- Devin Hammer.
Devin is a graduate student
under Doctor Conley and Doctor Stoltenberg.
Devin is researching how selecting for genetic gain
in soybean breeding has affected its competitive ability
with weeds and how combinations
of multiple management strategies impact pigweed emergence
and persistence in soybean production.
He also runs herbicide dose response trials
in a greenhouse to test potential
herbicide resistant populations collected here in Wisconsin.
He received his BS at University of Illinois
and is working on his Master's.
With that, please help me welcome Devin Hammer.
(audience applauses)
- Well, thanks for the introduction, Jeff.
I was told I was the first talk this morning,
so I would have to work out the bugs myself
and wouldn't be able to blame anybody.
So without further ado, the talk is
about herbicide resistant update in Wisconsin,
but I kind of wanted to flesh that out a little bit
and not only talk about progression of resistance
over the last five years, and I want to focus mainly
on horseweed or marestail, giant ragweed,
common ragweed, waterhemp, and Palmer amaranth.
Then, I want to go into, kind of shift gears
and teach how to identify these pigweed species,
focusing mainly on the redroot pigweed,
the waterhemp, and the Palmer
'cause those can be kind of tricky.
And then, I want to jump in how we do
our herbicide screening in the greenhouse,
how we run our dose response, and I want to talk
about some current research, as well.
So right off the bat, this is gonna be
a continuing template kind of for the next few slides,
so I want to break it down.
At the top, you'll see we've got the United States breakdown
so that number of states we have resistant numbers
of weeds, horseweed, in the country.
The number of sites of action, and this could be resistance
to glyphosate, PPO inhibitor resistance,
ALS inhibitor resistance, and we also have
the number of cases of multiple resistance,
and that could be a two-way or a three-way,
different modes of action, but what I'm gonna focus on
is keeping in Wisconsin.
So for horseweed, we have known
glyphosate resistant biotypes,
and we've had those since 2012.
And I'm also gonna have these maps which are gonna be
pretty consistent for the next few slides, as well.
So starting in 2012, we had confirmed resistant populations
to glyphosate in Jefferson County, I believe,
and we also tested another county,
but it came back no resistance.
So what I mean by no confirmed resistance
is when we tested it, we tested it in the greenhouse,
and we didn't see anything.
We can't call it susceptible due to some technicalities.
We didn't test it far enough to say it was susceptible.
And you'll also notice there's a box there striped
for suspected resistance, and that just means
that we are testing it currently in the greenhouse,
and we can't confirm anything or deny anything.
So jumping into 2013 to the present,
we also confirmed another county.
Columbia County has a resistant population
for horseweed, as well.
Moving on to giant ragweed, you'll see the breakdown
nationwide is very similar
in some respects to the horseweed.
Focusing on Wisconsin again, you'll see
glyphosate resistant biotypes since 2011,
and we also have had ALS inhibitor resistant
biotypes since 2013.
2011, 2012, we just had the single population
in Rock County resistant to glyphosate.
Moving into 2013 to present, there were
several counties that were tested.
None came back glyphosate resistant, but we did have one
that was ALS inhibitor resistant in Columbia County.
Common ragweed, in Wisconsin, we've known
about ALS inhibitor resistant biotypes since 2013,
a population we collected in Brown County,
as well as a few others.
They didn't come back resistant, however.
Now, moving on to the real bread and butter, I guess,
of my presentation is the one everyone's worried about,
the pigweeds, and I'm gonna start with waterhemp.
One thing I want to point out is if you do look
at the United States statistics there,
the number of states may not be as different
with some of the other weeds, the common ragweed,
the giant ragweed, but you notice the sites of action
that it's resistant to kind of jumps up.
You see a number six, and also the multiple cases
of resistance jumps up to 11.
With the weeds that I've showed you before that,
the ragweeds and the marestail,
those were two-way resistances almost always.
