Lentils are one of those crops that can be difficult to keep free of weeds. Lentils are a poor competitor with weeds not just as seedlings, but throughout the growing season, as well.

Over the past five years, the Western Applied Research Corporation (WARC), has been doing research trials that look at herbicide layering to control weeds in lentils, with some strong evidence for efficacy.

The research group carried out the same treatments at Saskatoon, Birsay, Swift Current, Redvers, and Scott, Sask. The five locations used gave a wide range of growing conditions and of course, encompass different soil textures and zones — not enough moisture wouldn’t activate soil-applied herbicides and it’s important to give an accurate representation of conditions across the province.

In this Pulse School episode, Jessica Enns, general manager at WARC, joined Kara Oosterhuis to talk about trial results and how applying something with residual activity will help farmers reduce their chances of herbicide resistant weeds.

“What we wanted to focus on is some of the pre-seed residual options that farmers use,” says Enns. “Mainly we tried to focus on the Group 14 and Group 15s.”

In the video below, Enns discusses how flumioxazin (Group 14), pyroxasulfone (Group 15), carfentrazone (Group 15), and their combinations performed to control weeds such as kochia, wild mustard, or volunteer canola:

Looking at other modes of action is so important because the rise of Group 2 resistant herbicides are really putting a damper on weed control and decreasing yield. In Enns’ words “they’re just not cutting it anymore.”

Herbicide layering isn’t a new technique but Enns thinks that perhaps farmers need to be reminded of its efficacy.

“Producers maybe just need a little bit of  a nudge to kind of utilize it. It is more of an expensive cost than just going in with an in-crop herbicide, but I don’t think they understand how effective it is,” says Enns.

Enns says that they were expecting to see residual herbicides do better than just glyphosate, and they did, which isn’t much of a surprise.

“One thing I was happy to see was that the Goldwing with glyphosate did quite well, and that one was quite consistent,” says Enns, adding that it’s a product that doesn’t typically get used often, and in combination with residual products, was effective.

Another outcome of the trials was that in 10 herbicide combinations, any lentil fields with residual herbicides on them were most effective at maintaining yields, and the lowest yields were found in fields with just an in-crop application of Solo, an application of spring-applied glyphosate or glyphosate plus saflufenacil or Goldwing.

“It really kind of came down to the fact that anything that didn’t have a residual component tended to yield quite poorly, versus all the fields that had a residual did quite well,” says Enns.

All in all, the research used 16 different herbicide combinations, but no matter what they used, any herbicide combination was better than just glyphosate alone. Enns adds to rotate modes of action, and keep an eye out for herbicide resistant weeds.

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