There has been no change at the top of the Top 10 list of weeds in Saskatchewan but plenty of movement at the bottom.
Green foxtail gets top billing, followed by wild oats and wild buckwheat. They have held those positions since Agriculture Canada began the survey in the 1970s.
The most recent survey was conducted in 2,242 fields in late summer of 2014 and 2015 following in-crop management.
The survey is conducted every 10 years or so, and the last one was in 2003. That was a dry year, as was 2015, but 2014 was a wet year.
The fields are randomly selected and proportionally allocated to the target crops of canola, wheat, durum, barley, peas, lentils, oats, flax and mustard.
Weeds are counted in 20 sq. metre quadrants and ranked based on frequency (percentage of fields containing the weed), uniformity (percentage of quadrants in each field infested with the weed) and density (the number of weeds per sq. metre). Each factor is given equal weighting in the ranking.
Volunteer canola is No. 4 on the 2014-15 list, up 10 spots from 2003.
That is no surprise to Julia Leeson, a weed monitoring biologist with Agriculture Canada who compiled the list, because canola acres nearly doubled in the province between 2003 and 2015.
Canola bumped Canada thistle down one spot to No. 5.
“The interesting one is spiny annual sow-thistle,” she said.
“That’s No. 6, and that came up a long way.”
It vaulted a surprising 28 spots from the 2003 list.
“The amount that it increased to make it into the Top 10 is quite dramatic in my opinion, and I think we need to nail down why it is that it increased,” said Leeson.
Conditions were ideal for spiny annual sow-thistle in 2014 because the weed thrives under moist conditions. It is a late germinating weed that can avoid herbicide applications and has some herbicide resistance capability.
Leeson also thinks it is possible the weed may have been under-estimated in previous surveys.
“It’s a species that I don’t think everybody is familiar with,” she said.
“People might assume it is perennial sow thistle, so there could be some identification issues. People don’t know what they have.”
Next on the list is cleavers, which has been steadily increasing as it extends its reach across the province.
“It used to be up in the north, and it is slowly moving down,” Leeson said.
“It follows canola production.”.
Lamb’s-quarters fell three spots to No. 8.
“It is a common weed,” she said.
“It has always been there. It is down a little bit due to these other things coming up.”
Narrow-leaved hawksbeard was another list climber, jumping 11 spots to take over the No. 9 position as it continues its intrusion into southern Saskatchewan.
“It does well in zero till and everybody is zero till, pretty much,” said Leeson.
Dandelion captured the final spot on the Top 10 list, moving up one spot from 2003.
Stinkweed, volunteer wheat, kochia, redroot pigweed and Russian thistle dropped out of the Top 10.
Russian thistle plummeted 20 spots to No. 30, while redroot pigweed tumbled 16 spots to 23.
Kochia fell seven spots to No. 15, wheat was down four spots to No. 13 and stinkweed dropped five spots to No. 11.
The Agricultural Development Fund, Saskatchewan Pulse Growers and the Western Grains Research Foundation funded the survey.