture web worm.