Hi I'm Damon Smith, Extension field crops
pathologist for the University
Wisconsin-Madison. Today I'm standing
here in a silage trial which is a small
plot trial where we've been testing
fungicides for their effects on reducing
mycotoxins in silage. This particular
hybrid is a BMR hybrid, or a brown midrib
hybrid, specifically developed for the
silage industry. We've been testing
various fungicide products, and also
application timings, over the last couple of seasons
to better understand how they might be
applied to reduce mycotoxins. As you can
see we've got a pretty significant
blighting epidemic here on the leaves.
We've had gray leaf spot, northern corn
leaf blight, and also tar spot, effect
this particular trial and now we also
have ear rots moving in which could be
causing or contributing to some of the
mycotoxin problems that we've seen in
some of these hybrids. Now over the last
few seasons like I said we've been
looking at reducing mycotoxins using
these fungicide applications. What we
have found is that applications
that are centered on the silking window, in
other words from when we have white silk
to brown silk, actually do a really good
job of reducing mycotoxin level
specifically vomitoxin which is usually
a result of excessive gibberellic ear
rot infection in these particular
hybrids. Now we can even hone in better
and get that timing down to actually
looking at white silk to about 10 days
after white silk as the prime window. We
maximize our benefits during that time.
If we go earlier than that white silk
growth stage or later than about 10 days
after that white silk then we often
don't see the level of efficacy against
controlling vomitoxin specifically in
these particular trials one thing to
note in terms of actual product choice
we tend to see products which contain
strobe you learns maybe not giving us is
quite the level of reduction that we
sometimes see out other products which
have higher levels of trials or tries
all specific this is not unlike the
situation in Fusarium head blight with
wheat where we tend to see strobe
eulerian containing products actually
increasing vomitoxin levels there so
it's something to consider as you make a
product choice here in silage corn
production so why do silking
applications of fungicides seem to
maximize the reduction of vomitoxin
well we think it has something to do
with the disease cycle of jibrell ear
rot what happens in the field is that
gibberellin ear rot infects the corn
plant actually through these these silks
or through the white silk channels
during that are one growth stage the
spores are wind dispersed and rain
splash from residue from the last corn
crop and then are distributed up into
those white silks during the season the
fungus then grows down the silks into
that kernel here and we start to get the
rot that you're seeing here so by
applying the fungicides during that silk
timing we believe that that fungicide
application is actually protecting those
silks from fungal invasion here we've
got a set of ears which are displaying
gibberellic ear rot symptoms you can
actually see there's that there's thick
white mycelium or fungal Matt growing in
between these particular kernels this is
something that you want to look for as
you scout for jibrail ear rot in a field
to make decisions on whether you're
going to chop a particular field or not
as symptoms increase it'll oftentimes be
more apparent as as the kernels will
start to take on a red or pinkish
appearance along with that fungal mat
which will also become pink as well and
if they progress more to a pretty severe
type symptom here you can readily see
the red appearance on those particular
kernels and the thick white mat this is
very diagnostic for jibrell ear rot
again will lead to higher vomitoxin
levels often times and silage corn
situations so as you make preparations
to chop your silage fields be sure to
get out in scout fields for symptoms
like we see here on these ears it's
important to determine how significant
the situation is in a particular field
as you're going to want to get these
fields chopped first
also note that it's important to test
for these micro toxins such as vomitoxin
by simply seeing the level of damage
doesn't tell you how much vomitoxin is
actually there you will actually need to
send off a sample to a diagnostic lab to
get the actual levels of vomitoxin in
that feed in a 3646 a publication from
the university wisconsin extension we
include a table 2-16 which has a list of
certified diagnostic labs for more
information about mycotoxins or silage
corn diseases feel free to visit badger
crop
calm or contact your local Extension
agent
you