GOSHEN, Ind. — This is the time of year you can evaluate your fields for weed escapes. It is especially easy to see weeds poking up above the soybean canopy. Escaped waterhemp, giant ragweed, pigweed, horse weed (aka marestail) and even volunteer corn are easy to spot in beans.
Herbicide options are limited this time of the year, primarily to ditch banks, field borders, roadsides and areas that might have drowned out this spring. It may seem a folly to spend time spraying or mowing those areas, but the seeds those weeds produce will be in the soil for a long time. The old saying “one year of weeds means seven years of seeds” comes to mind.
It is a good idea to carry a notebook and sketch a map of the areas that need more attention next year. As large as farms are these days, the maps are a nice way to jog your memory when planning for the 2021 season. This year, I have noticed quite a few fields with strips of weeds near the property lines. No doubt these strips are the result of farmers trying to avoid drift onto the neighbor’s property.
Questions to ask yourself: Did weeds escape because they are resistant to the herbicides used? Was it due to poor coverage? Did the seeds get spread in a swath behind the combine? If there is a lot of volunteer corn in the field, did the corn pass through the combine, or was it the result of some downed corn or stalk rots?
It is becoming clear that herbicides alone (either existing or new chemistry) will not provide us all the answers to our weed management issues. Selecting herbicides with different modes of action, understanding weed biology and how seeds move from location to location, and using mechanical methods to control weeds all are part of the toolbox to keep the weeds at bay.
— Jeff Burbrink, Extension Educator, Purdue Extension Elkhart County
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