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Crop Advisor’s Casebook: What’s stalling this canola?

A Crop Advisor's Solution from the June 2011 issue of Grainews

Joe grows 11,000 acres of wheat, barley, canola and peas on a mixed farm near Moose Jaw, Sask. While on a routine scout, he noticed some of his canola fields weren’t filling in as quickly as the others. “I may have seeded too deep, or it could be cutworms,” he told me. When he walked through the affected fields there was nothing obviously wrong — there were still lots of canola plants emerging — but he thought I should take a look, he said.

The first thing I noticed at Joe’s farm was a difference in the stages of canola seedling emergence between his fields. Overall, five different fields totalling 1,000 acres were showing delayed emergence while another 2,000 acres appeared normal. The normal-looking fields were more advanced than the others, even though some of them had been seeded later.

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Most of the plants in the fields showing delayed emergence were stalled at the one-leaf stage, whereas plants in the healthy fields were already at the three-leaf stage.

We had our work cut out for us; delayed seedling emergence like this could be the result of any of the following causes: seeding depth, fertilizer application, herbicide residue, seedling disease, or insects — to name a few causes. To complicate matters further, Joe had seeded three canola varieties, so seed lot and varietal differences also had to be considered.

Initially, Joe felt concerned that he may have seeded too deep with one drill, but I checked the seeding depth and reassured Joe it was fine. At this time, I also noticed the roots of the plants were a healthy white colour, ruling out seedling blight and wireworms as factors causing the damage in Joe’s fields, and I couldn’t find any evidence of cutworms.

There was no pattern to suggest the damage correlated to a specific seed lot or variety because all five of the affected fields were damaged in a similar manner.

That year, Joe’s application of fertilizer went off without a hitch. He had seed-placed 90 pounds of balanced fertilizer product including nitrogen, phosphate and sulphur, so fertility levels should have been adequate.

I could also rule out herbicide carryover as a cause of the damage to Joe’s canola plants because some of the affected fields had not had any residual herbicides applied the previous year.

I re-entered one of the affected fields for a closer examination of the plants. I noticed a few subtle symptoms on approximately 80 per cent of the seedlings — some of the leaves were cupped and growing abnormally, and the cotyledons were larger and thicker than I would normally see at this stage.

I wondered if Joe had added another herbicide to the glyphosate he had sprayed in the pre-seed burn-off application?

“Some fields had a lot of flixweed, so we threw in one jug of 2,4-D Ester per tank to heat it up,” he told me.

“I know what’s damaged your canola fields,” I said.


Crop Advisor’s Solution: Herbicide residues hamstring canola

Unfortunately for Joe’s emerging canola seedlings, 2,4-D Ester residue remains in the soil for a few days — enough to injure the seedlings.

This herbicide is valuable for controlling winter annuals in the spring, but not before seeding canola. It normally breaks down after a few days when moisture is present, but Joe’s fields remained dry for 12 days after spraying; therefore, when the canola plants emerged, there was enough residue left in the soil from the 2,4-D Ester to injure them. This herbicide should never be used before seeding sensitive crops such as canola or pulses.

On the bright side, adding 2,4-D Ester to his glyphosate to take care of the weed problem in his canola fields didn’t spell disaster for Joe. The affected plants slowly overcame the herbicide injury, but they matured several days later than normal. Joe’s yield decreased by roughly three to four bushels per acre.

This time Joe was lucky — the loss might have been worse had the weather been less cooperative while the fields were in the flowering stage. Together we developed a crop plan for Joe to follow for the rest of the year and into the coming spring in order to avoid a similar incident.

Wes Anderson is an agronomy manager at Richardson Pioneer Ltd. at Regina, Sask.

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