With waterhemp and Palmer, as you'll see,
we're dealing with three-, four-,
and even maybe five-way resistances
across the United States.
Thankfully, we haven't confirmed any in Wisconsin, though,
but we have known about ALS inhibitor resistant biotypes
since the late '90s and also recently confirmed
glyphosate resistant populations, as well.
So starting in 2012, there were a few counties
that were tested, and none came back resistant.
In 2013, we did find resistant populations
in Pierce and Eau Claire County.
And this is about the time that I started to think
about joining grad school, so I always
got the joke, when I came here,
I brought all this resistant pigweed with me.
They always joked that I filled my pockets with the seed
and just kind of sprinkled it as I walked around
out in the fields, but that's not the case at all.
2014, we tested a few more counties.
In Chippewa, we had our first suspected
two-way resistant population
with PPO inhibitors and glyphosate.
Almost done testing those in the greenhouse.
I should have those results out in a month or so,
but for right now, we're still testing.
Now, 2015, this is the really big one.
You'll notice that there was a significant jump
between these two years.
In fact, 18 additional counties reported
concerns of glyphosate or herbicide resistant waterhemp.
Now, I'd like to point out this didn't just happen.
It's not just in one year, (fingers snap)
18 counties all of a sudden had waterhemp
and all of a sudden had issues
killing them with glyphosate.
This is a case where most likely you see
one or two plants surviving in the field,
and you think, "Oh, well, I'll get those next year.
"It's not a big deal."
And then, you harvest, and then, the next year
you have a few more, and you let them go.
And then, all of a sudden, your field's overrun.
So I think that's kind of the case.
People thought one or two plants wasn't a big deal,
but as many seeds as this weed can produce,
it can be a very big issue when you leave
a weed like that out there.
And also, another thing I want to talk about
is you'll see these asterisks over some of these counties.
So those were tested
by the University of Illinois' Plant Clinic.
How they do their testing is they take
whole plant samples, live tissue, and they run
genetic marker assays, and they find markers
that are closely linked with resistant biotypes,
which is a very reliable and robust method.
It's just different from what we do,
which is screening with herbicide in the greenhouse.
So I just wanted to point out the distinction there.
Moving on to Palmer, in Wisconsin,
we have had glyphosate resistant biotypes since 2013.
You'll notice that nationwide, it's very similar
to waterhemp in the number of sites of action,
the number of multiple resistant cases.
So 2013, there was just the lone glyphosate resistant
population in Dane County.
And then last year, or I guess not last year anymore,
2014, we found suspected HPPD and ALS resistant biotype
in Iowa County, which we are also almost done testing.
And just this past year, we confirmed
another resistant population in Sauk County,
and we are investigating a case of Palmer amaranth
in Grant County, as well.
So now, I want to talk a little bit
about how to identify these pigweeds.
So the first thing I want to look at when I see
one of these, I look at the stem
because that's, right off the bat, you can
whittle it down, you can divide this family
of weeds pretty evenly.
So if you look at the one on the left, the picture on the left,
you'll see it has the fine white hairs along the stem
and the petioles, and right away,
you know that's either gonna be a redroot pigweed,
a smooth pigweed, or a Powell amaranth.
Now, if you see one that looks like on the right
where it's just completely smooth,
no hairs at all, that's the ones you might want to start
worrying about when you have waterhemp or Palmer amaranth.
Spiny amaranth also has the smooth stem,
but you'll notice spines right
underneath the leaves, as well.
So that's a dead giveaway for that.
But now, I want to break down Palmer and waterhemps,
since those are the two big ones.
You'll see the pictures of the leaf I have right here.
The one on the left is the waterhemp.
It's got that longer, diamond-shaped leaf,
making the petiole shorter.
You'll notice it kind of tapers off
towards the bottom there.
Now, the Palmer on the right,
I like to call it more egg-shaped.
It kind of rounds off more abruptly,
and it leaves that petiole much longer.
