GENET archive


2-Plants: US study shows no cost advantages by using Roundup Ultra in RR-corn

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TITLE:  Comparision of weed management strategies with Roundup
        Ready corn
SOURCE: University of Kentucky, USA, by J.A.Ferrell & W.W.Witt
DATE:   January 2000

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Comparision of weed management strategies with Roundup Ready corn 

(For full text and tables go to


Corn weed management during the past several years in Kentucky
has centered around two herbicide families, the chloroacetamides
(Dual, Frontier, Harness, Micro-Tech, Surpass) and the s-
triazines (AAtrex, Bladex, Princep). These products have been
used widely because they offer acceptable, full season control of
many common warm season annual weeds at a reasonable price. This
combination has been so popular that several premixtures that
contain these types of herbicides (Bicep II, Bullet, Guardsman,
Harness Xtra, Surpass 100, FulTime) are used commonly used in
Kentucky. The key to this efficacious and economic program is
atrazine because it controls most annual broadleaf species that
exist in Kentucky corn production with minimal economic

In addition to a good foundation soil-applied herbicide program
for controlling annual weeds, a postemergence application of
nicosulfuron (Accent) is often needed to help manage johnsongrass
(Sorghum halepense). Including nicosulfuron as a part of a weed
control program increases costs and may increase risk of corn
injury due to antagonism with certain insecticides or untimely

Monsanto released Roundup Ready corn, which is a transgenic crop
that is tolerant to glyphosate, in the spring of 1998. Glyphosate
is the active ingredient in several products including Roundup
Ultra and has long been used as a non-selective burndown
herbicide for no-till production of grain crops. The Roundup
Ready technology allows corn growers the opportunity to use
Roundup Ultra as a tool for managing most annual grass and
broadleaf weeds as well as johnsongrass and other perennial

Although Roundup Ultra was known to control a wide range of weedy
species, there were questions regarding the economics of this
technology relative to traditional standard herbicide programs
for controlling warm-season annual weeds. The technology fee of
$6 per acre for the Roundup Ready seed was an expense associated
with a Roundup weed control program. Furthermore, it was not
known if one or two applications of Roundup Ultra would be needed
to provide weed control comparable to other products.

The first objective of this research was to compare the
effectiveness of Roundup Readył technology with other herbicide
options for managing johnsongrass. A second objective was to
compare the profitability of Roundup Ready technology with
traditional herbicide programs for managing warm-season annual



These results demonstrated that Roundup Ultra can be used
alone, or sequentially with other products, to deliver effective
and consistent weed control over a range of weed species and
environmental conditions. There were no differences in return
above fixed and variable costs between Roundup Ultra and any of
the other herbicide programs compared in this study. Roundup
Ready technology provides another weed management alternative
for Kentucky corn growers.

The two years in which these studies were conducted were very
different. Growing conditions in 1998 were excellent for corn
production resulting in excellent yields in Lexington and
Princeton while rainfall was lacking at both locations in 1999
and corn yield was reduced greatly. The extremes in growing
conditions provided an opportunity to evaluate Roundup Ready
technology under the "best" and "worst" cases that will be
encountered in Kentucky. Consistent weed control was obtained
with all herbicide treatments in both years. 


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