The opportunity to spray weeds is nearly closed for this fall, especially on fields planned for canola in 2012. If you have a stretch of warm sunny days in the forecast, you might have a chance to give dandelions one last hit. Note that glyphosate needs a few warm days with several hours per day of bright sunlight as well as non-freezing conditions (day and night) to do its job well. If using residual product, be mindful what you’re seeding next spring. The best product to use at this time of year is 2,4-D, but spraying now ahead of canola won’t give it enough time to break down before seeding next spring. Do not spray 2,4-D on land planned for canola next spring. 2,4-D is suitable to clean up fields for cereals next year.
2,4-D can be applied for winter annual control as long as the nozzles are not freezing up. If you have the space, keep the sprayer in a heated shop overnight and wait until temperatures are above freezing to start spraying. Phenoxy herbicides not only control winter annuals directly by crushing stem tissues and cutting of water supplies, but also by sending a signal to resume growth when they should be entering a dormancy phase to survive the winter.
If your target is narrow-leaved hawk’s-beard, take note: This weed is not susceptible to 2,4-D at this time of year and 2,4-D can actually interfere with hawk’s -beard control next spring with glyphosate. That’s because the injury that 2,4-D causes to the plant actually protects it from the glyphosate.