I'm sure a lot of you have seen the pictures
where people bend that leaf over,
and you can see a petiole's much longer with the Palmer.
This picture here is just another representation of that.
I kind of took a bird's-eye view.
You can see the leaves of the waterhemp on the left.
They kind of shade out everything.
You can't see through them, but with the Palmer
there on the right, you can kind of look
from the top, and you can see the ground or whatever below.
It's just another good representation
of the petiole length and the leaf length.
The dead giveaway for me when I look at these,
especially late in the summer, early fall,
is when they put on seeds, when they put on their flowers,
waterhemp, on the right, I like to call more
of a wiry, thin seed head, and we kind of measure it
in terms of inches, three, four,
five, six inches of a seed head.
And you'll notice the Palmer on the right
is basically all seed head once it matures.
We measure it, usually, in terms of feet.
It puts on a lot of seed, and it's much thicker looking
and longer, obviously.
It just looks like a stronger seed head
than the waterhemp, usually kind of wiry and spindly.
Another close-up view here of the female seed heads,
so these are dioecious species,
meaning that they have separate male and female plants.
So the females are the ones that are gonna produce
that seed, and they're the ones you want
to worry about going into the next year
to build up that seed bank.
So when we look at the females,
another thing you want to look at
is the bracts on those seed heads.
So when you feel the waterhemp,
you can run your hands along those,
and it's not gonna do anything.
You're not gonna feel anything, but if you let
that mature female Palmer amaranth plant go,
and you feel that near the end of the year,
and you run your hand along it,
you're probably gonna prick your finger
because they're very, very spiny and very prickly
and can be very painful to handle,
and I've learned that many a time
trying to collect seed to spray in the greenhouse.
So shifting gears again, I just want to talk a little bit
about how we do our herbicide screening
in the greenhouse and give a short example.
So this is our setup.
We have our spray chamber here, and we're getting ready to spray
the Grant County Palmer we actually collected this fall.
And off to the right, there's, off the picture,
a CO2 tank we have hooked up, and you can kind of just see
the nozzle poking out from the top of that door there.
And so, we just spray it once we calibrate it,
pull it out, and we can do it really efficiently
once we get it going and calibrated.
Pull one out, put the next one in, spray it, and go.
So this is just kind of an example of some stuff
I did last year with a Outagamie County population
of waterhemp.
So I have my rates here.
It's just a factor of two, so the one highlighted
is our labeled rate, our one X rate,
and to the left or the right of that,
I have factors of two, so a half to the left,
and doubled to the right,
going all the way up to a 16 X rate.
So how we do, how we measure our results
is we take the shoot biomass 28 days after application,
cut that at the base, and then, we dry it down,
and we analyze the biomass data
using a dose response model package
in our statistical software, and we compare the ED 50s,
the estimated dose to reduce the plant biomass to 50%.
So I'll show you a curve here.
This is comparing the susceptible,
the solid line at the bottom,
to the Outagamie potentially resistant population
at the top, and you'll notice I have
the ED 50s labeled there.
It's very, very different, and it comes out
to roughly a 6 1/2 fold glyphosate resistance.
So all those error bars are each
of those rates that I showed you before,
and I'll kind of flip back to this here in a second.
This is the comparison of the biomass
at each of those rates for both populations,
the significant difference of the two,
and you'll notice the first two weren't
significantly different, but after that,
all of the rates were.
So you notice the lines here, the first two error bars,
they're very close.
They kind of overlap a little bit,
but at that half X, which is that first error bar
where you start to see that big dip,
that's where this susceptible population
really took a hit from the glyphosate,
but you can see the Outagamie County population
just keeps on trucking.
It really doesn't affect it at all,
and you'll notice, even when you get to the 16 X rate,
you're not killing that Outagamie population completely,
or you're not reducing the biomass
nearly as severely, as it's susceptible, as it's flatlining.
So here are just some pictures I took this past summer.
