C R O P
M A N A G E M E N T
S O L U T I O N S
IN-SEASON WEED CONTROL OPTIONS FOR GRAIN SORGHUM
What You’ll Learn...
 POST herbicide applications should be made
early in the season when weeds are small
and there is less risk of injury to grain
sorghum in the reproductive stages
 Herbicide options for control of tall emerged
grasses are limited
 Broadleaf weeds may compete with grain
sorghum but can be controlled by several
selective herbicides
 Awareness of weed tolerance to herbicides,
weed height, and maximum seasonal use
rates of herbicide products are important
for POST weed management in grain
sorghum
Timing Weed Control
Application timing is important for optimum herbicide
performance and to avoid unacceptable crop injury.
Small grass and broadleaf weeds that are 2 to 4
inches tall are easier to control compared to taller
weeds. Weed control the first four weeks after grain
sorghum emergence is reported to be the most
critical period of weed control.1
Crop injury from in-crop herbicide applications can
occur if using improper additives, tank-mix partners,
or timing. It is important to read label directions as
different brands and label updates could differ from
one year to the next. Drop nozzles are recommended
for several herbicide applications in tall grain
sorghum and this equipment should be available in
case delayed.
Weed Spectrum
Yield losses from weed competition are greater
in sorghum compared to most grain crops. As
much as 30 to 50 percent yield loss can be
associated with weed competition.1 Potentially
one pigweed plant per 3 foot of row, left
uncontrolled until sorghum reaches the threeleaf stage, can reduce yield potential by 10%.2
However, grass weeds can be more difficult to
control due to the lack of selective herbicides.
Heavy infestations of grassy weeds may cause
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up to a 20% yield reduction in the first two weeks
after sorghum germination.2
POST Herbicide Options
Species such as Johnsongrass and shattercane may
be a challenge to control as they are biologically
similar to cultivated sorghum. Johnsongrass is a
perennial and, unlike in corn, does not have a
selective herbicide option in sorghum. In general,
there are limited herbicide options for emerged grass
weeds in sorghum. Some small grasses may be
controlled with an overhead application of atrazine.
Atrazine has also been commonly tank-mixed for
postemergence broadleaf weed control in sorghum.
Maximum use rates should be recognized for atrazine
if sensitive crops are planned for next season. Small
pigweed and waterhemp weeds can be controlled with
a tank-mix or pre-packaged herbicide. Herbicide
products should be rotated and chosen based on past
activity for the weed spectrum of a field. Over time,
pigweeds and waterhemp can develop tolerance to
herbicide families.
Sorghum seeds treated with a safener (such as
Concep® III) can be safely grown in soil treated with
Warrant® Herbicide and Degree Xtra® herbicides.
Warrant Herbicide and Degree Xtra can also be POSTapplied and are residual herbicides that have active
ingredients from the chloroacetamide family.
Safeners protect sorghum from potential injury from
herbicides in the chloroacetamide family. Warrant
Herbicide and Degree Xtra are important products
that can control annual grasses and late flushes of
small-seeded broadleaf weeds such as pigweeds.
Sources: 1 Weed control. West Texas Production Guide. Sorghum CheckoffSM. Mobile Production
Guides. 2 Smith, K. and Scott, B. Weed control in grain sorghum. Grain Sorghum Production HandbookMP297. University of Arkansas. p. 47.
Figure 1. Sorgum bicolor
(left) is grain sorghum
and biologically similar
to Sorghum halapense
(right) or Johnsongrass,
a grass weed of grain
sorghum. Johnsongrass
is a perennial and
patches may be
controlled with wiper
applications of Roundup
WeatherMAX® before
grain sorghum heads.
