Cutworms can be difficult to identify: look for ‘fake legs’

There are two things for Alberta farmers to remember about cutworms, says Agriculture Canada entomologist Kevin Floate.

One is that Alberta Agriculture has an online cutworm reporting tool that farmers can use to enter data and see whether cutworms are a problem in a specific area. Find it by visiting www.agric.gov.ab.ca/app68/listings/cutworm/cutworm_map.jsp.

The other is that the Cutworm Pests of Crops on the Canadian Prairies field guide is available free online from Agriculture Canada to help farmers identify species and learn about the pests’ life cycles. It can be found at bit.ly 2zcNN43.

Floate told those at the Dec. 6 Farming Smarter conference in Lethbridge that different species of cutworm can be difficult to identify, even for entomologists. The field guide can help with that, but in Alberta the key species that damage crops are the redbacked, pale western and dingy species.

“Every year we have cutworm outbreaks caused by different species,” said Floate, but severity varies by region, weather and environmental conditions.

“These outbreaks affect all agricultural areas in the province. That’s the main message.”

Floate said most outbreaks occur in broadleafed crops planted after cereals, though broadleafs planted after broadleafs are the next most frequent crops affected.

Wireworms, white grubs, scarab beetles and even millipedes are often mistaken for cutworms, but all cutworms are alike in having soft bodies and three main body parts: head, thorax and abdomen.

Cutworms have three pairs of legs on the thorax and “fake legs” on the abdomen that disappear in later development. A full-grown cutworm is 2.5 to three centimetres long.

Different types of cutworm feed differently. Some feed on the surface, some in the crop canopy and some completely underground. Crop damage occurs when the worms are in the larval stage, Floate said.

Scouting should be done in the early morning or later evening when the worms are feeding.

Beneficial insects that attack cutworms can be encouraged by leaving hedgerows, wetlands and old homestead sites intact to serve as habitat.

Floate recommended spraying in specifically targeted areas rather than an entire field and to select a product with high specificity for the pest involved.

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