How Well Do You Know Your Enemy?
BROCK WAGGONER
COLUMBIA, MO.
Last season, we conducted the first year of a
two-year survey to identify the most common
weed species encountered in Missouri
corn and soybean fields, and to better understand
the management practices that producers
are utilizing for the control of these species.
In this article, we will discuss the most common
weeds that were found in corn and soybean
fields in 2011. In a subsequent article, we will
explain our findings as it relates to the management
practices that producers are utilizing
for the control of these species in Missouri. This
survey was primarily conducted throughout the
northern half of the state across 50 different locations
in 2011, and will be conducted in a similar
number of locations throughout the state in
2012.
In 2011, we identified 23 different broadleaf
and 10 different grass weed species in the corn
fields that were surveyed. The top 10
most common species were waterhemp,
morningglory species, yellow
nutsedge, goosegrass, cocklebur, foxtail
species, fall panicum, prickly sida,
horsenettle, and velvetleaf (Figure 1).
In the soybean fields that were surveyed
there were 51 different broadleaf
and 13 different grass weed species.
Waterhemp and the morningglory
species were again the top two most
common species identified, with 87
percent of the soybean fields containing
waterhemp (Figure 2). The other 8
species that rounded out the top 10
were prickly sida, fall panicum, velvetleaf,
cocklebur, foxtail species,
horseweed, large crabgrass, and horsenettle.
If you are at all familiar with Missouri
agriculture, there are plenty of
things about the results in Figures 1
and 2 that are probably not all that
surprising to you. For example, the
fact that waterhemp is our most common
species encountered in soybean
fields is probably not a big surprise to
anybody. However, there are some
other species that made these top 10
lists that probably would not have
been on those lists 5 or 10 years ago.
Although we have no previous weed
surveys to compare this data to, one of
the species that seems to be occurring
with more frequency in recent years is
fall panicum. This grass tends to be
one of our later germinating species, and as
such may escape the timing of our herbicide applications,
especially in corn fields. Other weeds
on these lists that are likely occurring with
more frequency now than in the past include
goosegrass and prickly sida.
Whatever weeds you have in your fields, it’s
important for you to know what they are in
order for you to manage them appropriately. If
you aren’t certain of what weed species you
have in your fields, we have an online weed id
guide that can help. You can go to:http://weedid.missouri.edu/index.cfm , select whether
your weed is a broadleaf or grass weed, and
then use the keying system and select the appropriate
answer to the remaining questions
about your unknown species in order to narrow
down the possibilities. Δ
DR. KEVIN BRADLEY: Associate Professor
Plant Pathology, University of Missouri
BROCK WAGGONER: Graduate Research Assistant,
University of Missouri