By Graham McLean, CCA-ON, CCA, 4R NM

Crop Sales Specialist, AGRIS Co-operative Ltd.

Prior to soybean harvest and certainly after harvest the weed escapes are obvious. Some fields required a preharvest burndown just to facilitate harvest and reduce the risk of dirt tagging especially on IP soybeans. I know a lot of bean fields were sprayed late often with only one spray pass and likely without any residual chemistry applied. This has resulted in late season weed escapes.

Take a look at the weed spectrum you have in each field. This will help decide on a control strategy. There is lots of late emerging fleabane, chickweed, winter perennials and biennials still growing.

We have an opportunity this fall to control some of these weeds and prevent further seed set or take out the smaller weeds that have germinated.

An application of herbicides in the fall ahead of wheat or prior to fall tillage allows us to use alternative modes of action and get a head start on next years weed control options.

Glyphosate resistant weeds remain an issue. A late spring and soggy field conditions understandably delayed control. By the time we did get into the fields the weeds were large and control was variable. This has added to the seed weed bank for future years. A comprehensive weed control strategy will be needed for the following year(s) to regain the upper hand on control of these tough resistant weeds

Fall application has advantages in controlling perennials and biennials. The plants are trans-locating sugars to the roots in the fall which also carries the herbicide to the growing points in the roots. Picture below showing the dandelions in the soybeans.

Photo above shows dead wild carrot and new actively growing plants.

A lot of wild carrot (above pic) showed up this spring often times in strips. This is likely caused by a few plants put through the combine in previous years that spread the weeds seeds in a wider swath. This issue has been several years in the making. This spring the late application on large weeds offered variable control. Wild carrot is one plant we can control with appropriate product choices I doubt it is resistant at least not yet but we cannot rule out different biotypes.

Burning down clovers and alfalfa fields is easier in the fall, dicamba and glyphosate tank mix is my number one treatment. We could use 2,4-D and glyphosate, but I recommend keeping the glyphosate at 1 l/ac. We have many choices to choose from in both dicamba and 2,4-D products. Keep in mind the growth regulators take longer to die down, but they do a better job of cleaning up the fields especially the biennials and perennials.

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