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Pest watch: scouting for cereal leaf beetles

Pest watch: scouting for cereal leaf beetles

Larvae damage could begin as early as this month

By Kaitlynn Anderson
Staff Writer

Growers and crop scouts across the province may want to be on the lookout for cereal leaf beetles in their fields.

While adult beetles have already appeared in many fields, the larvae will be the real issue, Tracey Baute, a field crop entomologist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), said in an article on Thursday.

These young pests could hatch from eggs at anytime now.

As daily growing degree days have accumulated at a fast pace, “the populations and feeding activity could catch us off guard,” Baute said.

Since initial larvae feeding can be difficult to notice, farmers should carefully watch their crops.

“We are likely another week before the larvae and damage could be visible,” Baute told today.

While larvae tend to cause the most damage in June, they can begin feeding as early as May, she said in the article.

Both young and adult versions of this pest feed on plant tissue between leaf veins in cereal crops, she said. This skeletonizing effect may cause fields to have a silver look.

To help growers find and identify these pests, Baute offered some scouting tips in her post.

When searching for cereal leaf beetles in their fields, producers should examine 20 plants in five different areas of each field, she said.

Since these pests can cause increasing amounts of damage in a matter of days, farmers may want to walk their fields every five days, she added.

Producers may want to be aware of threshold levels to ensure they only use foliar insecticides when necessary.

  • Before boot stage: producers may want to spray if they find “an average of three larvae per tiller,” Baute said.
  • After boot stage but before heading: growers may want to execute a control method if they find one cereal leaf beetle adult or larvae per stem.
  • Early heading stages: producers may want to spray their fields if the pests feed heavily on the flag leaves.

Once they reach the flag leaf stage, crops are more susceptible to damage, Baute told Many fields in southwestern Ontario are currently approaching this point.

Scouts can identify adult beetles by their metallic blue-green wings, and reddish-orange heads and legs, Baute said in her article. Due to an outer coating made of fecal material, the larvae initially have a black colour. However, underneath this outer coating, they are a yellowish colour.

For more information on cereal leaf beetles, check out the Field Guide.


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