Dandelions are a perennial plant that can easily become a perennial problem.
With their brilliant yellow blossoms, they are well known on the Prairies. But they’re not well loved once they get established in fields.
This spring farmers have an added tool to consider when fighting dandelions.
Amitrol 240 was registered this year for use on wheat, barley, canola and field peas in Western Canada.
“It’s particularly effective on dandelions, whether they’re overwintered seedlings or perennial dandelions,” said a spokesperson for Nufarm Agriculture Inc., a company marketing the product in Western Canada.
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For farmers using herbicides to control dandelions, one of the best times to attack the plant is in the fall.
As the plant draws reserves into its roots for the winter, it also draws in the chemicals that can kill it.
“You’re going to get better control in the fall because you’re going to be attacking the root system,” said Kim Brown, a Manitoba Agriculture weed control specialist.
Alberta Agriculture describes pre- or post-harvest glyphosate as effective for controlling dandelions if the weeds are growing when the herbicide is applied. According to the department, 2,4-D applied after harvest will suppress them.
A pre-seed burndown using glyphosate or 2,4-D is also used by producers. While that will help suppress dandelions, Brown said a pre- or post-harvest application of herbicide is still more likely to offer control of the weeds.
In the case of serious infestations, producers might want to use in-crop herbicides to limit the dandelions’ seed production, said Kent Shewfelt, president of the Manitoba Weed Supervisors Association.
Crop rotations also should be considered to incorporate plantings that are more competitive with dandelions.
“You have to figure out what all is in your toolbox and make use of all your tools,” Shewfelt said.
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Amitrol 240 is a slow-acting chemical that stops photosynthesis. Plants treated with the product turn white, then purple and eventually take on a charcoal color as they wilt away.
Nufarm estimates that as many as six million acres of forage and annual crop land in Western Canada are infested with dandelions, with perhaps half of that requiring some form of treatment.
Amitrol 240, applied at a rate of 1.7 litres per acre, costs about $10 for each acre treated.
That is more expensive than the typical cost of a pre-seed burndown with glyphosate, said the Nufarm spokesperson. However, Amitrol is meant to control dandelions rather than only suppress them.
Tillage also helps to keep dandelions in check by breaking up their tap roots. Among the fields more susceptible to dandelions are those in minimum tillage systems.
“If you don’t deal with them, the problem tends to perpetuate itself,” said Byron Irvine, a research scientist at Agriculture Canada’s Brandon, Man., research centre.
For more information about the herbicides used to treat dandelions, Manitoba and Saskatchewan farmers can consult their crop protection guides. In Alberta, the guide is known as the blue book.
