To improve glyphosate performance, apply…
—When temperatures are greater than 10°C, with the expectation that daytime highs will increase to greater than 15°C
—When nighttime lows are greater than 5°C (the warmer the better up to 10°C)
—Under bright sunshine (thin or sporadic clouds are also OK). Applications made in darkness or heavy cloud are less effective.
—Using water with low levels of hard water ions (Ca and Mg), iron, or suspended clay or organic matter.
—At water volumes of 5-10 gallons/acre.
—When weeds are smaller, ideally at the 1-3 leaf stage.
—At speeds that minimize dusty conditions. Dust on leaves reduces herbicide uptake. If dust cannot be avoided, spray from downwind to upwind to minimize the dust deposition on unsprayed leaves.
Growers have asked in the past if it’s OK to apply glyphosate earlier than the 1-3 leaf stage on Roundup Ready canola? The answer is yes — unless the crop and the weeds are under stress. In that case, hold off until conditions improve for better weed control and to avoid stalling the crop.
The following table, from the Alberta Reduced Tillages website, provides more detail. Click here to download a PDF version if you have trouble reading the table.