Pest caterpillars in autumn

Autumn rains have triggered the emergence of several species of pest caterpillars

Where have they been reported?

Armyworms: Surprisingly large numbers of armyworm pupae and a few recently emerged moths (Persectania ewingii) were found in the Wycheproof area of the Victorian Wimmera, under or around a cereal stubble in a paddock destined for lentils. Whilst this may be concerning for the grower, they are unlikely to become a problem in the subsequent lentil crop.

Anthelids: Large collections of anthelid moths, the adult form of the distinctive ‘woolly bear’ caterpillars, were seen around buildings in the Swan Hill area of the Victorian Wimmera immediately after breaking rains. The moth was identified as Anthela euryphrica.

Pasture tunnel moth: In the high rainfall areas of southwest Victoria, pasture tunnel moth (Philobota productella) larvae have been reported damaging pasture from Hamilton to Warrnambool. The larvae were, as is often the case, found alongside cockchafer larvae.  

Cabbage white butterfly: An irrigated trial crop of winter canola near Birchip in the Victorian Mallee, at the 6-8 leaf stage, has been moderately damaged by the distinctive, uniformly green, larvae of the cabbage white butterfly (Pieris rapae). They have also been seen in spring-sown canola near Werneth in the southwest of Victoria. 

Armyworm pupae and moths observed in cereal stubble (Source: Roy Daykin)

 

Left: Anthelid moths with distinctive wing markings and ornate antennae (Source: Craig Muir). Right: Woolly bear caterpillar often found in winter pastures and some cereals (Source: SARDI) 

 

About these pests

Armyworms: The armyworm pupae found in the Victorian Wimmera were emerging from the previous spring generation in cereals (in the 2015 season, armyworms infestations were widespread and damaging). Armyworm moths are mostly obligate migrants and will fly some distance before mating and egg-laying. Eggs are generally laid within standing stubbles or dried grasses.

For further information on armyworms, including their occurrence, lifecycle, behaviour, damage symptoms and management strategies, visit our PestNote series.

Anthelids: There are many species of anthelids; the moths are often characterised by distinctive wing patterns and large ornate antennae. Most anthelids have a single annual generation that commences with the autumn rains. The caterpillars characteristically have tufts of stout hairs or bristles covering their body. The caterpillars feed on grasses and sometimes cereals but not on other crops; their numbers usually build up in pastures or roadside vegetation. They become more obvious in late winter and early spring where they can move into and damage the edges of crops.

For further information on grass anthelids, including their occurrence, lifecycle, behaviour, damage symptoms and management strategies, visit our PestNote series.

Pasture tunnel moth: A pest of pastures and some cereals in higher rainfall areas of Australia, the slender 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. 

Cabbage white butterfly: These are the common white (with small black spots) butterflies that can be seen during the day in early autumn visiting brassica plants in broadacre situations and in home gardens. Eggs are laid on brassica leaves (including spring-sown and winter canola), and the emerging caterpillars chew holes in the leaves and along leaf margins. The cabbage white butterfly is a warm season pest and moths disappear as the cool sets in. Larvae will persist over winter, causing minimal damage to plants, and pupate in spring. They tend not to be a major pest of canola through winter, but can defoliate spring-sown canola.

Our advice

Armyworm moth egg-laying will produce a generation of caterpillars that may potentially begin defoliating cereals in early-to-mid winter. Although it would be unusual to have two successive years of damaging armyworm infestations, monitor crops, particularly those that are sown into standing stubbles.

Anthelid caterpillars will principally appear in grass pastures, and less commonly in cereals. Monitor for possible crop invasion in late winter, although control is rarely warranted.

There are few options to control pasture tunnel moth in established pastures. There are no chemicals registered for this species, although field reports suggest similar products (and rates) used against blackheaded pasture cockchafers may provide satisfactory control. Because the caterpillars are active at night, application of chemical is most effective if it is applied late in the afternoon or evening, to maximise contact.

Cabbage white butterfly larvae are unlikely to cause problems in autumn-sown canola, as moths will soon disappear. In spring-sown canola, crops can withstand surprising levels of defoliation before sprays are justified.

 

Sources of field reports of these pests

Kelly Angel – Agronomist, Birchip Cropping Group, Birchip (Victorian Mallee)

Roy Daykin – Agronomist, Elders, Wycheproof (Victorian Wimmera)

Cameron Morris – Agronomist, Landmark, Hamilton (South West Victoria)

Craig Muir – Agronomy Consultant, AGRIVision, Swan Hill (Victorian Mallee)

Tim Pilkington – Agronomist, Compass Agribusiness, Ballarat (Victorian Central District)