This is some waterhemp just taking over
anywhere it can in between the rows
in this soybean field here.
This is actually the Palmer amaranth
that we found in Grant County in an alfalfa field.
And then, this is just another picture of a,
well, it was a soybean field.
It looks mostly like waterhemp in some of the spots there.
So I guess what I want to get into
is some current research that we're looking at,
other ways to control these weeds or to manage them
other than just relying on herbicides alone.
So one of my research project is what's called
the USB Systems Study, and what I do
is I compare a standard system
we have set up for Wisconsin.
So a no-till, one-pass glyphosate
in the post application, compare that
to other management strategies
combining a pre with the post,
different tillage strategies, so on some of those,
like you can see in the picture on the top here,
I have the moldboard plowing I did, actually,
and then, we come back in the spring,
and I'll till those over to smooth them out before planting.
We also include the use of a cover crop,
and we just combine all of those strategies
to kind of see what works best to control weeds
and focusing primarily on the pigweeds,
and you can see right there in that picture, as well,
I just planted the cover crop this year with rye.
So this is just another picture I took
right at the post application timing.
The one on the left had a pre-application.
You can see it's pretty clean,
and the one on the right did not,
and it's a lot of green there
in between the rows of those soybeans.
So I actually had an inner row cultivation
on this one on the left, and you can see,
it really prolonged the time I needed.
I didn't have to spray that post that time
because the inner row cultivation
really allowed me to give it a little more time
to grow and to shade those weeds out
instead of using a herbicide at that time.
So now, I have some conclusions.
Glyphosate resistant waterhemp is spreading
throughout Wisconsin.
Nine counties are confirmed right now,
and nine more are suspected just this past year
that we're testing in the greenhouse.
This doesn't mean that every plant that you see
in these counties or anywhere is resistant,
but it's something to be mindful of,
and populations can be segregating.
As I mentioned earlier, you can start off
killing most of a population in your field,
and you can leave one or two out there,
but the one or two could very well be resistant,
and you just let that go year after year,
and you're gonna see increasing problems
if you just let that go.
You need to make sure you're being mindful
and manage it well.
Palmer amaranth is also starting to spread.
It's here in Wisconsin.
We have glyphosate resistant populations.
People need to really look out for that one, too.
So what can we do?
So I took these points right off
the Take Action against Herbicide Resistant Weeds website.
So know your weeds.
It's important to know, especially the difference
between the pigweeds.
Are you dealing with a redroot,
or are you dealing with a waterhemp or a Palmer?
Because one can be much more serious than the other.
Manage your fields.
Diversify your weed management strategies.
Make sure your tillage and harvest equipment
is used in those contaminated fields last.
If you know you have herbicide resistant weeds,
make sure you're going through those fields last,
and then, you clean those off after you're done using it
because you don't want to spread that to other fields.
You want to try to minimize the areas where you're dealing
with herbicide resistant weeds.
Understand your herbicides.
Make sure you use a pre.
Very important to use a pre.
It cost a little extra money, but in the long run,
definitely worth it, and you want to make sure
you tank mix multiple modes of action.
It's not good enough just to really rotate modes of action.
It's really important to mix them together
so you're getting the benefit
of the multiple use all in once.
Use the labeled rates.
Use proper adjuvants, and apply correct timings.
Basically, read the labels, whoever's applying
the herbicide, and make sure they're doing it
the right way because that's just as important.
Just a quick thanks to all the help I got
this summer in the field in the greenhouse,
running around collecting waterhemp seed.
I'd also like to thank United Soybean Board
for funding the research.
If you have any other questions
or need some more information,
I highly recommend these websites.
For weed ID especially, the weed tab
at cals.wisc.edu is really helpful.
Also, if you have any other questions
about herbicide resistant management,
I'd recommend the takeactionweeds.com
or the weedscience.org.
Ethan Heap's got a really good website there, as well.
With that, I'll take any questions
if I have a little bit of time.
(audience applauses)