Hello folks Rodrigo Werle weed scientist at
UW-Madison, with me I have Felipe Faleco a weed science
graduate student at UW-Madison. And today we're here to talk about the concerning
weed species Palmer Amaranth that's coming into our state via contaminated
seed, grain, feed, and sometimes with equipment. Okay so Palmer Amaranth used
to be a major and driver weed problem in the mid-south and still is is the number
one problematic weed species in the southern US and is creeping in into the
Midwest okay becoming a major concerning problem.
In the state of Wisconsin thus far we have detected this species and nine
different counties, okay last year last growing season 2018 it was my first year
here in Madison as a weed scientist and I had the opportunity to visit two
different fields that were infested with Palmer Amaranth. One of them the
introduction for the Palmer Amaranth seed was believed to be caused by
feeding cotton seeds from the south to dairy cows introduced to the field, and
the second one was through contaminated grain that came to the state from other
states okay. So one of these fields at the end of the year I had the opportunity to
go back and collect seeds. We grew some of those seeds in the greenhouse we then
sent leaf samples to the University of Illinois plant clinic lab for two
reasons to confirm that those plants were actually Palmer Amaranth, and to
test for resistance to glyphosate and PPO herbicides. Results came back and the
population was indeed confirmed to their molecular tests to be Palmer
Amaranth and resistant to glyphosate. After we received those tests back I
challenged my graduate student Felipe to conduct the screening here
that he's gonna describe to us. So here we are working with two populations this
population here is from Western of Nebraska it's a glyphosate susceptible
population, and this one here it's from southern of Wisconsin that we are
testing to compare if we found some resistance to
this population. So we sprayed these populations with eight different
herbicides, glyphosate sand seven more websites that is commonly used in corn
production and soybean production. And we sprayed these populations between two
and a half and four inches following all the label specifications and the
adjuvants. and we sprayed these plants 20 days ago. Alright folks so Felipe just
described the methodology for the study here how we conducted it, and we thought
be important to show and record this video here just because the results are
quite impressive and then not as not good for our production systems okay. So
when I'm walking through the flats here keep in mind that the this population
here is our control glyphosate sensitive from western Nebraska, and this here it's
always going to be the population from southern Wisconsin. As the molecular
results from Illinois indicated this population that we found in Wisconsin
turned out to be resistant to glyphosate we sprayed with the 22 fluid ounces of
Roundup PowerMax and as you can see here the plants are doing just fine,
whereas we got complete control with our population from western Nebraska okay.
The next herbicide that we conducted the molecular task for was PPO or group 14,
okay so we sprayed Cobra here post emergence and these are the plants that
I have. So this population from Nebraska was also sensitive to PPO or did not
have the PPO mutation according to the molecular results. And here is our
population from Wisconsin. We submitted the sample and it came back negative
for that resistance, however when we sprayed the 12.5 fluid ounces of Cobra
as you can see here we could not get a complete kill okay. And that's the one
bit of important consideration when managing Palmer Amaranth and also water hemp.
Post control with PPO herbicide is very difficult one because of resistance
and populations are resistant, but just because of the way this plant growth and
I want to expand that a little bit showing this plant. So this plant here my
students chopped when it was a foot tall okay and as you
can see here this plant is just growing back. So controlling pigweeds with
contact herbicides post emergence can be very difficult. Again if the molecular
results indicate you don't have resistance that does not mean that the
PPO of your post emergence will work as effectively as you would like to. So here
we have a tray and this plants here were actually treated with Pursuit or Imazethapyr
a group two herbicide ALS resistance in water hemp and Palmer
Amaranth is quite widespread and this what we're seeing here Pursuit sprayed
post emergence barely touched this plants when when used at the label rate
okay. Other two treatments I want to discuss here we have atrazine and here
we have mesotrione or Callisto our atrazine was sprayed at four pints per
acre and the Kalista was sprayed at three fluid ounces per acre. On the
atrazine treatment here when sprayed post emergence as you can see here the
response is varying but especially for our Wisconsin population here we
couldn't get a good or complete kill post emergence okay. And a similar
scenario here for mesotrione or Callisto we could not get a complete kill,
even though these plants are highly injured they're still alive okay. So
remember this herbicides were sprayed post emergence to two and a half to
four inch tall plants. Felipe is going to conduct how the screenings looking at
tolerance when this herbicides are sprayed pre-emergence okay, because this
particular Callisto and atrazine are commonly used in our state and and
around us as part of a pre-emergent herbicide program so we want to see how
this populations respond when used in a pre versus a post
fashion. All right so these are the three last herbicides I want to talk about and
these are very important herbicides for our current and production systems here
I have the Dicamba, 24D, and Liberty okay. The three herbicides can now be used in
some of the novel traded technologies your Extend, your Enlist and Liberty
system. So again it's the systems are you know herbicides specific there. The first
one I want to discuss is Dicamba here okay.
And as you can see here even though we got good suppression it was difficult to
get a complete kill of the Palmer Amaranth and a similar scenario for our
24D again for both populations the population from western Nebraska and
also the population that we found here in Wisconsin okay. So both Dicamba and
24D our growth regulator herbicides and even though they seem to be doing a
decent job we couldn't get a complete kill and they're okay. The last one here
is Liberty and in this comparisons here the two populations that I have Liberty
was the only herbicide that provided complete kill of our plants so 100%
control. There is a lot of interest in the traits they can be helpful
however we our farmers have to be very wise how they use them okay there's
particularly a lot of interest around the the Liberty technology is very
effective on the big weeds however if going that route farmers must
be spraying small weeds and that's true for all herbicides post emergence but
particularly for Liberty which is a post emergent herbicide and to this point
scientists have not reported pigweed resistance to Liberty ok. So we gotta use
this herbicides not only Liberty but also the Dicamba and 24D
particularly in our soybean systems in a wise fashion ok. So the take-home message
here we have Palmer amaranth kind of coming into the state and when it comes
in it comes in with resistance as we saw we glyphosate didn't touch it
in Imazethapyr didn't kill it and was difficult to control with the PPO
and then the control level with the other herbicides that we have here post
emergence was highly variable ok. So it's important to detect when the weed is
present adopt a sound management practice to prevent it from establishing
interfused and establishing around our communities here. So with that thank you
for your attention