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Wild oats and green foxtail are growing “like crazy” and rain will bring a flush of broadleaf annuals. In-crop herbicide applications are best done as early as possible.
The first in-crop herbicide opportunity varies by HT system and by tank mix. Glyphosate can go on Roundup Ready canola at basically any time up to the 6-leaf stage. Liberty can go on at emergence of Liberty Link canola. In the Clearfield system, the first application of IMI products can go on at the 2-leaf stage of the crop. Read more on crop staging.
Earlier is better. Research has demonstrated an advantage of 3 bu./ac. for controlling weeds at the 1-2 leaf stage of canola versus the 3-4 leaf stage, and a 7 bu./ac. advantage for the 1-2 leaf stage versus the 6-7 leaf stage.
These numbers will be even higher if a preseed burnoff was not completed. If the crop is seeded without a pre-seed burnoff, in-crop weed control should occur as early as possible. Canola is much more vulnerable to weed competition prior to reaching complete ground cover. Smaller weeds are also much easier to kill than weeds at the 4-leaf stage or later.
Rain has kept sprayers off fields. The longer a herbicide sits in a sprayer, the greater the risk that it is going to hang up in the tank. Sprayers should be cleaned at the end of every work day regardless if the same product or tank mix is being sprayed the following day.
Further reading:
Cleaning out the sprayer — tips
Grassy weed control in HT canola crops
When would a second in-crop application make sense?
Rainfastness: Spraying before a rain
Tips for spraying in the wind
Sprayers 101: Top sprayer retrofits
