A switch to conservation tillage practices is generally a good thing, but new weed species can present new control challenges.
“As growers change to conservation tillage, they often see a change from the usual annual weeds, such as wild oats and pigweed, to hard-to-control annuals and winter annuals, such as narrow-leaved hawk’s beard,
cleavers, perennial Canada thistle, and both perennial and annual sow thistle,” says agronomist John Mayko with ARTI Linkages in Mundare, Alberta.
Research at the Indian Head Experimental Farm in Saskatchewan shows that weed population changes do not result solely from a change to conservation tillage. Weed populations are influenced by cropping practices, weed control with tillage and weed control with herbicides. Herbicide use and adherence to crop rotation schedules will both affect the weed spectrum and population, as does the tillage system. Minimum and zero tillage carry the
potential for reduction of broadleaf weeds but may increase the incidence of volunteer crops as weeds. Herbicide-resistant weeds pose a special set of challenges.
The dreaded resistance problem
Herbicide-resistant weeds continue to top the conservation tillage farmer’s list of weed worries. In Western Canada, resistant weeds tend to be green foxtail, wild oats, kochia, chickweed and false cleavers. In the U.S. weeds of concern tend to be cheatgrass, wild oats and kochia – with a suspected increase in green foxtail resistance now reported in North Dakota.
“Several effective herbicides are available for controlling downy brome in wheat, but developing resistance to one of these herbicides with one mode of action makes all of them ineffective,” says Mike Moechnig, South Dakota State University Extension Weeds Specialist at Brookings. “Including rotational crops will not only break up the winter annual life cycle of downy brome, but also enables the use of alternative herbicide modes of action.”
Moechnig says that some producers are discovering they have glyphosate-resistant kochia and common ragweed. The best defences are development of a record-keeping strategy that accurately records the chemical Group and strict adherence to herbicide and crop rotations.
If you rent a tract of land, make sure you know what you’re getting into. Both Mayko and Moechnig agree that an accurate herbicide history can help the producer avoid the possibility of herbicide carryover injury to crops. Moechnig says, “Herbicide-resistant weeds can increase weed control costs by $10 to $20 per acre.”
Both Mayko and Moechnig believe that two recent trends in farm management are helping to intensify the problem of resistant weeds. Those two trends are declining soil disturbance due to reduced tillage and direct seeding, and the rapid increase in farm size.
Mayko says that increasing farm size poses weed management risks. “With fewer people managing much larger land bases, changes are needed in how fields are assessed,” he says. “We routinely see farmers explore fields on quads, but what’s surprising are the numbers of farmers scouting from ultralight aircraft.”
Pesky Brome weeds aren't going away
Reduced tillage is helping to promote the growth of brome grasses. Downy brome thrives under no-till production because the seed is no longer buried deep in the soil. Leaving brome weeds to their own devices spells yield loss. If you’re a winter wheat grower, watch out. Winter wheat is a poor competitor.
Solutions are available
An application of glyphosate prior to crop emergence either in the spring or in the fall for winter wheat is a good choice. Growers can choose to tank mix glyphostate with Pre-Pare™ herbicide that offers longer lasting weed control than glyphosate alone. Everest® is registered for control of Japanese brome and suppression of downy brome in the U.S.; and control of wild oats resistant to Group 1 herbicides. (Everest is not registered for control of Japanese Brome in Canada.)
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A switch to conservation tillage practices is generally a good thing, but new weed species can present new control challenges.
“As growers change to conservation tillage, they often see a change from the usual annual weeds, such as wild oats and pigweed, to hard-to-control annuals and winter annuals, such as narrow-leaved hawk’s beard,
cleavers, perennial Canada thistle, and both perennial and annual sow thistle,” says agronomist John Mayko with ARTI Linkages in Mundare, Alberta.
Research at the Indian Head Experimental Farm in Saskatchewan shows that weed population changes do not result solely from a change to conservation tillage. Weed populations are influenced by cropping practices, weed control with tillage and weed control with herbicides. Herbicide use and adherence to crop rotation schedules will both affect the weed spectrum and population, as does the tillage system. Minimum and zero tillage carry the
potential for reduction of broadleaf weeds but may increase the incidence of volunteer crops as weeds. Herbicide-resistant weeds pose a special set of challenges.
The dreaded resistance problem
Herbicide-resistant weeds continue to top the conservation tillage farmer’s list of weed worries. In Western Canada, resistant weeds tend to be green foxtail, wild oats, kochia, chickweed and false cleavers. In the U.S. weeds of concern tend to be cheatgrass, wild oats and kochia – with a suspected increase in green foxtail resistance now reported in North Dakota.
“Several effective herbicides are available for controlling downy brome in wheat, but developing resistance to one of these herbicides with one mode of action makes all of them ineffective,” says Mike Moechnig, South Dakota State University Extension Weeds Specialist at Brookings. “Including rotational crops will not only break up the winter annual life cycle of downy brome, but also enables the use of alternative herbicide modes of action.”
Moechnig says that some producers are discovering they have glyphosate-resistant kochia and common ragweed. The best defences are development of a record-keeping strategy that accurately records the chemical Group and strict adherence to herbicide and crop rotations.
If you rent a tract of land, make sure you know what you’re getting into. Both Mayko and Moechnig agree that an accurate herbicide history can help the producer avoid the possibility of herbicide carryover injury to crops. Moechnig says, “Herbicide-resistant weeds can increase weed control costs by $10 to $20 per acre.”
Both Mayko and Moechnig believe that two recent trends in farm management are helping to intensify the problem of resistant weeds. Those two trends are declining soil disturbance due to reduced tillage and direct seeding, and the rapid increase in farm size.
Mayko says that increasing farm size poses weed management risks. “With fewer people managing much larger land bases, changes are needed in how fields are assessed,” he says. “We routinely see farmers explore fields on quads, but what’s surprising are the numbers of farmers scouting from ultralight aircraft.”
Pesky Brome weeds aren't going away
Reduced tillage is helping to promote the growth of brome grasses. Downy brome thrives under no-till production because the seed is no longer buried deep in the soil. Leaving brome weeds to their own devices spells yield loss. If you’re a winter wheat grower, watch out. Winter wheat is a poor competitor.
Solutions are available
An application of glyphosate prior to crop emergence either in the spring or in the fall for winter wheat is a good choice. Growers can choose to tank mix glyphostate with Pre-Pare™ herbicide that offers longer lasting weed control than glyphosate alone. Everest® is registered for control of Japanese brome and suppression of downy brome in the U.S.; and control of wild oats resistant to Group 1 herbicides. (Everest is not registered for control of Japanese Brome in Canada.)
Write a comment
- Required fields are marked with *.