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New Herbicide Does a Number on Pasture Brush
Dow AgroSciences - April 24, 2001
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In pastures getting overrun by willow and poplar, a herbicide which has been used for some time by the forest industry is doing a good job of controlling woody vegetation that chokes out grazing land.
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RANCHER MURRAY HOLT likes the idea of controlling brush and aspen on pasture with a one-pass herbicide treatment for about $60 per acre. Clearing, farming it up, and reseeding would cost $250.
That's why Holt, president of the Connor Creek Grazing Association northwest of Edmonton, is anxious to treat another 300 acres of tree-encroached pasture this spring to see if a newly registered herbicide from Dow AgroSciences really is the way to control brush on pasture.
The product, Remedy, was used in a demonstration project to treat about 40 acres of pasture on the 30,000-acre Connor Creek Grazing Reserve in 2000. A one-pass application, applied in early July by a sprayer-equipped helicopter at a rate of 2 liters per acre in 5 gallons of water, appears to have done the job.(Remedy was aerially applied under a research permit in 2000. Full registration for aerial application is expected in 2001.)
"We'll have a better idea this year," says Holt. "But it appears that we got between 90% and 95% control on brush with just that one treatment. If it worked as well as we think, it's an excellent tool for keeping pastures in production." Remedy appeared to give nearly 50% more brush control than the 2,4-D applied in other plots.
The Connor Creek reserve, which lies in the Parkland Region of Alberta, is a productive privately-managed public pasture for about 9,400 head of cattle owned by 84 producers in the Sangudo/Mayerthorpe/Barrhead area. Divided into about 40 pastures, the area includes about 22,000 acres of developed pasture.
Along with the challenge of keeping nearly 10,000 head of cattle fed, watered and healthy on this sprawling range with varying severity of terrain, managers struggle to keep their grass productive. The reserve, claimed from the mostly-aspen forest nearly 30 years ago, has a tendency to return to its roots.
"You just see a little more brush every year," notes reserve manager Duane Edge, whose job includes co-ordinating 6 different rotations each with 600 cow/calf pairs. Willow, poplar, rose, aspen and other brush species try to re-establish on pastures seeded to timothy, brome, fescue and orchard grass. "Some pastures are really overgrown with patches of trees and brush 15' to 20' tall," he adds.
How to control forest regeneration is the big issue. Blading or shearing it off and windrowing with a crawler tractor is one option. Breaking up the fields, plowing, discing and reseeding is another. Treatment with a brush-controlling herbicide is also a possibility.
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"Before" and "after" shots (above) show an excellent kill of well-established woody brush.
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Ground fires can be used to control brush, too. But pastures may have to be taken out of production or rested to allow enough grass litter to accumulate to carry the fire and, of course, the politics of burning have to be considered.
With any treatment, cost and effectiveness are key factors for the association. Even shearing and discing can cost nearly $140 per acre, and often the activity stimulates more suckering and regrowth that brings the brush problem back in a few years. Farming the land and re-seeding will hold back regrowth for a while, but it costs about $250 per acre and obviously takes land out of production until new grass is established.
Herbicide treatments are an option, but the product has to be effective on a wide range of vegetation while selective enough to not harm the grass. That's the nice feature of Remedy, points out Tyler Groeneveld, range and pasture specialist with Dow AgroSciences in Calgary. He coordinated the Connor Creek demonstration project last year.
Remedy controls a wide range of shrubs and trees as well as several perennial broadleaf weeds. But it doesn't hurt timothy, brome, fescue and orchard grass growing under the brush and tree stand.
"We were able to graze the pasture, then spray the brush and be back in there within 4 to 6 weeks without missing a beat in the pasture rotation," notes Edge. While the herbicide also appeared effective on taller trees and shrubs up to 15' or more in height, ideally the best coverage and control is on vegetation in the 12" to 5' height range, or at least on shrubs under 8'.
Remedy can be applied at anywhere from 1.6 to 3.2 liters per acre to control 17 common woody plants including alder, ash, aspen, birch, buckthorn, cottonwood, poplar, wild rose, and willow to name a few. Among the 11 broadleaf weeds it's registered on are burdock, chicory, dandelion, ragweed, smartweed and vetch.
At less than the 2-liter rate there are no grazing restrictions for beef cattle, and a
14-day withdrawal period after spraying for dairy cattle. At application rates over 2 liters per acre, beef cattle should be held off pasture for 14 days and dairy cattle for 60 days. If you're treating less than 25% of the pasture, however, there are no restrictions for beef cattle at any rate.
"Farming up the pastures to control brush isn't an economical option," points out Holt, who ranches near Sangudo. "And because some brush and tree patches are getting quite tall and the terrain can be pretty rough, we needed a herbicide that could be applied aerially as well."
In the Connor Creek demonstration, the product was applied to several 5- to 8-acre patches of brush in different pastures. At 2 liters per acre, herbicide cost was about $46 while application was about $14.
"Our assessment last fall was that it appeared to have had good control on trees and shrubs without affecting the grass and without leaving a soil residue," says Edge.
Remedy is expected to have a good fit as a brush control product across the aspen/parkland region of the prairies, points out Groeneveld.
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