Miss pre-seed burn off? What are the options now?

Kochia is a difficult weed to control in many crops. The rise of Group 2 resistance in the weed has resulted in few herbicide choices for producers.  |  Michael Raine photo

Cool spring weather meant many growers couldn’t wait for a nice flush of weeds before laying down a pre-seed burn down for their pulse crops, which means timing their in-crop applications is even more critical than usual this year.

“We’re hearing that a few fellows are stuck where their crop is coming up and they didn’t get the burn off done,” said Clark Brenzil, provincial weed specialist at Saskatchewan Agriculture.

He said growers in this situation shouldn’t try to push the burn-down window too close to crop emergence, which happens quickly in warm weather.

“Any plant that is up will get killed,” Brenzil said.

“If you move that window much past that point where you start to see the little cracks coming out of the ground, you will see lots of injury and you will lose lots of the crop plants.”

The best way to address missing the burn down is to try to get in with your post-emergent application as early as you can to take care of those weeds that were there before the crop came up.

This is because weeds that are present before the crop emerges are many times more competitive against the crop than weeds that come up after a herbicide treatment is done early on in the crop-emergence period.

“It might not be pretty, but as far as paying the bills go, the early application is where it’s at this year for sure,” Brenzil said.

Sherrilyn Phelps, agronomy manager at Saskatchewan Pulse Growers, said cool conditions have weeds and crops emerging at the same time in the province.

“For pulses, the critical weed-free periods are fairly early in the season, so managing weeds earlier vs later is going to be key,” Phelps said.

“Based on a lot of issues with weed control from 2019 due to dry conditions early on and the crop being too advanced by the time the weeds actually emerged, growers can expect strong weed pressure.”

Brenzil said the moist fall last year in many parts of Saskatchewan may mean cleavers will be tough to control this year.

“They’re probably going to see cleavers becoming more of a problem, and given the predominance of Group 2 resistance in cleavers that could be a bit of a challenge because Group 2s are the real workhorse of the herbicide world in pulse crops,” Brenzil said.

Wet conditions last fall delayed harvest and many growers were unable to get to fall herbicide applications, which means winter annuals and perennials will be a challenge especially if they were not managed with a burn down this spring.

“They will be sitting there ready to go as soon as the condition starts to improve. So we have dandelions going like crazy and all the winter annuals are really taking off,” Brenzil said.

“They could be a fair size when the crop starts coming up and those are going to be the ones that will be the real yield eaters for those crops. Trying to figure out a way to deal with those will be the real challenge,” Brenzil said.

Research conducted at the University of Saskatchewan has shown that the earlier winter annuals and perennials are controlled in the spring in pulse crops, the better off the crop will be.

Brenzil said one particularly telling pulse study had an early herbicide application and then seeding right after, an application at the same time but delayed seeding for two or three weeks, and then a late application and late seeding that was the same seeding date as that treatment with early application and late seeding.

“Essentially what they found is the early application late seeding yielded as much as early application early seeding, and it was the late application late seeding that was the one that suffered as a result of weed competition,” Brenzil said.

He said the growers have been told over and over that early seeding creates better yield, however it may be the early weed control associated with the early seeding that actually creates the better yield.

“I would suggest that the research at the U of S is suggesting that it’s the early weed control that’s paying the benefits and that the early seeding date can be flexed a little bit,” Brenzil said.

The Saskatchewan Guide to Crop Protection provides information on herbicides, fungicides and insecticides registered for control of weeds, plant diseases and insects.

Submissions for the guide are due by late November, but there are sometimes products that achieve registration after this date. This year for pulse crops there are two products that growers can use that didn’t make it into the guide.

“For burn downs, Goldwing has the option of seeding lentil, chickpea, lupin, dry bean or fababean after use. And the other thing that came across our plate after the fact is small red and large green lentils could be added to spring application of Valtera,” Brenzil said.

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