Weevils, grasshoppers on Prairie farmers’ radar

As this year’s crops develop on the Prairies, several pests are growing right along with them. Cabbage seedpod weevils, grasshoppers and alfalfa weevils are all on farmers’ radar right now — and wheat midge may be, soon.

Here’s a look at the insect situation across the Prairies:

Cabbage seedpod weevils are popping up in Alberta and Saskatchewan. During a recent Twitter chat, Brandon Gibb wrote that spraying was going “full tilt” for cabbage seedpod weevil on his farm near Hill Spring, Alta., about 100 km southwest of Lethbridge.

Gibb reported counts as high as 10 weevils per sweep in some fields. The economic threshold is about 20 weevils in 10 sweeps, according to the Canola Council of Canada.

Shelley Barkley, insect research technologist for Alberta Agriculture and Rural Development (AARD), reported farmers were spraying for cabbage seedpod weevil in southern Alberta and surveying for the pest in central Alberta. AARD is mapping survey results online.

Cabbage seedpod weevil has traditionally been a southern Alberta pest — but Grant McLean, crop management specialist with Saskatchewan Agriculture in Moose Jaw, said he’s hearing from producers and consultants that counts are high in southwestern Saskatchewan. The weevils have moved as far east as Gravelbourg and Moose Jaw, he added.

McLean said the weevils have reached economic thresholds, and farmers are spraying canola and brown and oriental mustard crops. Yellow mustard tolerates the pest.

The weevils start laying eggs in canola when pods are three-quarters to one inch long. AARD entomologist Scott Meers wrote that for best results, people should spray before pods are one inch long, “but with high numbers (it) would still be worth spraying later.”

The Canola Council of Canada recommends spraying for cabbage seedpod weevils when crops are in 10 to 20 per cent flower, which is when 70 per cent of the plants have three to 10 open flowers.

Alfalfa weevils have been confined to the southeast and east central regions of Saskatchewan the last couple years, said McLean. But the pest is now moving as far west as Gravelbourg, Moose Jaw, and even a little farther.

“We’ve seen fairly significant damage,” said McLean. Alfalfa weevils are currently in the fourth instar in Saskatchewan, he adds.

The latest Manitoba insect and disease update also reported alfalfa weevil damage in eastern Manitoba and the Interlake region.

Farmers with alfalfa weevil infestations can either cut alfalfa to reduce losses or apply insecticide. “But with the weather we’ve been having, guys have been cutting hay like crazy,” said McLean.

If the alfalfa regrows quickly, the larvae may survive, according to Manitoba Agriculture Food and Rural Initiatives (MAFRI). Farmers should also take into account the life stage of the larvae before spraying.

Some grasshoppers in all provinces

McLean has heard of grasshoppers in the warm, sandy soils in southwest and west-central Saskatchewan, and producers should be scouting.

“We haven’t seen significant populations for a while, with the wet conditions we’ve been experiencing. But certainly I think there are going to be local hotspots that individuals may be seeing later,” said McLean.

McLean said the majority of the grasshopper hatch should be complete now. Hoppers don’t cause much damage until they get to the third instar stage, he adds.

Grasshopper counts are high in many parts of Manitoba, and some farmers are spraying, particularly on field edges. Hoppers are easier to control in early stages, which is where they’re at now, according to MAFRI. The hatch is also nearly complete in Manitoba.

Meers wrote that so far most of Alberta’s grasshopper pressure seems to be in the Peace region.

Wheat midge season begins

MAFRI’s insect and disease update predicts wheat midge will start emerging in Manitoba in the first week of July.

Alberta is just entering the wheat midge season. Ashley Glover, Parrish and Heimbecker’s agronomist for southern Alberta, reported wheat midges are starting to fly in her region.

Wheat is susceptible to the midge from the time the head is visible to anthesis, Meers wrote.

“Remember that wheat in the flag leaf often shows the head through the side of the boot — midge can lay eggs on there,” Meers added.

Farmers, agronomists and others can discuss insect issues on Twitter through #abbugchat. Manitoba producers can also submit agronomic questions to CropChatter.ca.

— Lisa Guenther is a field editor for Grainews at Livelong, Sask. Follow her @LtoG on Twitter.

About the author


Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



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