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Fall Weed Survey Completed
Waterhemp found
in 25% of Darke County Soybean Fields
By Sam Custer
OSU Extension, Darke County
I completed the Fall Soybean Weed Survey in Darke County with the
assistance of Weed Scientist, Dr. Jeff Stachler, Darke County native
and Auglaize County Extension Educator. The good news is that we have
several parts of the county where growers are managing their resistant
weed problems. The assumption is that most of Ohio soybeans are
RoundupReady, and that if weeds are still in the soybean field at the
end of the season, then there must have been a failure of the system –
not always correct but then we are making assumptions that may not be
too far off.
The Fall Soybean Weed Survey is completed by Extension Agriculture
Educators across the state to evaluate weed pressure and to determine
the levels of resistance that has been built in the different regions
of the state. Each educator is asked to drive an 80 mile loop
around their county and to evaluate the soybean fields at one mile
increments.
We drove an 89 mile loop and evaluated 91 soybean fields for all weed
species, because of the concern for resistant waterhemp showing up in
Western Ohio we looked at all 309 fields in the loop to determine if
there was waterhemp in the field.
We found only 12% of the 91 fields completely void of weeds and
volunteer corn compared to about 40% the previous two years. An
occasional weed or corn plant could be found in another 15% of the
fields.
So what species of weeds did we find in Darke County: Voluntary corn,
48%; Giant Ragweed, 43%; Marestail, 41%; Waterhemp, 25%; Velvetleaf,
22%; Common Lambsquarter, 19%; Giant foxtail/grass, 19%; Smooth
pigweed, 9%; Morning glory, 8%; Pokeweed, 2%; Common Ragweed, 1%;
Honeyvine Milkweed, 1%; Redroot Pigweed, 0.
So what is my takeaway from the tour of Darke County last Friday?
Dr. Stachler and I spent a lot of time talking about that very question
while we were finishing up.
First, Mother Nature was not friendly to weed management in 2016.
We probably have 7 species of weeds in Darke County that are at least
partially resistant to glyphosate.
We have some growers that are very successful in their weed management.
Tillage alone, which was once thought to be a great way to control
marestail, is not working anymore.
WATERHEMP. Not much different than the dreaded Palmer Amaranth,
is a severe problem. We found waterhemp in 66 of the 309 total fields
we drove by in the 89 mile loop. Our estimate is that 44% of the
fields in the north and western part of the county are infested.
What action needs to be taken?
Scout your fields for waterhemp NOW. If you have a few plants,
pull them out carefully and place them in a bag and incernerate
them. DO NOT run them thru the combine. Each plant has over a
million seeds that you will quickly spread across the field and in to
other fields.
Attend our pesticide meetings this winter. Mark your calendar
today for February 7 to hear from weed scientists Dr. Mark Loux and Dr.
Jeff Stachler give their recommendations for getting waterhemp off your
farm or to prevent it from entering your farm.
Determine whether your waterhemp population is resistant to glyphosate
and/or site 14 herbicides. Fortunately, there is a painless way
to do this, through a service offered by the University of Illinois
Plant Clinic. Link to the U of I newsletter article that provides
the needed info - http://bulletin.ipm.illinois.edu/?p=3619.
The LibertyLink soybean system is, of course, another option for
management of waterhemp, as well as Xtend and Enlist soybean systems
whenever they become available.
It should be noted that: 1) use of glufosinate, dicamba, or 2,4-D to
help manage this weed does not change the approach, and these
herbicides must be applied to small plants to control waterhemp; and 2)
the assumption is that inappropriate and continued use of these
herbicides would lead to the development of resistance to them.
And in fact there are already some populations of waterhemp farther
west with resistance to 2,4-D.
For more information about OSU Extension, Darke County, visit the Darke
County OSU Extension web site at www.darke.osu.edu, the OSU Extension
Darke County Facebook page or contact Sam Custer, at 937.548.5215.
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