Up until recently, narrow-leaved hawk’s beard was mostly found in northwest Saskatchewan and along the Alberta border. A 2014-15 weed survey has revealed that the weed has spread to areas outside of these traditional hotspots. Identification and control can both be difficult. For this reason, it is advised that growers — especially those who live in non-traditional hotspots — take a moment to familiarize themselves with management options.
Considered a noxious weed under the Saskatchewan Weed Control Act, narrow-leaved hawk’s beard can be tough to control. Clark Brenzil, Saskatchewan Ministry of Agriculture weed specialist, attributes the weed’s spread to three possible reasons. “One may be the moisture regime that we’ve had over the last few years,” he said. “We’ve had much more moisture than normal, especially in the southern areas.”
Another contributing factor, he said, could be misidentification: narrow-leaved hawk’s beard has a similar-looking weed cousin that is found in the southwestern prairies, green hawk’s beard.
“The real way to tell the difference between the two is when the plant is flowering,” Brenzil said. “Narrow-leaved hawk’s beard’s rosette will have degraded by then, leaving only stem leaves, whereas green hawk’s beard still has a very definite rosette when it’s flowering.”
Brenzil said it is virtually impossible to tell the difference between the two weeds in their earlier stages of growth.
A third contributing factor could be that narrow-leaved hawk’s beard is well suited to reduced-tillage systems. The weed is a prolific seed producer and its seeds are distributed by wind. In untilled fields, seed tends to get caught up in stubble in the middle of the field rather than blow off to the edges of the field.
What makes narrow-leaved hawk’s beard even more complicated is the fact that seeds have little dormancy, so they can germinate to produce new plants soon after they are shed. As a result, seedlings can emerge throughout the growing season. Generally, however, narrow-leaved hawk’s beard acts as a winter annual with seeds germinating in the fall from mid-August until early October if conditions are suitable. Remaining seeds will germinate in the spring once soil temperatures have risen above 5 C.
The best time for scouting winter annuals, Brenzil said, is in the fall or during burn off. “Most producers are going to be doing a spring burn off anyway,” he said. “But they may want to try and ensure that they’re covering off some of these more specialist weeds a little bit better is to make sure they get on their burn-off process as soon as possible in the spring. As soon as you can get equipment on the field and see some green growth coming, get out there and start making your applications.”
Dandelions provide a good indicator, Brenzil said. “If the dandelions have greened up but they haven’t started producing many flowers yet, then it’s the perfect time to be in the field doing your burn off to make sure that you catch some of these more difficult to control weeds,” he said.
“In the case of narrow-leaved hawk’s beard, if you missed that early window, it’s much more difficult to control,” he said.
In this case, another component needs to be added to burn off. “This isn’t a bad policy, in general, just to try and mitigate the risk of glyphosate resistance in any weeds that are out there,” said Brenzil.
New control option
When it comes to controlling narrow-leaved hawk’s beard, Rory Cranston, field marketing specialist at Bayer CropScience, agrees with Brenzil and recommends taking a holistic approach, one that includes both fall management and spring burn off. Failing that, Cranston pointed to another solution: Luxxur, a recently launched wheat herbicide that’s also good for tackling wild oats and hard-to-manage perennials. Luxxur’s active ingredients are thiencarbazone-methyl and tribenuron-methyl; both ingredients belong to Group 2.
“Together, this combination has a real good impact on narrow-leaved hawk’s-beard,” said Cranston. “It’s not a single, stand-alone chemical. It’s supposed to be tank mixed with another one.”
“That’s Bayer’s best chemical option,” said Cranston. “I still think also taking the holistic approach.”
Where bad infestations are found, harrowing might also provide a solution, since the weed is surface germinating, said Cranston. “But it’s pretty tough to convince people to do anything with soil in the southwest just because we’ve spent so many years building the soil profile to no till or minimum till that they don’t want to throw it away.”
In order to prevent problems with herbicide carryover or exceeding MRLs, producers do need to be careful that they’re not doubling up on active ingredients in the same year, Brenzil warned. He suggests reviewing Saskatchewan’s Guide To Crop Protection, which is available online and in print from Regional Offices or retail outlets.
It should be noted that there are records of Group 2 resistance in narrow-leaved hawk’s beard in Alberta, and although there are currently none on record in Saskatchewan, resistance is possible. “In that situation, products like Luxxur wouldn’t have any effect,” Brenzil added.
Again, a holistic approach is best. If you think you’ve got narrow-leaved hawk’s-beard in the field, but you’re not sure, be sure contact your regional crop specialist or agronomist.