Chemical Options For Controlling Invasive Species On Pasture

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There was a time when the foothills area of southeastern Alberta was an ocean of grass with barely any brush or even a weed in sight anywhere. Not so today, about 120 years later. It’s been said that in many areas 30 per cent or more of the old rangelands have been lost to weed infestation and brush encroachment. That’s a huge loss of productive land available to livestock for grazing.

A recent media helicopter pasture tour of the foothills area west of High River, sponsored by Dow AgroSciences, showed participants a stark perspective of the extent of the takeover of the traditional rangelands by invasive plant species.

Ranchers, landowners and leaseholders have watched the loss of these famous grasslands with almost no recourse to stop it. The past preservation of natural grasslands was by means of extensive range fires and intensive grazing by millions of bison. Those preservation methods are no longer available as the bison are long gone, and the last major range fire was in 1936, it spread from the U.S. border to north of Cochrane.

Some techniques have been tried to control unwanted encroachment such as controlled burning, mechanical removal and even prescription sheep grazing. All those methods can have some impact, but they have not proven practical on a large scale for several reasons. Meanwhile the incremental loss of grassland continued each year.

Few options

The development of modern herbicides to control unwanted vegetation has been the one hope to not only stop encroachment but to actually see grassland returned to grazing availability. But its widespread use has been a slow process. Herbicide manufacturers have usually focused on developing control products for the larger and more lucrative grain and oilseed sector.

“There haven’t always been effective herbicides that were specifically designed for controlling weeds and brush on pastures,” said Brian de Kock of Dow AgroSciences.

Products have been available that used 2,4-D as an active ingredient but its control range was limited and only effective on a few weeds for a relatively short time. It worked but users were expecting more dramatic results. That’s changed, said de Kock. Dow has released Reclaim, a tank mix of 2,4-D with another Group 4 active ingredient, aminopyralid. They are already copackaged in another Dow Agro range and pasture tank mix, Restore, but the aminopyralid component in Reclaim also includes metsulfuron-methyl, a Group 2 active ingredient in products such as DuPont’s Express Pro, Escort and Ally.

The product’s label covers it for extended control of western snowberry (buckbrush), prairie wild rose, shrubby cinquefoil, silverberry (wolf willow), Canada thistle, dandelion, pasture sage (fringed sage) and prairie sage in rangeland and permanent pasture.


From the outside the herbicide approach looks like the ideal solution to the insidious problem of continuing loss of productive grassland, particularly since nothing else seems to work. But according to de Kock, ranchers have been reluctant to use chemicals.

“Farmers have been long time users of products to control pests, weeds and diseases in their field crops. They have the expertise and the equipment, ranchers don’t readily have that,” he said.

There is also the matter of economics. Herbicide products can look to be costly to livestock operators who are not used to pencilling out productivity. Results are not always immediate and are more long term when per-cow and per-acre production are considered.

“We can prove through our test and control plot comparisons that our products work and can be economic, but the rancher remains reluctant, we need to overcome that,” de Kock said.

At a tour stop at the Spruce Grazing Co-op, the reality of herbicide use comes to light. “We use about $5,000 worth of herbicide on our pastures to control weeds and brush,” said Dan Smith, a co-op director. “We know the product works but that’s all we budget for.”

That figure is unlikely to change as long as co-op members do not see a significant reduction in their cattle allotments due to loss of pasture from invasive weeds and brush. “When members start seeing fewer cattle permits and start asking why, and it’s because of brush and weeds, only then will we see a push for more control on pastures,” said Joe Engelhart, co-op herd and pasture manager.

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