Hi, I'm Daniel Smith, Southwest Regional Agronomist for the University of Wisconsin-Madison and
UW-Extension's Nutrient & Pest Management Program. And today, I'm going to talk to you
about waterhemp seed dispersal. So, if you look at waterhemp seed dispersal, once of
the most common ways waterhemp seeds can move throughout a field is movement through a combine.
So, you see in this Year 1 photo: A small patch of waterhemp plants that maybe have
gotten missed by a herbicide pass or maybe germinated after the herbicide pass. That's
producing viable seed and out in the field, at harvest time, the farmer makes the decision
to go ahead and harvest that patch of weeds and put that seed into the combine. So, then
on Year 2, after the nice, 30 foot-wide strip of waterhemp seeds, of waterhemp plants, rather,
spread throughout the field. And then, finally, this farmer makes the decision to harvest
again and spreads out waterhemp seed throughout the entire field. And these photos do a nice
job of illustrating what can happen if we allow waterhemp to go to seed and then run
that seed throughout a combine. And they were taken by the Ohio State University. If we
look at waterhemp seed and why it makes it so tricky to hide in the columbines is the
seed size. So if you'll look at the seed compared to the penny and the pinhead, you can see
it's a small, black, shiny seed and it can very easily hide in our equipment and spread
from within the field and then from field to field. If we look at where a seed can hide
in a columbine, we start to think about where that tiny black seed can hide in all the nooks
and well joints and such in a combine. And if we start to look at combines and where
the residue hides, this photo's a fairly new combine that was extremely clean when we showed
up at the producer's farm and had been cleaned from top to bottom, front to back, power-washed
inside and out and it was a very nice combine. However, we still are going to find a little
bit of biomass material that could be hiding these seeds in some of those well joints and
cracks and crevices in the combine, such as where the feeder house and the head meet,
and then right below the roter region there's a small area that could hide some weed seeds.
So, once we've started to think about weed seeds and where they can hide in a combine,
it can help us clean a combine a little bit better. If we look at some research that's
been done on this from Iowa State University, and then thus published in a Purdue Publication,
we see that the header has quite a bit of pounds of biomass that was collected during
a combine cleanout, as does the feederhouse, the rocktrap, the grain tank and unload auger
regions. And these areas all can be easily cleaned either by opening a door, maybe running
the combine with those doors open, using some straw to pack in those areas and clean those
areas by running the combine again, or just simply using a leaf blower-- some compressed
air-- we can quickly clean a combine in say, thirty minutes or less to minimize the risk
of moving weed seeds from field to field. A complete combine cleanout, however, we can
expect to spend 4-8 hours depending on how thorough and what methods we choose to use
to completely clean the combine. And this would be done when we're switching grains
and switching from a GMO to a non-GMO grain and that type of thing. However, with just
a simple investment of thirty minutes or so, we can quickly clean out the most troublesome
regions with a leafblower. Another way waterhemp seeds can move is through waterfowl. Waterfowl
can in fact move quite a few weed-seeds as they eat them and ingest those weedseeds and
they carry them from field to field, from region to region, even. Some recent research
from the University of Missouri looked at this in detail and they worked with sportman
that harvested waterfowl to examine and then dissect what kind of weed seeds these waterfowl
were carrying. And we see quite a number of waterhemp seeds were being carried by these
waterfowl. If we look at this table 3, we see there is 362 waterfowl sampled in this
study and we see that waterhemp was one of the primary weed seed species found. There
is 3654 plants they found in the esophogus region, which totaled for about 37%. In the
gizzard, there was 444 weeds and then in the intestines there was 146 and these were all
waterhemp plants that germinated after growing out of those seeds that they found in those
regions. So, obviously, could be a troublesome way that waterhemp seeds are spreading from
field to field and within regions. If we look at waterfowl hemp movement, and likely the
waterfowl in this study were traveling through the Devil's Lake region of North Dakota, as
illustrated in the fact that green ducks were in this study, but, in the Mississippi River
Valley region, the blue ducks are representing. These ducks could have also been included
in the study, and they do travel through the Wisconsin and greater Upper Midwest region.
So, something to be thinking about, if these waterfowl are visiting our farms, maybe they're
bringing us some waterhemp seeds and something to scout for. This is further influenced if
we look at a map of where waterhemp has been found in Wisconsin vs. waterways in Wisconsin.
