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Crop Advisor’s Casebook: Giant canola a puzzle

A Crop Advisor's Solution from the January 6, 2015 issue of Grainews

Andrea Astleford
Andrea Astleford photo: Supplied

Back in mid-July, I was contacted by two farmers in the Colonsay area southeast of Saskatoon, Sask. Tyler and Steve called to complain about essentially the same thing — both growers were seeing very large canola plants scattered randomly throughout some of their canola fields.

“What are these rogue plants in my field?” asked Tyler, who like Steve grows canola, wheat, peas and occasionally soybeans on his farm. “I don’t know why they’re there, and I’d sure like some help figuring this out.”

When I drove out to the two farms to have a look for myself, it was easy to spot the giant plants among the canola crop, which was in full bloom. They were taller, stalkier and generally bigger than the rest of the plants in the fields. I was told the rogue plants had started flowering later than the rest of the canola and that there were no pods with seeds being formed.

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I checked the field edges as well as high and low spots to see if there were more or less of these large plants there, but like Tyler and Steve, I could detect no observable pattern to the giant canola.

While the plant distribution was random, I did notice that some of the giant canola contained more root maggots than the rest of the crop. However, disease pressure appeared to be consistently low throughout all of the canola fields, with no obvious differences between those areas with rogue plants and those without.

It was only when I enquired into the variety of canola in both farmers’ fields that I began to zero in on the source of the problem.

While the plant distribution was random, some of the giant canola contained more root maggots than the rest of the crop.
While the plant distribution was random, some of the giant canola contained more root maggots than the rest of the crop. photo: Supplied

Crop Advisor’s Solution: Off-type seed source

I did notice that some of the rogue plants contained more root maggots than the rest of the crop, but I quickly discounted this as a source of the problem. Severe root maggot damage on a plant would typically cause it to wilt and eventually die, not make the plant bigger or more robust.

Disease pressure was also ruled out, so if it wasn’t anything in the environment that was causing the giant canola, what was?

The answer to that question lay in the seed. Tyler and Steve informed me that they had planted the same canola variety, and that in fact their seed supplies had both come from the same lot number.

We contacted the seed representative, and after the company did some additional testing it was confirmed that the specific batch from that variety contained some off-type seeds, which are part of the hybrid production process, mixed in with it. It was these off-type seeds that had produced the large, sterile plants and created the non-uniformity in the canola crop.

Fortunately for Tyler and Steve, their canola yields were not affected. We checked the number of off-type plants in one small field area to estimate a percentage of the canola affected, and this percentage turned out to be so small it was determined that there would be no issue other than the appearance of the crop. A similar test by the seed company produced a percentage figure that coincided with ours.

In the end, there wasn’t really anything either farmer could have done to prevent the rogue canola from showing up, since there’s always a chance some off-type canola seed will be mixed in with the variety you buy. However, it’s a good idea for growers to be aware of this possibility, and to check their fields regularly for abnormalities that, if enough plants are affected, could possibly threaten crop yield or quality.

Andrea Astleford is a sales agronomist with Richardson Pioneer Ltd. at Saskatoon, Sask.

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