Crop rotation vital to slowing resistance in weeds

One of the banes of a farmer's existence is weeds, unwelcome plant-life that sinks in its roots, sucks up moisture and nutrients, and...

One of the banes of a farmer’s existence is weeds, unwelcome plant-life that sinks in its roots, sucks up moisture and nutrients, and denies the crops energy needed to grow robust and strong.

Since the 1930s, farmers around the globe have been able to control weeds – a term which refers widely to all unwanted plants, not just official “weed” species – but herbicide resistance is increasingly becoming a problem, according to Harry Brook, crop specialist with the Alberta Ag-Info Centre in Stettler.

Some weeds are the accidental offshoots of previous crops, the volunteers left behind from a previous year, or blown in the wind. With so many crops today being hybrids that offer some sort of resistance to herbicides, these volunteers are notoriously difficult to exterminate, Brook said.

“When you have roundup-resistant canola volunteers in a field, glyphosate won’t kill it,” Brook said. “It will be there, competing with the new crop.”

Five years ago, a strong wind from an unexpected quarter sent swaths of canola rolling across fields through central Alberta. Seed pods burst open and spilled canola seeds across fields.

In situations like that, volunteers are almost guaranteed to be a problem, Brook said. And, while hybrids do not “breed true,” there’s still the possibility they will germinate.

When it comes to genuine weeds, resistance is increasing year over year.

The kochia plant is one such example of a plant that has become extremely tolerant of several categories of herbicides. While kochia is not big an issue in central or northern Alberta at this time, the tumbling weed is becoming a nuisance in southern Alberta.

“The plant grows, then separates from the stem,” Brook explained. “The tumbleweed rolls around, spilling seeds everywhere as it goes.”

With Alberta’s windy prairies and rolling hills, tumbleweeds can go quite the distance.

In central Alberta, one of the more common weeds that is becoming a nuisance due to herbicide resistance is wild oats, Brook said.

“You won’t find a whole field full of resistant wild oats,” Brook said. “But there’s increasing amounts, and the number climbs every year.”

Herbicides are broken into different classes depending on the method in which the herbicide kills the weeds. Some outright kill weeds, while others prevent the weed from maturing. Others not only kill the weed itself, but migrates through to the roots to ensure the weed does not re-sprout.

Resistances to herbicides have varying degrees. In some cases, the herbicide kills the weed too quickly, before the herbicide can migrate into the roots. This means that though the weed dies, the roots continue to drain moisture and nutrients from the soil and will sprout anew. In other cases, the effect of the herbicide is lessened, or out-right eliminated by the weed’s resistance.

Other weeds will winter well and sprout in the spring before herbicides have been put down, spreading their wealth of seeds before farmers can even get out in the field.

Farmers can help control herbicide resistance in weeds by rotating crops and herbicide types more frequently, Brook said.

“Many farmers use type one or type two herbicides,” he said. “They’re cheap, but a lot of weeds are becoming resistant to those types.”

Resistance to type one is about 15 per cent and growing annually, while in type two, the resistance is at about 25 per cent, and growing.

By using different herbicides, and not swapping between types one and two every other year, weeds will have a harder time building up the resistance that is increasing the difficulty in eliminating weeds from farmers’ fields.

Just Posted

Watch: Gravel truck turns into wrong off-ramp at Highway 2 Ponoka

The new Highway 2 and Highway 53 intersection at Ponoka caused some confusion for one driver

Stettler armed robber convicted in court Oct. 12

Jayson Marshall gets over two years in jail

CORRECTED Donalda Creamery plans on tap Oct. 23

Architects to answer public’s questions about plans

WATCH: ASIRT investigating officer-involved shooting during crime spree

Shots fired on two occasions during incidents, one suspect remains in hospital with serious injuries

Drumheller RCMP investigate human remains

Police find human remains in burning vehicle near Morrin

VIDEO: Tragically Hip singer-songwriter Gord Downie dies at 53

Downie had been fighting brain cancer for over a year

WATCH: 10,000 signatures gained to stop ‘no pets’ rental policy

Pets OK BC said about 1,700 animals were surrendered to the BC SPCA last year due to housing issues

VIDEO: Oprah Winfrey and a celebrities attend ‘B.C. Miracle Concert’

Fundraiser featured Foster, Steven Tyler, The Tenors, Matteo Bocelli, Laura Bretan, Carly Rae Jepsen

Search ramps up for B.C. woman after dog, car found near Ashcroft

Jenny Lynn Larocque’s vehicle and dog were found in Venables Valley, but there is no sign of her

Police officer hit by car, stabbed in Edmonton attack back on job

Const. Mike Chernyk, 48, returned to work Thursday

Berry disappointed: Bear tries to eat fake fruit on woman’s door wreath

A Winnipeg woman has taken her berry-embellished wreath down, after a hungry bear visited her porch

All three victims identified in Fernie arena ammonia leak

Wayne Hornquist and Lloyd Smith were from Fernie and Jason Podloski from Turner Valley, Alta

4 B.C. prisons install body scanners to combat drug smuggling

The scanners are aimed to combat the smuggling of contraband including weapons and drugs

Outspoken Mountie assigned to admin duties for refusing to shave goatee

The 15-year veteran of the force said he believes the RCMP is targeting him

Most Read


Weekly delivery plus unlimited digital access for $50.40 for 52 issues (must live within 95 kilometers of Stettler) Unlimited Digital Access for one year for $50.40 Prefer to have us call you? Click here and we’ll get back to you within one business day.