So, we will look at first, the Mississippi region, we see quite a few dots along that
side of the state of Wisconsin. Clearly, some waterhemp is present in that region. Moving
further into Wisconsin, we see the Wisconsin River region and again, waterhemp seeds along
that river suggest we're getting some waterfowl movement. We look at the Lake Winnebago Region,
again, some more waterhemp seeds. And then up into the Lake Michigan Region. If we look
at the Chippewa flowage region, we see some waterhemp seed movement again. And so, we
could hypothesize that waterhemp is being moved by waterfowl in Wisconsin. It's something
to scout for if we're having a lot of waterfowl visit our farm. Another way we can see waterhemp
seeds move on our farm is through the seed, feed and bedding we use. So, one of the most
common ways we've seen palmer amaranth come through some of our dairy farms is through
cotton seed. So, if we're using some of these additives in our rations, we certainly should
be doing some scouting for these troublesome weeds so we can prevent them from going to
seed. If we're taking some manure from a neighbor who's using some of these ingredients in their
ration, again, we should be scouting for these weeds seeds and preventing the weeds from
going to seed after they germinate. And then finally, buying certified seed. So, if we're
going to be doing any conservation and cover crop plantings, we should be buying certified
seed. And if we choose to use binrun seed, we should run a seed analysis test to see
if there is any weed seeds in that that we should be concerned about. If we look at waterhemp
seed dispersal, this year we've had a lot of flooding, we can think about what that
water carries in it, we could hypothesize that waterhemp seed was being floated from
one field to another in this water if our neighbors had waterhemp, it could be easy
that that seed could be floating and moved on to our property. So, if we're seeing some
movement from neighbors to our field or vice versa, we should be scouting and seeing if
that seed had moved through that water or not. All this scouting is to prevent the weed
seeds from causing us future problems. So, we know that immediately, in this current
field season, yield loss can occur from competition from all of those weed seeds germinating and
producing a lot of weed to cause us trouble. We look at that because we're competing for
light, water and soil fertility resources. So, this first photo of the soybean field
shows the power of waterhemp seed and how much can germinate and how much can spread
from a reltively small population of waterhemp. And think about the yield implications that
may have. And then to illustrate those yield implications, I've included a photo of a giant
ragweed field in Rock County and showing that corn next to my hand and how great that yield
impact is economically. And obviously, something that we should invest in to prevent from recurring.
If we look at some future costs of waterhemp seed management: First, is going to be hand
pulling. In the south, it's quite common to hand-pull palmer amaranth and waterhemp and
it's fairly costly per acre. We think about field herbicide attempts: From having herbicide
resistance develop and spread, obviously cost of tillage, not alone, we have our field costs
and our equipment wear-and-tear costs and then we have the cost of soil erosion and
tillage conservation consequences. We have yield loss recurring into future years from
this weed population. We have the increased cost to reduce the seed bank by utilizing
more herbicide passes, maybe utilizing more tillage, utilizing more crop rotation techniques
to try and control those weed seeds from spreading, and then we have some export restrictions.
So, other countries are becoming more mindful as the Weed Science Society of America article
suggests. China is becoming more interested in what kind of weed seeds we're exporting.
Finally, this piece of equipment shown in the photo with the combine is a Herrington
Seed Destroyer and it was developed by a farmer in Australia named Ray Herrington. It's a
cage mill and it takes the biomass from the combine and it will crack the seed coat off
of any weed seeds that go through that machine, thus making them no longer viable when they
go out and sit on the ground, they decompose. Looking at preventing waterhemp seed movement,
we want to avoid seed production, so obviously you want to use good pre-emergent herbicides,
we want to use good cultural managment techniques to prevent that weed seed from ever developing.
We want to clean our equipment. So, we want to clean our combines, we want to clean our
planting equipment, we want to clean our tillage equipment to make sure that it doesn't spread
weedseeds from field to field. We want to harvest any fields with resistance last. So,
these fields that have heavy infestations of waterhemp that we know have maybe herbicide
resistance, save those until the end of the harvest season & then do a final combine cleanout
after harvesting that field, that way we don't spread that field of waterhemp seed to another
field. Finally, we want to manage our field borders, our field waterways, our road ditches,
to prevent those weed seeds from migrating from those regions into the field. That can
be a very important aspect of weed management that we often forget about, is allowing those
areas to go to seed and then once they go to seed, they migrate farther into our field
and they can start to cause us economic yield losses. That concludes my presentation today,
I'd welcome any questions through email and phone conversations and I encourage you to
follow up with your local extension educator for more information.