Armyworm caterpillar warning for cereals

Armyworm caterpillars are on the march in the northern Wheatbelt and grain growers are advised to monitor crops carefully.

The Department of Agriculture and Food reports sightings near Nabawa, Geraldton, Mingenew and as far south as Dowerin.

Department research officer Svetlana Micic cautioned growers to check the threshold levels of armyworm caterpillars to ensure it was economically prudent to treat crops.

"Maturing barley crops are most susceptible. If they are still more than a week away from harvest, growers are advised to spray once they detect three large caterpillars or more per square metre," Ms Micic said. "Even if the crop is almost dry continue to check for armyworm, as they prefer the node under the head, which is the last part of the plant to dry.

Ms Micic said the threshold for wheat or oats was higher, as the armyworm caterpillars usually only ate the grains and the heads were not generally lopped.

"The spray threshold number for grubs in these crops is approximately 10 per square metre," she said.

Armyworm caterpillars are typically fat and smooth and distinguished by three parallel white stripes on the collar behind the head.

They can be detected in crops by their chewing damage to the flag leaf or by their green or straw coloured droppings about the size of a match head between crop rows.

For more information about armyworm caterpillars and treatment download the Armyworm in cereal crops Farmnote from the department's website agric.wa.gov.au