Both lygus bugs and diamondback moths can cause issues for canola growers, not only because of the damage they do to a crop, but also because they tend to show up later in the growing season, which can complicate or eliminate the option to spray.
For this episode of the Canola School, Jaden Wood-Sparrow, agronomy lead for G-Mac’s AgTeam, offers tips on identifying the best time to scout for these insects and what to do if you find you have significant populations in the field.
When scouting for lygus bugs, Wood-Sparrow says the plant is most susceptible to damage around the late flower to early podding stage. After that, since the lygus bug is a piercing and sucking insect, the pods tend to get too firm and the insect can’t penetrate the pod to suck the juices out.
“One of the best ways to tell if you’ve got a significant population is if you walk into that canola crop and you come out and you feel sticky. The lygus bugs, as they’re sucking those juices out, it kind of leaves a sap and and that gets on you when you’re walking through the crop,” explains Wood-Sparrow.
Another important factor to consider when scouting for lygus bugs the development of the bug as the younger ones aren’t doing the damage. You want to count the fourth and fifth instar and adult bugs, they will be the ones who could wreak havoc on your crop. In the video below, Wood-Sparrow goes through what specifically to look for and how many is too many when doing a sweep of your crop.
Diamondback moths pose a risk to canola crops as well and typically will show up as harvest nears.
“It’s kind of anytime after podding right up until close to harvest, we will generally see them move in a little closer to harvest because they they chew any green material. So when that canola plant still has big green leaves that the diamondbacks can chew on, they tend to do that before moving up to the pods,” says Wood-Sparrow.
With diamondbacks, you’re looking for chewing damage on the pods. You may see a little hole in the pod and when you break it open, all the seeds have been chewed out.
To combat either of these insects, Wood-Sparrow says there are a couple options. One of which for diamondbacks that is becoming more popular is Coragen, as the insect chews on the plant in order to be exposed to the insecticide, which then leaves beneficials otherwise unaffected.