Weed Management In Wet Weather

Because of the cold and wet conditions, many acres in the province remain unseeded and have not received a pre-seed burnoff herbicide. The weeds continue to grow and are reaching the stage where the herbicide efficacy may become compromised.

Here are a few things to consider with late weed control scenarios.


For a majority of farmers, the first option is still to get the crop planted. However, if the fields are still wet and a pre-seed burn-off application is possible, a tank mix of glyphosate (Roundup WeatherMax) + Heat herbicide can get rid of the weeds that are already up. This tank mix provides faster burnoff compared to glyphosate alone. Please refer to the label of Heat for the restriction on crops to be planted after application.

If the weeds are too big, one option is to apply a higher rate of glyphosate, especially for winter annuals and perennial control.

For pre-seed control, there are several pre-seed tank-mix options available. Applying a tank mix of glyphosate and another registered herbicide may help to achieve maximum efficacy and efficiency. Please refer to theGuide to Crop Protection 2011,from MAFRI, for the different tank-mix combinations in different crops.


For Roundup Ready (RR) crops, tank mixes with glyphosate can be valuable to control tougher weed species. For example, in RR canola you can use Lontrel, in RR soybeans Assure II, Venture L, or Pursuit can be tank mixed and in RR corn, Atrazine, 2,4-D or Dyvel Dsp can be added.

Use caution with choices in corn. 2,4-D applications to corn may result in serious injury to some corn hybrids. Consult your seed representative for varietal tolerance to 2,4-D applications. Apply prior to 4 leaf stage of corn.

In recently seeded crops, be especially cautious. Careful selection of a pre-emergence or early post-emergence herbicide is necessary. Using a non-selective herbicide (as as burn-off ) just before emergence can cause injury.


Make sure to add the necessary adjuvants or surfactants in the spray solution for better burn-off control.

If there is a chance of rain, remember to check the rainfast period of the herbicide. Most herbicides require a rain-free period of at least two to four hours or more.

Do not use a nitrogen fertilizer as a herbicide carrier, as it may increase the chances of crop injury.

Because of the cool weather, the weeds may be growing slowly, and the activity of the herbicides may be even slower. But please be calm and have patience.

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