Early weed control in canola results in yield advantages at no extra cost to producers.
Canola Council of Canada agronomist Kristen Phillips said canola typically emerges within seven to 10 days and gains a leaf every five to seven days.
“Spraying before that two-to-three-leaf stage gives you the biggest yield benefit,” she said.
“Once you spray in that four-to six-leaf stage it’s more of a cosmetic spray and some of your yield has already been lost.”
Even with rainy, cooler weather there should be time to hit that critical stage.
“It’s not going to go from the one-to-four-leaf stage in three days, so you’re going to have still that week of window for ideal crop spraying.”
Most of the canola on the Prairies is now in the ground and emerging.
Phillips said there is a higher chance of yield reduction the longer producers have to wait to spray, but most will switch to aerial application if they can’t get into the fields.
Canola council research has shown yield advantage of three bushels per acre when controlling weeds at the one-to-two-leaf stage compared to the three and four-leaf stage. When compared to the six-to-seven-leaf stage, the advantage is seven bushels per acre. With canola prices around $12, that represents profit of $36 to $84 per acre.
Each herbicide tolerant canola system has its own options.
The window for spraying Roundup Ready varieties with glyphosate is any time from seeding to the six-leaf stage.
Applying it after this point could cause yield loss. A mix with Lontrel can be used to control thistles, buckwheat and large dandelions after the two-leaf stage.
Low drift, or coarse droplet, sprays might not provide enough droplets per square inch because of the low water volumes used with glyphosate.
The canola council recommends producers make sure they use enough water volume to make sure even the smallest weeds are covered. Water volume of five to 10 gallons per acre is preferred.
For LibertyLink varieties, the spraying window is emergence to early bolting, and the rate is based on weed species and pressure.
Liberty should not be mixed with Lontrel for thistle control. If thistles are a problem, Lontrel can be applied before the Liberty or after the thistles have recovered from the Liberty application.
The Canola Council said research at the Agriculture Canada station at Lacombe, Alta., found that just 10 Canada thistle plants per square metre can cause a 10 percent yield loss in canola.
Liberty should be applied as medium to slightly coarse droplets and with water volume of at least 10 gallons per acre. It relies on contact activity and poor coverage from not enough water volume can cause problems.
The window for Clearfield canola varieties is the two-to-six-leaf stages. There are several options for products and tank mixes and producers should check their provincial guides to crop protection for more information.
Kochia control in Clearfield canola is difficult. More than 90 percent of kochia is now resistant to Group 2 herbicides and there are no mixes with herbicides for Clearfield canola that will control the weed.
The Group 2 products used in the Clearfield system usually work well when applied as a coarse spray. Conditions should be warm to ensure good control.
Phillips added that a second pass of weed control is often not worth the cost of the chemical.
“If you have a late flush of a grassy weed, you may not need to control it because it’s going to be outcompeted by the canola, because it’s already cabbaged over and it’s not going to produce seed anyway,” she said.