The appearance this spring of some uncommon weeds is likely due to a lack of spraying last fall, says one weed expert.
Rick Holm from the University of Saskatchewan said fall spraying of 2,4-D would normally take out the two winter annuals spotted in direct-seeded fields earlier this year.
The Canola Council of Canada reported that wood whitlow grass was found in areas of eastern and southern Saskatchewan and pygmyflower was seen in parts of Alberta.
“There were small pockets,” Holm said.
“They’re fairly insignificant. They’re not a huge problem.”
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Winter annuals germinate in the fall, then overwinter and produce flowers and seed in the spring. They usually complete their life cycle by June 1.
Often, they are caught by a fall herbicide application. But the wet fall of 2002 meant many farmers didn’t spray.
Wood whitlow grass is small and produces yellow flowers. It likes light sandy, medium loamy or heavy clay soils and prefers moist soil.
Pygmyflower grows in a small circular mound of leaves with few flowering stems. It prefers dry, open areas and is most often noticed in the spring in forage crops or undisturbed stubble.
Holm said because both plants are small, they are not competitive and unlikely to pose problems.
American dragonhead is another uncommon weed found this year in northeastern Saskatchewan, although it is often confused with other weeds.
It has branched, square, erect stems, with coarsely toothed leaves opposite each other. The flowers are dense spikes of bluish purple. Stiff, spiny bracts at the base of the spike make the head look prickly. It can be confused with hempnettle.
Holm said dragonhead can be found in alfalfa fields. The seed is difficult to separate from forage seed and is spread when new forages are planted.
“It thrives where there is little soil disturbance.”
These weeds generally haven’t caught the attention of herbicide manufacturers so control options are limited.
“With 80 percent of the canola now herbicide tolerant, I’m guessing all of the herbicides involved would control those two,” Holm said of wood whitlow grass and pygmyflower.
The four MCPA formulations may work on American dragonhead, but it is difficult to control, especially in forages.