Photo courtesy: Steve Dewey, Utah
State University, Bugwood.org
C R O P
M A N A G E M E N T
S O L U T I O N S
IN-SEASON WEED CONTROL OPTIONS FOR GRAIN SORGHUM
Table 1. POST Herbicide Options for Broadleaf Control in Sorghum*
Common Name (brand) Sorghum Height Recommendation
Atrazine
(Aatrex®)
Comments
Apply when sorghum is 6 to 12 inches Apply before pigweed species reach 6 inches
tall (drop nozzles after crop is 12
Carryover injury can occur if there is little seasonal
inches)
rain
Acetochlor + Atrazine
Apply until sorghum is 11 inches tall
Avoid using liquid fertilizer carriers
Do not apply with a temperature forecast of 85° F
within 24 of application
Apply until sorghum is 11 inches tall
Avoid using liquid fertilizer carriers
From 6 to 15 inches (drop nozzles
when taller than 8 inches)
Do not apply during boot, flowering, or dough stages
®
(Degree Xtra )
Acetochlor
®
(Warrant Herbicide)
2,4-D amine 4
2,4-D LV6
Dicamba
(Banvel®, Clarity®)
Prosulfuron
(Peak®)
Fluroxypyr
(Starane® Ultra)
From spike to prior to 15 inches (drop Performance may be best when applied to sorghum
between the 3 and 5 leaf stages and weeds are less
nozzles when taller than 8 inches)
than 3 inches
5 to 30 inches before head
emergence
Crop oil concentrate (COC) is preferred over nonionic surfactant (NIS) for additives in drier climates
3 to 7-leaf (drop nozzles for 7-leaf up Use NIS for additive
to boot stage)
Good control for kochia and morningglory
Carfentrazone-ethyl
(Aim® EW)
Through 6-leaf stage
NIS recommended at 0.25% v/v
Effective on small weeds
Halosulfuron
(Permit® Herbicide)
2-leaf through layby stage before
head emergence
NIS at 0.25% v/v as and additive
Weak on pigweed control
3 to 15 inches before boot stage (use
drop nozzles over 10 inch height)
Do not use surfactant or crop oil additives
Apply when weed heights are less than 6 inches
3-leaf to prior to preboot stage in
grain sorghum (recommended rates
differ)
Leaf burn may occur with spray additives
Often combined with atrazine
Directed sprays after 15-inch height
Lower rates for small broadleaves and higher rates
for grasses and taller broadleaves
3-leaf to 30-inch (prior to flag leaf
emergence)
Best performance on weeds 4 inches or less.
Negative crop response can occur
Metsulfuron
®
(Ally XP)
Bromoxynil
®
(Buctril 2E or
Buctril® 4EC)
Diuron
(Direx®)
Pyrasulfotole +
bromoxynil
(Huskie®)
Halosulfuron + dicamba 2-leaf through 15 inches (drop
nozzles in sorghum greater than 8
(Yukon®)
inches)
COC or NIS recommended additives
* Not exclusive, other brand names may be available depending on location
Sources: Weed control. West Texas Production Guide. Sorghum CheckoffSM. Mobile Production Guides.
Trostle, C. and Bean, B. 2014. Quick guide for weed control and harvest desiccation in Texas grain sorghum-2014. Texas A&M AgriLife Extension.
For additional information, contact your local seed representative. Developed in partnership with technology, Development & Agronomy by Monsanto.
Roundup Technology® includes Monsanto's glyphosate-based herbicide technologies. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Warrant® Herbicide is not registered in all states.
Warrant® Herbicide may be subject to use restrictions in some states. Degree Xtra® is a restricted use pesticide and is not registered in all states. The distribution, sale, or use of an unregistered pesticide
is a violation of federal and/or state law and is strictly prohibited. Check with your local Monsanto dealer or representative for the product registration status in your state. Tank mixtures: The applicable
labeling for each product must be in the possession of the user at the time of application. Follow applicable use instructions, including application rates, precautions and restrictions of each product used in
the tank mixture. Monsanto has not tested all tank mix product formulations for compatibility or performance other than specifically listed by brand name. Always predetermine the compatibility of tank
mixtures by mixing small proportional quantities in advance. Degree Xtra®, Roundup Ready PLUS®, Roundup Technology®, Roundup WeatherMAX® and Warrant® are registered trademarks of Monsanto
Technology LLC. Permit® and YUKON® is a registered trademark of, and used under license from, Nissan Chemical Industries, Ltd. Direx® is a registered trademark of E.I. Du Pont de Nemours and
Company. All other trademarks are the property of their respective owners. ©2015 Monsanto Company.150410115110 042715SEK
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