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Consider Fall Weed Control

The wet spring didn’t just delay or prevent seeding, it spawned unusual weed problems, including one relatively new to Manitoba called Northern willowherb (Epilobium ciliatum).

“This year it’s everywhere,” Scott Day, Manitoba Agriculture, Food and Rural Initiatives’ (MAFRI) diversification specialist in Melita, said in an interview Aug. 25. “You have areas of fields where it looks like it’s solid willowherb. It’s kind of like a little shrub and so it’s not all that easy to kill with glyphosate.”

Day, who also farms, said he never saw Northern willowherb until last year, which was also wet.

Northern willowherb is native to North America and prefers wet, shaded areas, said Robert Gulden, assistant professor weed science at the University of Mani toba. He isn’t sure yet whether it’s an annual or perennial weed. It could depend on its environment.

It’s also unknown whether willowherb will continue to be a problem in cropland that gets seeded in the future under drier conditions.

“It’s a tenacious weed this year for sure,” Day said. “It’s amazing how it has just shown up everywhere.”

TENACIOUS

Almost three million acres in Manitoba went unseeded this spring because the land was too wet. Most of them are in the southwest, said MAFRI’s weed specialist Nasir Shaikh.

“Most of those three million acres are loaded with weeds,” he said. “The spring was wet, they had plenty of water and it was fairly warm and the weeds took advantage.”

Barnyard grass, thistles (Canada, sow and nodding), pigweed, cleavers, narrow-leaved hawk’s beard, curly dock, flixweed, shepherd’s purse and Canada fleabane are some of the main weeds farmers have in their fields now, he said. Canada fleabane is of interest because a glyphosate-tolerant biotype has been confirmed in Ontario.

A lot of foxtail barley is showing up around Manitoba too, especially on saline soils.

Many farmers sprayed their weedy, unseeded land earlier this season, but it should be done again to kill weeds missed earlier and control winter annuals, Shaikh said.

GREEN MANURE

He suggests if weeds haven’t gone to seed yet farmers turn them into green manure by mowing.

One of the biggest weed problems in the southwest is volunteer Roundup Ready canola, Day said. They grew fast and got too big to be controlled with herbicides added to glyphosate.

“That has probably been the No. 1 concern for farmers planting winter wheat,” he said.

MAFRI is recommending farmers apply 2,4-D to control those volunteers, but agronomists are unsure how well it will work on big plants.

Some glyphosate tank mixes, including Heat, Express Pack, Frontline, PrePass and Rustler have not been effective, Day said.

Day also warns because of potentially injurious residues it’s too late in the season to apply certain herbicides to control Roundup Ready canola if they plan to seed canola on that land next spring.

The southwest is seeing more biannual wormwood, Canada fleabane, and wild buckwheat this year, Day said.

“And redroot pigweed has just started growing like crazy everywhere.”

“Those are weeds that traditionally are not a problem in the area but have certainly come about this year and controlling them now is a good idea before they get too big and turn into biannual weeds,” Day said.

SLOW DOWN

Glyphosate won’t work as well when applied under dusty conditions, he added. To reduce dust farmers should spray in the evening or morning or slow down.

“If you’re making a lot of dust you really shouldn’t be in the field,” he said.

“I guess the bottom line is we’re still getting good, effective control using glyphosate. Even if you have a really bad mess out there don’t worry, we seem to be able to keep things under control.”

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About the author

Reporter

Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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