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Soybean Seedling Injury Symptoms

My name is Bill Johnson I’m an extension weed scientist at
Purdue University and I’m Kirsten Wise I’m the extension specialist for field crop
diseases at Purdue University and we’re here today in Indiana soybean
field to talk about soybean seedlings that are showing injury symptoms. Farmers that were lucky
enough to plant at the end of April may be
experiencing some symptoms of injury on their soybeans. One of the
things that we know causes injury is a phytotoxic effect that occurs
from the new fungicide fluopyram. This fungicide is marketed as
ILeVO by Bayer Crop Sciences and it’s promoted
to reduce the symptoms of sudden death
syndrome or SDS. Now Purdue research and research across the midwest shown that
this fungicide can be effective in reducing the symptoms later on in the
season however growers may be concerned about some of the injury symptoms
they’re seeing right now. Just as a demonstration some of they
symptoms that you’ll see with the halo effect are going to be a browning or
discoloration on the cotyledon, you’ll see kind of a in the cool wet conditions may be able
to even be almost a blackish color usually along the outer edges of the
cotyledon Now although we see this effect it can be more severe under these
cool, wet conditions so areas of the field that may have experienced poor drainage,
compaction, ponding all of those symptoms will be more
pronounced in those areas. Another thing that we’re seeing is that fields that would have an application a
pre-emergence herbicide and were planted with seed that were
treated with ILeVO may experience more severe symptoms. In 2014 a vast majority of the beans in
western Indiana were planted over about a three or four day period. Seven to 10 days after that we had wet
conditions followed by a couple nights of frost, as a
result I got more phone calls on herbicide
injury in a one-week period a time in early June than I’d received over the past 10
years combined. This year we’re starting to get a few
reports of soybean herbicide injury coming into our officers. Now many
soybean varieties are tolerant to the herbicide sulfentrazone. However not all seed companies make this information available to
farmers. Sulfentrazone, or the Authority containing herbicides, are very
valuable herbicides for control of small seaded broadleaf weeds and so they’re very popular for Midwest
soybean production, however they do have injury potential.
Typically when we see injury from sulfentrazone we have a soybean variety that is sensitive to it or we have a situation where the beans are in the crook
stage and a splashing rain is received and sulfentrazone is washed up on the foliage of the plant. Now what I want to show you here is a situation
where we had beans planted about three weeks ago, the beans
did not emerge for about 10 days due to cool conditions, however we did
not have a splashing rainfall event nor do we have a soybean variety that
sensitive to sulfentrazone and so if you take a look at the two rows
on either side to me you notice these rows don’t show injury
symptoms biomass wise they appear to be bigger
than the rows adjacent to these rows. So even though we
had a herbicide with some injury potential,
sprayed under conditions in which we had cool wet soil conditions, we didn’t have
the perfect storm of a sensitive variety and hard
splashing rain occurring with this as well. Although we do see more injury in
the rows that were treated with the ILeVO seed treatment and
received a pre-emergent herbicide application we do know from my past research in 2014 that we won’t see any long-term yield
impact from these results. After a number years of doing this type of
research what we find is if as long as our stand counts are in the
desired range, and usually that’s ninety thousand or
more plants per acre, it doesn’t hurt soybeans to have a
little bit of necrotic tissue on the unifoliates or trifoliates or to be gnarled up a little bit if
they resume natural, normal growth within about 10
days or so. So I think it’s it’s very crucial to
assess your stand when assessing herbicide damage and based on what Kiersten said earlier it appears like the same situation is
true for the ILeVO treated plots in that as long as you’re stand is OK
soybean yield should not be impacted.

Cesar Sullivan

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