Soybean Preemergence Herbicides: Always have one down

Soybean Preemergence Herbicides: Always have one down


We’re looking today at some of our weed
management trials in soybean, a similar but yet different story than what we
evaluated and talked about in the corn weed management trial. Planting dates
around the end of May, May 26th or so, and what we find again is we went into a dry
period where not all of our preemergence products were activated
quick enough to get complete control or control of some of our really tough
weeds like, giant ragweed. They were successful in controlling some of our
small seeded weeds, like lambsquarters waterhemp, and some of the grasses, but we
certainly saw misses in our giant ragweed. Some differences: When we compare
into the corn weed management, we spoke a lot about reach back. Once we have the
rainfall, we get reach back we see some of those herbicide chemistries being
able to take down weeds that are already emerged. We don’t have quite that same
flexibility in the soybeans. Those herbicides don’t have the reach back, but
they do have what I would call “reach forward.” We put them on for the residual
activity. We want them to continue to work for us during the growing season
and that’s what we see now. Here are some comparisons: If we did not use the
preemergence herbicides, we were looking at putting our first early POST
four days after those beans emerged. We planted on the 26th, they emerged on June
5th, but by June 9th, we needed to get that postemergence on to take those small
weeds out and small matchbook sized weeds, like giant ragweed, lambsquarters,
waterhemp. We needed to be there to have successful
control. With our preemergence that were successful, it still bought us about
three to four weeks time before we needed to put our POST and our best
performers, we’re still waiting. We will have maybe
four, five weeks before we need to put that postemergence control on. In summary again, let’s review why it’s so important to use that pre-emergence
product in our soybeans. First, it does reduce the density of certain weed
species and in many cases takes out the complete flush of other weeds, like our
small seeded broadleaves, so it’s helping you there. It opens that window of
time that you need to get your postemergence program on. It may be different
each year. You need to scout your field and watch for how those weeds are coming
through, because of the rainfall and when products are activated, but it may buy
you two three four weeks of time before you need to come back with that postemergence program. So you decrease the density, you decrease the number of
species and it does buy you needed time during the summer spraying. So one last
reminder, folks, always ask was it worth putting that preemergence on. Well, if
you have a skip in your field, you can see it. It is always worth that. It does
maybe not reach back, but we look at reaching forward to continue to control
weeds with those residual products through that growing season.