Pulse School: Taking a closer look at pea leaf weevil pressure

The pea leaf weevil might be a difficult tongue twister of an insect name to be said 10 times fast, but this pest can be even more difficult to control in your peas and faba beans. Across the Prairies, their tell-tale notching is rearing its appearance.

In this episode of RealAgriculture’s Pulse School, prairie field editor, Kara Oosterhuis speaks with Nevin Rosaasen, of the Alberta Pulse Growers, at canolaPALOOZA at Lacombe, Alta. The pair discuss the recent pressure that has been scouted, especially since most are past that 20-30 day mark of seed treatment efficacy, and the life-cycle of the insect is around two weeks.

“The adult female will ovi-posit an egg at the base of the pulse plant of peas and faba beans. That egg, when it hatches, those larvae (will) begin their journey down to find the nodules. It’s the feeding on the nodules that’s the actual yield reducing component of this insect pest,” Rosaasen explains. “The above ground feeding is just an indication that yes, there are adults there.”

When it comes to scouting anything in your pulse crops, Rosaasen says “If you don’t have a shovel — you’re doing it wrong.” You always have to dig up plants and look at the roots.” (Story continues below player

“So the best way is to first look along the leaf margin for pea leaf weevil, to see if they’ve been notching at the edge of the leaf. It’s very easy to spot — it looks as though your grandmother has taken pinking shears along that leaf margin, so it is very easy to identify,” he explains.

“After that, start digging up plants, knock the dirt off if you can, and you might be able to find a larvae that’s eating inside the nodules.”

Rosaasen notes although producers may become panicked when they see the feeding on their plants, more often than not, spraying is not recommended.

“Once you have adults there, they have already ova-posited that egg, and a non-selective insecticide is not going to control those larvae above ground. When you do go in and use a spray you are actually reducing all the beneficial insects, parasitoids, and predators in the field. So we don’t recommend spraying for pea leaf weevil.”

According to Rosaasen, there are mapping tools currently in the works, that will give producers an extra hand in knowing their area.

“They absolutely enjoy weather around that 20 degrees Celsius — that’s when they can fly. We do have researchers tracking their flight and how far they can fly,” he says adding they have determined the flight path by putting a pea leaf weevil on the end of a string, and letting it fly.

“So they are mobile, they do move, and they are an insect of concern here in Alberta.”

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