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Unidentified loopers

Agronomist, Olivia Wright (AGnVET Services), has reported issues with small caterpillars attacking an emerging canola crop. The paddock is situated northwest of Grenfell, in the Central West Slopes and Plains district of New South Wales. Olivia says the caterpillars were found chewing on cotyledons and new leaves, resulting in complete plant loss. About 20ha of the paddock has been completely eaten out.

The caterpillars are about 20 mm in length, but the exact species is unknown. They are not one of the common caterpillar pests known to feed on canola. They have been identified as a type of geometrid caterpillar, also known as looper caterpillars. The most common looper in New South Wales that feeds on canola is the brown pasture looper (Ciampa arietaria). Brown pasture loopers are dark brown to grey in colour with a yellow line along the body either side of a conspicuous dark band. They have red spots surrounding the breathing holes (spiracles) on the sides of the body. The loopers reported by Olivia have a pair of well-developed anal prolegs and a single pair of abdominal prolegs. They are dark brown in colour, with a darker band that runs along either side of their body.

Loopers usually cause crop damage when they transfer from summer and autumn weeds onto newly emerged seedlings. They are often problematic when crops are sown into old pasture paddocks, particularly those containing broadleaf weeds. Olivia says the affected paddock was a wheat crop in 2012. It is possible the caterpillars moved into the crop from neighbouring grass verges along paddock edges. A chemical spray was applied to the paddock to protect surviving canola seedlings from further attack. There are several insecticides registered to control loopers in canola.

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