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Expanding weed control options in mustard

Eric Johnson is working to develop new weed control options for mustard, including B. carinata.
Photo courtesy of  Eric Johnson, AAFC.

Remember the old days of weed control in canola before herbicide-tolerant hybrids came along? Think Westar canola and herbicides like Treflan, Edge, Muster and Poast. For mustard growers, that is today’s reality, but through work done by weed scientist Eric Johnson at Agriculture and Agri-Food Canada (AAFC) at Scott, Sask., under the Pest Management Regulatory Agency’s (PMRA) minor use program, the choices may be slowly expanding for mustard growers.  

The research is being funded by AAFC’s Growing Forward 1 and 2 programs, the Western Grain Research Foundation, Saskatchewan Agriculture Development Fund, Mustard 21 Canada Inc., Agrisoma Biosciences Inc., and the Saskatchewan Mustard Development Commission. The goal is to expand the weed control options for mustard growers, whether they grow yellow (Sinapis alba), oriental and brown (Brassica juncea) or Ethiopian (Brassica carinata) mustard.

“There are a few things that mustard growers need to know, and [one of them] is not all herbicides registered on mustards can be used on all mustard types,” says Johnson. Part of his research is looking at expanding some of the registered herbicide and crop options.

Johnson says trifluralin can be used on all mustards including B. carinata, while Edge is only registered on S. alba. He explains that Edge can cause injury in brown or oriental mustards. PMRA has completed its re-review of Edge, opening the door for new crops to be registered. Johnson is looking at Edge on B. carinata with some promising results.

Assure II (quizalofop) and Muster Toss-N-Go are registered on B. juncea and B. carinata. However, the Assure/Muster tank-mix is only registered on B. juncea and Johnson cautions that there are some concerns with this tank-mix on B. carinata, which they are trying to sort out. The Muster label states application stage from the four leaf but prior to bolting, and Johnson says that needs to be followed fairly carefully.

“We have seen some crop injury in B. carinata with the Assure Muster tank-mix. We’ve been looking at herbicide rates in the tank-mix along with adjuvants and at various leaf staging. You’ll need to follow the label fairly carefully as we’ve seen significant injury if you apply too early, especially with Muster,” says Johnson, who adds they are continuing to try to sort out the best application parameters.

Johnson is also investigating Authority herbicide. Authority is registered on chickpea, field pea, flax and sunflower as a pre-plant or pre-emerge application for control of kochia, lamb’s quarters, redroot pigweed and wild buckwheat. He is looking at its use in B. carinata, B. juncea and S. alba. Registration has been submitted only at the low rate of 43 acre per jug.

“We have seen some crop injury from Authority if there is heavy rainfall in May. It is something the crop seems to be able to get through but the risk is there. It isn’t perfect tolerance to the herbicide,” cautions Johnson. “If this does become registered, I would suggest growers try it on limited acres until they get a better handle on how it performs on their land.”

Non-GMO herbicide tolerance development
Another weed control initiative that Johnson is working on is the development of herbicide-tolerant mustards. This program is using non-GMO techniques using chemical mutagenesis or gamma radiation to try to get Group 2 and 4 tolerances into mustards.

“We are going the non-GMO route because the European Union market is very important to mustard exports, and a GMO mustard would likely be a non-starter there,” says Johnson.

The goal of the program is to develop B. carinata and B. juncea varieties with Group 2 imidazolinones and sulfonylureas tolerance and Group 4 tolerance. In S. alba, they are looking for Group 2 imidazolinones and sulfonylureas tolerance along with Group 4 tolerance to dicamba. Johnson is screening the germplasm for tolerance. The research is still in early stages.

While growers wait, weed control challenges remain, especially with wild mustard control.  Johnson says if Authority is registered, it will help with other weed problems like kochia, but good wild mustard control remains an issue – and in S. alba, there are no options for wild mustard control at all.

Still, Johnson says growers do not need to strive to achieve the same weed control performance in mustards as they achieve with Liberty Link or Roundup Ready canola. Johnson and researcher Hugh Beckie with AAFC at Saskatoon, Sask., looked at the competitiveness of mustards in comparison to hybrid canola. He says mustard grows faster and is much more competitive than hybrid canola. Yellow mustard was best able to suppress weed growth, followed in decreasing order of weed competitiveness by oriental mustard and hybrid canola, open-pollinated canola, and canola-quality mustard.

“When growers ask for weed control options as good as herbicide-tolerant canola, I suggest to them that shouldn’t be the goal. Mustard is extremely competitive and doesn’t suffer the same yield loss as canola under weed competition. If you are able to set the weeds back in mustard, the crop does a good job of suppressing the weeds further and you won’t suffer the same yield loss,” says Johnson.

 


June 2, 2014
By Bruce Barker

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