Are You PRE-pared for the Soybean (and Waterhemp) Growing Season?

Rodrigo Werle and Shawn Conley

Spring has arrived rather quickly in Wisconsin and the planting season is right around the corner (or perhaps it has already started for some growers). Before getting their soybeans in the ground, farmers should make sure they have solid weed management plans for the growing season, particularly if waterhemp is present in their operations.

According to our 2018 Survey, several Wisconsin soybean fields get only treated with a one-pass POST-emergence herbicide program (keep in mind that pre-plant tillage is a common practice adopted in Wisconsin cropping systems and that helps farmers “start clean”). Because of the widespread occurrence of waterhemp populations resistant to glyphosate and/or other POST-emergence herbicides (e.g., ALS- and PPO-inhibitors; see article: Herbicide Resistance in Wisconsin: An Overview”) combined with its extended emergence window (mid-May through July), a one-pass POST-emergence program in soybeans is likely not a viable strategy in fields infested with waterhemp.

Moreover, research conducted across the Midwest has demonstrated the importance of keeping the soybean crop weed-free from establishment through the V3 growth stage (3rd trifoliate). Weeds emerging after the V3 growth stage will likely not impact soybean yield; however, they should still be proactively managed to prevent them from reproducing and replenishing the seedbank (remember “no seed, no weed”). Thus, effective PRE-emergence herbicides can help farmers maintain their fields weed-free during initial establishment of the crop (= achieve full yield potential) and also reduce the selection pressure on POST-emergence herbicides (due to fewer weeds to be controlled POST-emergence), helping on the fight against herbicide resistance. (Continue Reading)

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