Spray weeds early in crop

May 24, 2012 - Issue 13

It only takes 10 Canada thistle shoots per square metre to cause a 10% yield loss in canola.

 

With good soil moisture and heat in the forecast, growing conditions are very good for the crop — and for weeds.

Early weed control reduces weed competition for nutrients and moisture, and improves yield potential for canola. In-crop weed control should occur as early as possible since canola is much more vulnerable to weed competition prior to reaching complete ground cover. Past research has demonstrated an advantage of 3 bu./ac. for controlling weeds at the 1-2 leaf stage of canola versus 3-4 leaf, and a 7 bu./ac. advantage versus 6-7 leaf. At $12 per bushel, that’s $36 to $84 per acre more profit with no added cost.

Scout fields to determine the number, size and species of that are present in each field before choosing a rate and tank mix. Here are the options for each herbicide tolerance system:

Roundup Ready (glyphosate tolerant): The window is from seeding to the 6-leaf stage of the canola crop. Maximum use rates are 270 g ae per acre on one application or two applications of 180 g ae/acre each. You can also tank mix glyphosate with Lontrel 360 at the 112 mL/acre rate when going after thistles, buckwheat, and large dandelions.

Liberty Link (glufosinate tolerant): The window is from cotyledon to early bolting. Set the rate based on weed pressure. Split application is an option, but the maximum allowable rate per season is 2.97 litres per acre. Liberty may be tank mixed with clethodim at 25.5 mL/acre (check crop protection guide for product options) for additional control of grassy weeds. The mixing order is unique when tank mixing clethodim with Liberty. Add the surfactant first, then Liberty, then clethodim. This is one of the only times when surfactant goes in the tank first.

No Lontrel tank mix for Liberty. If using Lontrel for thistle control in Liberty Link canola, it should be applied on its own as a separate, either before the Liberty application or after the thistles recover following the Liberty application. For acceptable control, Canada thistle should have ample leaf area in a living condition for contact and uptake. Remember that Canada thistle is 3 to 4 times more competitive per plant than wild oats. Research from AAFC in Lacombe, Alta., shows it only takes 10 Canada thistle shoots per square metre to cause 10% yield loss in canola. For more on this, read the Canola Council of Canada factsheet, “How many weeds are too many?”

Clearfield (IMI tolerant): The window is from the 2-leaf to the 6-leaf stages. You have a few different products to choose from with several different tank mix partners. Click the link below to see your provincial guide to crop protection. Odyssey, Odyssey DLX, Absolute, Solo or Tensile can be applied only once per season (no split applications), but Odyssey has some residual soil activity. If thistles are a target, Absolute is a co-pack of Odyssey and a dry Lontrel component, or Odyssey itself may be mixed with Lontrel at 0.17 to 0.23 L/acre. Tensile is a co-pack of Solo and the dry Lontrel formulation.

Note that 90% or more of kochia populations are resistant to Group 2 herbicides and there are no mixes with herbicides for Clearfield canola that will control kochia. There may also be rotational crop restrictions following the use of Clearfield herbicides.

Always consult your guide to crop protection and/or product labels for recommended rates, staging, and tank mix partners prior to herbicide applications. Click your province for a link to your guide to crop protection: Alberta Saskatchewan Manitoba.

This chart will help you select the correct glyphosate rate for each formulation and acid equivalent (ae) per acre.

Canola Watch