Canola School: Aggressive lygus bugs and their enemies


Lygus bugs attack several broadleaf crops, including alfalfa, flax, faba beans, lentils, and canola.

They are a pest of concern that have been a focus for Hector Carcamo, research scientist at Agriculture and Agri-Food Canada, Lethbridge, Alta. He joins Kara Oosterhuis for this Canola School episode to talk about lygus bug species, the conditions they thrive in, and what makes them tricky to research.

“Lygus bugs are a very interesting pest, they happen to be a native species, so lygus bugs have been here before, feeding on various plants, and when we started doing agriculture, they found that some of our crops are very attractive to them,” says Carcamo.

Especially this year, with dry environmental conditions, there have been outbreaks of the pest from coast to coast, says Carcamo.

Lygus bugs overwinter as adults in shelterbelts or field edges. They start flying and feeding on whatever plants they find in the spring. When those plants are done, lygus will move on to other crops.

Lygus populations seem to be more synchronized with canola crops this year, especially since the crop is stressed due to hot and dry conditions. Canola is damaged by lygus bugs around flowering, causing aborted flowers and pods, and even visible gaps in the flower raceme of the plant, which is very aggressive.

Carcamo says that when thinking of thresholds for lygus bugs, it’s important to remember the crop stage — for example, two to three lygus bugs per sweep at the end of flowering.

“How do you know that the lygus are causing damage at the time? You can actually visually confirm that by walking through the field, and if you’re coming out with your pants full of sticky stuff, when the crop is oozing from the pods, that will be an indication that the lygus bugs are causing damage. You’re going to see that in the middle of the day, when you have a very hot day,” says Carcamo.

It might be too late to do anything about lygus bugs now, if they’re already doing damage, but Carcamo says that lygus bugs are very unpredictable — it’s possible that there would be large populations next year, unless there’s a cold winter, or a very wet spring.

There are many natural enemies that will eat lygus bugs, including a parasitic wasp, spiders, and even larger lygus bugs will eat smaller ones.

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Canola School (view all)Season 13 (2021) Episode 8

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