(intro music)
Good afternoon, my name is Vince Davis.
I’m the annual cropping systems weed science Extension specialist at the University of
Wisconsin–Madison.
This afternoon, we’re out here, it’s early July–it’s actually July 11, 2012–and
we’ve been experiencing extremely dry conditions rated at moderate drought in our area for
southern Wisconsin this year.
It has been an interesting year from that standpoint to see the visual symptomology
from crop stress due to a lack of early season weed control or weed competition, if you will.
We’ve had less than 2 inches of rain up to this July time period and we experienced
three tenths of an inch of rain for the entire month of June.
What I’m standing in is a visual effect of soybeans where we start out in a system
that had a pre-emergent herbicide and good early season weed control and timely post-emergence
applications.
You can see these beans standing in here are developing quite nicely.
They’re at about the R2 growth stage, they are stressed a little bit for water and moisture
obviously and it would be nice if they were a little bit fuller and closer to canopy,
but there’s very little weeds in here, competing for moisture.
The way these plots were set up as we move throughout the rest of this presentation,
and as you can see across these fields, you can see this crop stress response increases
as you get further away from the camera, but we’ll walk over there in a minute.
The difference has been the aggressiveness of early season weed competition and also
the timing of post-emergence application has been delayed as you see that crop stress increases
as we move across there.
So, here we are as I’ve moved across and here is a system now that experienced later
applications of post-emergence herbicides, and in this year where droughty conditions
have been prevalent, relying on post-emergence herbicides has made control of some weed species,
particularly common lambsquarters, very difficult, where even glyphosate, which usually has good
efficacy, has struggled with common lambsquarters quite a bit with these droughty conditions.
And, you can see here that the soybeans where we have some common lambsquarters escapes
still persisting is that these here, although still look somewhat similar to what we’re
in weed free is still showing more stress and much more visible stress, and it will
be interesting to see how this comes out from a yield reduction standpoint.
Here we are where we’ve moved on across to where we relied on basically a very late
glyphosate application.
You can see the lambsquarters were very tall at the time of application and again the efficacy
was very poor and highly variable.
This, not only, is going to dramatically decrease yield–and that is clearly visible by the
amount of stunting on these soybeans and the high level of stress that is occurring because
these weeds are being so competitive, and in this year particularly for water resources–but
in addition to the yield and crops to stress problems with this system is it’s also a
very poor glyphosate resistance management strategy if the post-emergence management
strategies for lambsquarters control was to rely solely on glyphosate and it usually is
with this weed problem from a post-emergence standpoint because a lack of other non-glyphosate
options is going to be efficacious waiting too late for post-emergence glyphosate timing,
like was done in this particular field.
In comparison, you can see the heavy lambsquarter pressure we had at this location and the extreme
stress the soybeans, if you can see the soybeans in this weedy mess, are under in this situation
where the application has not been applied.
Okay, I’m over in front of our corn plots which are set up the same way I just walked
you through the soybean plots, and that is, where we started out with good pre-emergence
herbicide weed control and strove for weed free conditions.
You can see this corn is starting to roll a little bit, and there is clear visual stress
response in this corn, but in comparison to a lot of growers’ fields around here, this
is pretty normal, and if you look at the efficacy control down in these rows, pretty good control
with only a few minor lambsquarter escapes.
So, I’m going to walk down here, the corn plots, just as I did in the soybean plots,
and I want you to observe the change in corn stress response, as well as corn height reduction
as we walk down.
And, really the difference is the later post-emergence application timing and the decrease in lambsquarters
post-emergence control as you come down, until you get to the point where you see here in
these late, post-emergence application timings where there is extreme crop stress and likely
to be extreme crop yield losses.
And again, we can end up to where you can see the pressures and admittingly, this is
a high level of pressure, both in the soybeans and in the corn I’ve talked about today.
But, these are annual weed species that can be very competitive, and in a year like this
where water competition is important, is very visual.
I’m back here, and we’ve moved to a different part of the farm into a block that is actually
a no-till block we have here.
In Wisconsin, our number one weed problem in no-till is dandelion.
Dandelion is a weed that is highly competitive with water because of its effective perennial
simple taproot it has, it can really absorb water out of the root profile much more effectively
than our annual crops.
Where I’m standing in this corn, again was mid-May planted corn, but this corn that I’m
standing in, although it looks severely stressed, is planted in a plot where there was a fall
herbicide application to mostly control the dandelion.
The dandelion control is not perfect, but it was good enough for this crop to actually
get established.
Now, what’s quite interesting, although you might say that this does not look very
good and you would be correct, is that at the same planting date where the dandelions
were thick and uncontrolled has basically been total crop failure.
So, the carcasses that are left here were planted in this row at the same timing that
this is planted.
As you pan behind me, you can see the remnants in our study where fall applications versus
no fall applications were applied to control the dandelion.
Now again, admittingly, the dandelion pressure in our block because we use this for herbicide
efficacy studies to develop our efficacy tables in our pest management guide, A3646, is maybe
a heavier density of dandelion than most growers would observe, or at least I hope it’s a
heavier dandelion density than most growers would observe.
But, it does show you that extreme and total crop failure can occur when this population
gets out of control.
Okay, to summarize what I’ve talked about so far today, is that I didn’t give great
specifics on weed control removal timing, nor did I give great specifics on herbicide
recommendations, or what to do with this, but I wanted to point the importance of weed
management in years, and particularly stressful years that we have encountered this year,
we started with basically good systems where weeds were adequately controlled and progressed
all the way to where I ended up here with total crop failure because of weed management.
What I want to recommend in a year like this is, this may be an excellent year to get out
there, to scout your fields for weed densities and weed pressures, and do it in the afternoon
and see how that relates to visual crop stress or lack of moisture.
Even in areas where you don’t see visual crop stress, having those detailed scouting
report maps of weed species and weed densities may help you understand the variability in
yield monitor maps at the end of the season and help you evaluate the control strategies
of successes or failures of your weed management program which in a year like this is obviously
very critical.
(exit music)