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Another story on Canada fleabane?

Yes, because the message isn’t getting through, and the situation is getting serious

It may seem repetitive, but that’s because the message isn’t changing. Canada fleabane keeps becoming a bigger problem with each passing year. The weed has been the topic of presentations at the Southwest Agricultural Conference dating back to 2012, as well as at FarmSmart Conferences and in a steady stream of weed and herbicide bulletins.

Country Guide has been a part of that information stream, with three consecutive Pest Patrol columns this past winter with advice on how to deal with herbicide-resistant Canada fleabane. There’s also been an increasing sense of urgency expressed by Mike Cowbrough, OMAFRA weed specialist as well as by Dr. François Tardif of the University of Guelph, and Dr. Peter Sikkema from University of Guelph’s Ridgetown Campus.

Now, their sense of urgency is beginning to turn to frustration, and this year, that frustration began to bubble over right from early spring. For instance, at their first joint meeting this year, certified crop advisers (CCAs) and OMAFRA staff specialists renewed their focus on how to deal with Canada fleabane, with much head-scratching among dealers and company reps about why the message isn’t getting through.

One adviser spoke of a wheat field in Elgin County with Canada fleabane plants that had survived harsh winter conditions. Another dealer said a grower he knows has found the weed on his farm, but didn’t believe them to be resistant to glyphosate. Provincial wheat specialist Peter Johnson added that two of the five fields he’d visited before April 15 had fleabane with three-inch rosettes, so it’s little wonder that weed experts are perplexed.

But the reason for their concern goes even deeper.

Extension staff, dealers and retailers had believed they were doing a good job dealing with Canada fleabane in soybeans, and that it was in wheat where fleabane would be getting out of hand.

Yet according to OMAFRA sources, as much as 60 per cent of the glyphosate-tolerant soybean (Roundup Ready) acres planted in Ontario are still sprayed with glyphosate alone. That means increased selection pressure for resistance.

This is surprising given Sikkema’s revelation in May 2013 that Canada fleabane had been confirmed in Huron County, and that there are now biotypes that are resistant to glyphosate with FirstRate (cloransulam-methyl), meaning they’re resistant to two modes of action. In spite of recommendations then that farmers treat all Canada fleabane as though they’re resistant, that message still hasn’t been picked up.

Also adding to the sense of urgency for 2014 was the delayed onset of spring, a point that’s been long forgotten in the warmth of midsummer. But the April 15 meeting was highlighted by a late taste of winter with three to four inches of snow across most of southern Ontario, further delaying normal operations. The weekend previous to the meeting, many wheat growers in the region had been spreading clover in their crops, putting in time before corn planting. And that impatience was actually adding to the difficulty of dealing with Canada fleabane.

Growers were trying to squeeze more activity into a narrowing window, especially in a shortened spring. They were trying to get nitrogen on winter wheat, prepping corn ground with a fertilizer application, followed by discing or cultivating. Where could they find time and opportunity to deal with glyphosate-resistant Canada fleabane, or fleabane that’s resistant to glyphosate plus FirstRate?

What’s left to say?

Regardless of time constraints, the implications are obvious and in many fields, they’re getting worse. For Mike Cowbrough, the situation is beyond frustrating because he knows the implications, and he’s given the presentations, he’s attended the company meetings, he’s posted bulletins, and yet the message only seems to be getting through some of the time.

“What are we going to say at this point?” asks Cowbrough. “It’s an important weed to control and I’ll grant that, but there are plenty of options, and you’re not going to use glyphosate in wheat, so growers are either going to spray wheat or they’re not.”

That’s another issue for farmers — the lack of fall weed management practices that are commonly used. OMAFRA figures indicate roughly 50 per cent of wheat acres receive some form of herbicide treatment, yet only about five per cent of acres receive a fall weed treatment as part of a conventional fall routine. Growers can cite having to squeeze in the harvest of soybeans, planting winter wheat, then harvesting corn, plow-down and where possible, some type of fall fertility program as the priorities in a six- to eight-week fall season. But the stakes for control of Canada fleabane are getting higher.

Incredible numbers

Whether it’s in soybeans or wheat, the message with Canada fleabane is simple: control it early… or else.

With the weed’s ability to produce 58 million seeds per acre, not to mention a seed that parachutes itself into the wind, it’s easy to understand how Canada fleabane has spread north and east in the past year. Prior to 2013, the weed had been confined primarily to counties along the north shore of Lake Erie — from Windsor to Niagara.

The northward migration is an indication that growers are slow to react to the onset of glyphosate resistance in Canada fleabane, and it seems many are treating fleabane with the same kind of denial as soybean cyst nematode.

According to research done in Illinois, fall weed control is essential for wheat, yet it’s almost as important to keep fields clean following harvest. Failure to do either means growers will not stay ahead of Canada fleabane, even under the most brutal winter weather conditions.

“It’s a big issue, and I understand that,” says Cowbrough, citing the three-part series he wrote for Country Guide, followed by this article that will reach farm mailboxes with 2014’s crops. “If this article works as a summary-primer for the season, that’s fine. I just don’t know how to sell this any different.”

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CG Production Editor

Ralph Pearce

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