“A lot of canola seed, in a lot of canola fields, hit the ground.”
– BrUce mUrraY
Farmers who grew canola last year can expect a lot more canola volunteers than usual in their fields this spring, says Manitoba Agriculture, Food and Rural Initiatives’ (MAFRI) weed specialist Bruce Murray.
Since canola volunteers are easier to kill when young, and it takes more planning if they are Roundup Ready, farmers should be scouting their fields early before spring seeding.
Most years a lot of canola seed hits the ground due to shattering in the swath, during harvesting or through the back of the combine. The latter is due to improper machine adjustments or travelling too fast. But in 2008 strong winds and heavy rains, especially in the Red River Valley and the east, shattered more seed pods than normal, Murray told farmers attending Ag Days.
What’s normal? In 1999 and 2000 weed scientists Robert Gulden sampled 35 canola fields after harvest that had not grown canola in the previous four years. The fields averaged around 35 bushels an acre, but Gulden found close to two bushels an acre of seed on the ground.
“That’s about 20 times the (canola) seeding rate (of five pounds or 0.1 bushels an acre),” Murray said. “I bet you it’s double that (in 2008). A lot of canola seed, in a lot of canola fields, hit the ground.”
But even in “normal” years it looks like farmers drop three to 10 per cent of their canola yield on the ground. Fortunately, some of those seeds germinate in fall and freeze to death. Some seeds are destroyed other ways.
Most of the seed germinates the following year, unless they have become dormant and been buried four or five inches, in which case, they can pop up several years later, Murray said.
Canola volunteers are a lot easier to control when herbicides are applied at the two-to three-leaf stage than at the five to six.
“If you had canola, walk those fields,” Murray said. “And plan your rotation. If you had Roundup Ready and you’ve got Roundup Ready stuff showing up, don’t put a conventional sunflower in there, or conventional soybean, because it’s going to be tough (to control the Roundup Ready volunteers in crop). I don’t have any miracles. That’s a hard conversation to have – telling a guy ‘you’re done.’”
Murray also warned farmers to be careful applying 2,4-D as
a pre-emergent control because the residue can hurt certain newly emerging crops like sunflowers.
There are registered herbicides for controlling canola before seeding cereals, corns, pulses, canary seed and forage grasses and can be found in MAFRI’s Guide to Field Crop Protection.
One is CleanStart – a combination of glyphosate and carfentrazone. It works best when the canola volunteers are small.
“They really mean it when they say apply at the two-to three-leaf stage,” Murray said. “If you go beyond that your control really drops off. It’s a good option.”
CleanStart doesn’t leave any residue so it’s safe to plant a wide array of crops after using, Murray said.
Those crops include barley, mustard, dry beans, oats, canola, field peas, chickpea, rye, corn sunflower, flax triticale, lentil and wheat.
“It is contact herbicide, so when you spray it, it needs to be warm, which is a little tough sometimes in the spring.” [email protected]