Pasture tunnel moth

Summary Top

Pasture tunnel moths are endemic to Australia. Their larvae are grass-feeders and are a sporadic pest of pastures and some cereal crops in higher rainfall areas of Australia. The larvae construct vertical, silk-lined tunnels that protrude above the soil surface forming ‘chimneys’. They use these tunnels to hide during the day, emerging at night to feed nearby on crop or pasture plants.

Occurrence Top

Pasture tunnel moths are native to Australia and have been recorded in all eastern states of Australia, including Queensland (Darling Downs), New South Wales, Victoria, South Australia and Tasmania. They are generally a pest in higher rainfall areas, and are restricted to pastures/crops in areas with greater than 500 mm annual rainfall.

Pasture tunnel moths are mostly found in pastures/crops with greater than 500 mm annual rainfall

Description Top

Pasture tunnel moth larvae have a slender (approximately 2-3 mm wide – about as thick as a match), grey-brown coloured body with a dull, matt almost translucent surface that makes them very inconspicuous in the soil. The head is black and shiny, contrasting with the rest of the body. Each abdominal segment has several rounded, shiny lumps each bearing a long hair; there are two pairs on top and a single one on each side. They grow from 25- 30 mm in length and have several long sparse setae (stout hairs) around the head.  

Adult moths are elongate, white-cream in colour and glisten like satin. They are around 20 mm long and have a wingspan of approximately 25 mm. The abdomen tapers to a slender ovipositor and is longer than the folded wings.

Lifecycle Top

Adults emerge from their pupation sites from late November through to January, with the time of emergence being influenced by rainfall; large emergences follow heavy rains. The moths remain among grasses during the daytime, and at sunset they are attracted to tall objects such as posts or tree trunks, where mating occurs. Egg-laying takes place late summer and early autumn.

The larvae cease feeding in October and then close the entrances to their tunnels.

Behaviour Top

Pasture tunnel moth larvae construct vertical, silk-lined tunnels about 70 mm deep that protrude above the soil surface forming ‘chimneys’ of about 8 mm in a collar of silk and grass fragments. They use these tunnels to hide during the day, emerging at night to feed nearby on crop or pasture plants. Often, rain stimulates pasture tunnel moth larvae to come to the surface and feed, however, heavy rains can wash away, or collapse, the tunnels.

Populations of pasture tunnel moth larvae are favoured by shorter, more open pastures and possibly by the drier, more freely draining soils.

Pasture tunnel moth larvae build vertical, silk-lined tunnels that protrude above the soil surface forming ‘chimneys’.

Similar to Top

Pasture webworm in that the older larvae also live in web-lined tunnels beneath the ground, but pasture tunnel moth larvae can be distinguished from pasture webworm by their slender size and the absence of webbing on leaves. Pasture tunnel moth tunnels are silk lined, and have an aboveground ‘chimney’, whereas pasture webworm tunnels have only an opening at ground level. Blackheaded pasture cockchafer larvae also live in underground tunnels but are the typical C-shaped scarab larvae tunnels.

Crops attacked Top

Pasture tunnel moth can cause significant damage to annual and perennial grasses, and occasionally clovers. They have also been recorded damaging cereals (wheat, and barley) and canola crops, especially following a pasture phase.

Damage Top

Pasture tunnel moth caterpillars are generally considered a minor pest; most damage by this pest occurs from July to September. They feed at night near their burrows, often tearing leaves and dragging them back into their tunnels. Chewed-off leaves can often be found strewn on the ground where pasture tunnel moth caterpillars have fed.

When the insects occur in high densities, patches of establishing cereal crops or pastures may be completely defoliated. Damage is usually not noticed until early winter, with the worst period being from July until September. Damage is often not observed in lush pastures because only a thinning of the sward occurs. Infestations of greater than one hectare are rare.

The timing of pasture tunnel moth appearance in paddocks often coincides with the appearance of blackheaded pasture cockchafer.

Rain often stimulates pasture tunnel moth larvae to come to the surface to feed

Monitor Top

Inspect paddocks for signs of damage and formation of chimneys or silk-lined burrows in mid-winter.

Economic thresholds Top

There are no economic thresholds established for this pest, however, densities of over 70/m² appear to be damaging.

Management options Top

Acknowledgements Top

This article was compiled at cesar by Alana Govender and Garry McDonald (cesar).

References/Further Reading Top

Bailey PT. 2007. Pests of Field Crops and Pastures. CSIRO Publishing, Melbourne, Australia.

Common, IFB. 1990. Moths of Australia. Melbourne University Press 665 pp.

Common, IFB.  1994 Oecophorine Genera of Australia I: The Wingia Group (Lepidoptera: Oecophoridae).  Monographs on Australian Lepidoptera Series 3. CSIRO Publishing 300 pp.

Herbison-Evans D and Crossley S. Philobota productella (Walker 1864); Pasture Tunnel Moth. Coffs Harbour Butterfly House. Available at < http://lepidoptera.butterflyhouse.com.au/oeco/product.html> (accessed 11^th Jan 2015).

Roberts RJ, Schroder P, Davies HI and Porter MR. 1982. Philobota (Lepidoptera: Qecophoridae) abundance in relation to different periods of withholding superhosphate application to pastures. Proceedings of the 3rd Australasian Conference on Grassland Invertebrate Ecology.  K.E. Lee (Editor).