Crop Advisor’s Casebook: What caused this 80 per cent loss in canola?

A Crop Advisor's Solution from the February 21, 2017 issue of Grainews

Seven days after Ken sprayed his herbicide-tolerant canola crop, most of the plants in one field were dead or dying.
Jason Sauchuk. photo: Supplied

Ken, a central Alberta producer who farms 2,000 acres of cereals and oilseeds, in addition to 150 head of cattle, called me after he discovered 80 per cent of the canola plants he’d seeded in one field were dead in the seed row. He thought the problem might be a sprayer issue, since a prominent line marked out areas of injured and uninjured plants in this field. It was also the last field to be sprayed, he told me.

Now, seven days after spraying his herbicide-tolerant canola crop, most of the plants in one field were dead or dying, the symptoms appearing five days after he’d initially sprayed, Ken said.

As I checked the plants, I found other symptoms, such as mottling of the leaves, possibly caused by marginal chlorosis and necrosis where the leaf surface had been in contact with the herbicide. The plants were also starting to turn white and crispy.

There was, indeed, a clear line in the field marking areas of healthy and unhealthy plants, where a new tank of herbicide could have been started. Beyond the line, to the north, the canola plants were developing normally, as were the rest of the plants in Ken’s canola fields.

To untangle this puzzle, we began by reviewing records, such as soil test results gathered the previous fall, which indicated adequate levels of nutrients were present in the soil.

Leaves were mottled, possibly due to marginal chlorosis and necrosis where the leaf surface had been in contact with the herbicide. The plants were also starting to turn white and crispy.

We then reviewed environmental and soil conditions that growing season. Generally, all fields had been treated in the same manner, Ken said. He’d applied a herbicide as a pre-seed burndown on all fields before planting the canola.

From there, seedling emergence and growth appeared normal. Two days after Ken sprayed his fields, the area received about one centimetre of rain. Up to that point, it had been a drier spring, with little precipitation.

Because all fields were treated in a similar manner, we could eliminate many factors as the cause of injury. For example, all fields had received the same amount of moisture before seeding, during the first weeks of development, and after spraying the crop. Thus, since all other fields were healthy, soil moisture was not the cause of injury.

Likewise, before seeding, all fields had adequate levels of nutrients for plant growth, and fertilizer tubes on the drill were unplugged and in good working order. All other fields, except this one, were thriving; thus, fertility was not the problem.

All fields were seeded to wheat the previous year, and no residual herbicides had been used, so herbicide carryover from the previous crop could also be ruled out. Herbicide carryover from the pre-seed burndown was also unlikely because no other fields had suffered injury, yet all fields had received the same herbicide application.

I didn’t think this was a sprayer issue, either, because the sprayer did not appear to have any mechanical issues. In addition, this was not the first field to be sprayed, and only a portion of this one field was damaged, whereas all other fields were just fine. Also, I reviewed Ken’s tank cleanout procedures, and I thought the risk of herbicide injury due to chemical residue in the tank was low.

Yet, all clues in this field — the injured leaves and prominent line separating damaged and undamaged plants — pointed to herbicide injury.

One other factor I thought we’d best eliminate was an issue with the seed. I suggested we track down and review seed lot numbers and seed tags. We could also check with the supplier if any other producers were reporting issues with this seed lot.

It was while we were looking over the seed lot numbers and seed tags that we spotted the problem.

It took a while to get there, but it was these records that shed light on Ken’s canola conundrum.

Crop Advisor’s Solution: Not paying attention to detail could take a bite out of your profits

Once we reviewed the records, the answer seemed obvious — Ken had planted two different types of herbicide-tolerant canola seed in the same field, which employ two different chemistries.

It was the previous fall that Ken planned to seed two different herbicide-tolerant canola varieties (paired with two different chemistries) to clean up a dirty quarter section the following spring.

Ken forgot to consult his cropping plan for that season and, unknowingly, planted two different varieties in the last field, thinking he’d only planted one. He applied one herbicide to all fields, thus, the last field, planted with the second variety, was sprayed with the wrong herbicide, killing 80 per cent of the plants in that field.

Ken left the affected area as fallow, as it was too late in the season to re-seed. He now keeps and consults excellent cropping plans and crop management records to avoid similar incidents in the future.

Jason Sauchuk works for Richardson Pioneer in Sprucefield, Alta.

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