SASKATOON – Sulfentrazone, a herbicide with a new mode of action for Western Canada, has been undergoing tests under the minor-use herbicide registration process at Agriculture Canada’s research centre in Scott, Sask.
Eric Johnson, an Agriculture Canada researcher at Scott, told farmers at the Pulse Crop Days held as part of crop production week in Saskatoon that sulfentrazone is a group 14 and few group 14s are available in Western Canada.
“So it’s an important tool in resistance management,” said Johnson.
The trade name in the United States is Spartan.
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“It’s not going to be registered in Canada as Spartan. DuPont already has that name in Eastern Canada and that’s for tribenuron or Express. I don’t want people going to Eastern Canada and buying Spartan to spray on their chickpeas, then killing them,” he said.
Sulfentrazone is registered on soybeans, tobacco and sunflower in the U.S.
“They also have a section 18 registration, which is like a minor-use registration, in North Dakota. That’s to control wild buckwheat in chickpea and dry pea. More recently they have a section 18 for control of kochia in flax,” he said.
The herbicide affects the cell membranes in susceptible plants. Johnson said symptoms include leakage of water and solutes out of the cells and water soaked area on the plant before the plant finally dies.
“We’ve screened it for tolerance in chickpeas, lentils, dry beans, lupins and faba beans, plus crops like sunflower, flax and alfalfa seed,” said Johnson.
“For pulse crops, chickpea is most tolerant, faba beans are very tolerant, then field peas are OK, but there will be injury at higher rates. Lupins are about equal to field pea, while pinto beans are marginal and lentils are very sensitive.”
Sulfentrazone provides excellent control of wild buckwheat and good control of kochia.
“When it works, it’s one of the best kochia killers I’ve ever worked with. It will also control group two resistant kochia,” said Johnson.
“It’s effective on lamb’s quarters and redroot pigweed, but it’s very weak on wild mustard and stinkweed. We’re looking if we can selectively control kochia in tame mustard with this product. But it does do a pretty good job on shepherd’s purse, even though it’s in the mustard family. So not all mustard species have some resistance to it.”
With its weed control spectrum, Johnson feels it’s more of a southern to middle prairies type of product. It’s not as good for the weeds found in areas like northern Alberta.
“When we started this, the rate for control was 280 grams active ingredient per hectare, (114 grams per acre) based on soybean rates in the United States. I think that rate is too high for the weed control we get at lower rates. Plus this is a residual herbicide, we have recropping concerns and that rate will cause recropping issues,” he said.
Because of the recropping issues, Johnson thinks the final rate might be around 57 grams per acre, but research at Scott has tested down to seven grams per acre.
“We’ve found that on certain soils we can go to lower rates. On high organic matter soils, this product might not work all that well. We might get into a situation where we’re looking at rates in the 100 gram area, (40 grams per acre) much lower than we first thought we’d be using.”
Johnson said he’s seen injury to lentils three years after application and most chickpea growers are going to be lentil growers. Carryover is one of his main concerns, but he thinks he can solve that through rates.
“While soil pH may play some role in this carryover, soil cation exchange capacity – organic matter and clay content – will have more of an impact. If you’ve got a low organic matter, low clay content and a sandy soil, there might be a fair amount of carryover,” he said.
“Barley is the most tolerant to carryover the following year. Spring wheat and durum were more susceptible to carryover injury, while canaryseed was quite sensitive. Even if we get the rates low enough, I’m pretty sure you won’t be able to grow canaryseed the year following sulfentrazone application.”
Because sulfentrazone is a soil applied herbicide, Johnson said there are issues of consistency.
“When we first started working with it, we almost gave up on it because there were some dry springs when it didn’t work very well. We did some things to try to improve consistency – fall application, using the snow melt to wash the herbicide into the rooting zone, but that didn’t improve the control. We found we had to go to a higher rate if using it in the fall,” said Johnson.
“Incorporation can help, but if you’re going to have failures it doesn’t help that much. Most of the work we’ve done is without incorporation. We’ve typically applied it in pulses after seeding but before crop emergence. We tank mix it with glyphosate and it can be used in the burn-off application.”
Isoxaflutole, another herbicide in Johnson’s minor-use program, is now marketed by Bayer CropScience.
“It’s a corn herbicide with a unique mode of action. Chickpeas is the only crop that tolerates it – it will kill any other pulse crop,” said Johnson.
“We’ve worked with this a little bit. It controls wild mustard very well. We’ve been looking at combining sulfentrazone with it at low rates. It’s also soil active so there are some recropping issues. We have found we can get very good broad spectrum weed control with reduced rates of both products, such as a half rate of isoxaflutole and a quarter rate of sulfentrazone.”
While Johnson said both products have promise for chickpea growers, he still has work to do.
“We need to get the rate structure sorted out for soil types and more recropping work. And we need an intensive extension program to growers, so they’re aware of the expectations.”
He said NuFarm has signed a marketing agreement with FMC Corp. to market sulfentrazone in Canada. It may be possible for a 2007 registration, but it’s highly unlikely that there will be product available in 2007.
“For isoxaflutole, Bayer is monitoring our research. They’ve made no commitment yet, but they may support it in the future.”
