Tell-tale features of a brown pasture looper

Brown pasture loopers are active this winter cropping season. When is enough enough? And can you tell the difference between this looper and other similar grubs?

Where have they been reported?

Recent foliar damage from brown pasture loopers (Ciampa arietaria) has been reported in canola in South West and North East Victoria. Minor damage has also been observed in canola near Lockhart in the NSW Riverina.

In late July, brown pasture looper damage was also seen affecting a lucerne stand near Kaniva, in the Victorian Wimmera. Similarly, 2-4 larvae per plant were observed in an old lucerne stand west of Elmore in Victoria’s Northern Country. In the same district west of Rochester, foliar damage had occurred in young lucerne undersown with oats.  

About brown pasture loopers

Brown pasture loopers are easy to identify once you know what to look out for. The distinctive feature is the two bright yellow wavy lines running down along the back. 

Wavy yellow lines running down the back of the brown pasture looper (Source: cesar).

 

Brown pasture loopers can be confused with pasture day moth (Apina calisto) or ‘herringbone caterpillars’ (Proteuxoa spp.). To further confirm identification of a suspected brown pasture looper, flip the grub onto its back or side and observe how many sets of abdominal prolegs it has. These are the leg-like appendages that caterpillars use to move. While most caterpillars have four sets of these, brown pasture loopers only have one set. They use their single pair of abdominal prolegs and one pair of anal prolegs to move using a series of back arches, which results in a characteristic looping motion.

Brown pasture looper has only one set of abdominal prolegs (top), whereas pasture day moth has four (bottom) (Source: cesar). 

 

Brown pasture loopers have only one generation per year. Adult moths emerge in autumn and remain active until about June. They typically lay eggs on plant leaves and stems in early to mid autumn. The caterpillars that hatch from the eggs grow to full size (20–35 mm) in about two months. Once larvae reach full size in early spring they pupate and remain dormant over summer. Brown pasture loopers are typically a problem for establishing crops, and become less concerning from late winter as they pupate and plants outgrow the caterpillars.

Our advice

Once caterpillars reach 30-35 mm in length, their damage potential is limited; they will soon pupate.

Control of brown pasture loopers can be assisted by natural enemies including parasitic wasps, which attack the eggs. They are also prey to spined predatory shield bugs and glossy shield bugs as young larvae. If chemical control is warranted, there are several insecticides registered against brown pasture loopers, however spot spaying or perimeter spraying is usually all that is required.

Click here for further information on brown pasture loopers, including lifecycle and management strategies.

 

Sources of field reports of brown pasture loopers

Ben Dumesny – Consultant, Premier Ag Consultancy Group (South West Victoria)

Chris Dunn – Agronomist, Landmark (Victorian Northern Country)

Bruce Larcombe – Agronomist, Larcombe Agronomy (Victorian Northern Country)

Simon Mock – Consultant, Clovercrest Consulting (Victorian Wimmera)