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Crop Advisor’s Casebook: wild oats can’t be tamed

Last July, while sitting in his tractor cab all set to apply an in-crop fungicide to his durum field, Peter was surprised to see wild oat heads popping out of his crop canopy. To make matters worse, while swathing his canola, he found small patches of wild oats growing in that field as well.

Later that season, Peter and I took a ride in his combine to investigate the appearance of the wild oats in his fields. Peter produces 5,000 acres of wheat, canola and lentils near Rouleau, Sask. “I don’t think the herbicide I applied earlier this year is working — my wild oats aren’t being controlled,” he said. “I need some options for next year.”

From the cab, I could see small patches of wild oats located randomly throughout Peter’s durum crop. We also found small patches of wild oats where they had taken over in Peter’s canola crop after it had been swathed.

Could Peter have missed areas of his fields with his sprayer during herbicide application, or had there been an equipment failure of some kind? Or, perhaps environmental conditions at the time of spraying had decreased the efficacy of the in-crop herbicides Peter had applied to those fields.

According to the sprayer monitor, Peter had not missed any areas with the herbicide on either field. Because the wild oats were appearing in random patches in his fields and not in rows or strips, the problem was likely not a plugged nozzle or boom. Together, we also checked weather records and environmental conditions at the time of spraying, but nothing appeared out of the ordinary.

Peter had applied a Group 1 herbicide to both fields. He had used clethodim on his canola crop and clodinafop-propargyl on his durum. “They’ve worked fine every other year I’ve used them,” he said. We examined his durum field more closely. Here and there, random patches of wild oats dotted the field; after a thorough scout, however, I noticed that all other areas in the field were showing good control of the wild oats.

Peter had a growing problem in his fields, one he’d nurtured for the past few years, but like many farmers in Western Canada, he didn’t know it.

“Your in-crop herbicide is working,” I said. “But getting rid of the wild oats in your fields is going to take forethought and planning.”

Why are some of the wild oats in Peter’s field growing through the Group 1 in-crop herbicide he had applied earlier in the growing season? What can he do to get rid of the wild oats in his canola and wheat fields? Send your diagnosis to Grainews, Box 9800, Winnipeg, MB, R3C 3K7; email [email protected] or fax 204-944-5416 c/o Crop Advisor’s Casebook. Best suggestions will be pooled and one winner will be drawn for a chance to win a Grainews cap and a one-year subscription to the magazine. The best answer, along with the reasoning which solved the mystery, will appear in the next Crop Advisor’s Solution File. †

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