Volunteer Peanut (Arachis hypogaea L.) Control in Glyphosate/Glufosinate 
Resistant Cotton (Gossypium hirsutum L.) 
 
by 
 
Brandon Aaron Dillard 
 
 
 
 
A thesis submitted to the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
requirements for the Degree of 
Master of Science 
 
Auburn, Alabama 
May 6, 2012 
 
 
 
 
Keywords: volunteer, peanut, cotton, glyphosate,  
glufosinate, resistance 
 
Copyright 2012 by Brandon A. Dillard 
 
 
Approved by 
 
Dr. Andrew J. Price, Chair, USDA-ARS-NSDL 
Dr. Charles D. Monks, Extension Specialist and Associate Professor of Agronomy and 
Soils 
Dr. Michael G. Patterson, Extension Specialist and Associate Professor of Agronomy and 
Soils 
 
 
 
 
 
 
ii 
 
Abstract 
 
 
 The increase in conservation tillage along with the use of herbicide-resistant crops 
has changed the dynamics of weed populations and control methods with volunteer plants 
from the previous crop contributing to the weed community in subsequent rotations.  In 
the southeastern U.S., a peanut-cotton rotation is very popular for disease, insect, weed, 
and nematode suppression; however, volunteer peanut plants can be challenging to 
control in cotton production.  Field experiments were conducted in 2010 at the Gulf 
Coast and Wiregrass Research and Extension Centers to identify effective control 
strategies for volunteer peanut in cotton.  RoundUp Ready? and LibertyLink? cotton was 
planted in plots where peanuts were produced in 2009.   Plots were sprayed at the 
cotton?s 2-leaf, 4-leaf, or 2 and 4-leaf growth stage with either a postemergence (POST) 
glyphosate (1.12 kg ai ha-1) or glufosinate (0.47 kg ai ha-1) application alone or followed 
by trifloxysulfuron-sodium (0.005 kg ai ha-1) applied at the 8-leaf growth stage.   In 
addition, all plots received prometryn (1.12 kg ai ha-1) + monosodium acid 
methanearsonate (MSMA) (2.24 kg ai ha-1) as a post-directed spray (LAYBY) to cotton.   
At the Wiregrass Research and Extension Center, the 2-leaf or 4-leaf alone treatment 
provided ? 30% control.  The 4+8-leaf treatment provided poor early control, < 55 %, but 
control increased to ? 65% over time.  The best control was observed in the 2+4+8-leaf 
and 2+8-leaf treatments.  However, only 70-75% control was attained in this study 
indicating significant peanut survival.  There was no significant difference in control of 
volunteer peanuts with glyphosate or glufosinate systems.  At the Gulf Coast Research 
and Extension Center, better overall volunteer peanut control, ranging from 93% to 20% 
across all treatments, was observed.   The only treatment that provided significantly 
lower control than the weed free treatment at the late rating was the 2-leaf alone 
application at ? 20 % control.   At this location there was also an advantage in using a 
glufosinate system at both 4-leaf and 8-leaf ratings.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Acknowledgments 
 
 
 This work is dedicated to my late grandfather, Millard F. Dillard.  I would not 
have developed the love and respect for agriculture that I have today if not for him.  
Thanks to all of my family, especially my wife Nicole, who have understood the late 
hours and my commitment to this research.  Thank you for the support and motivation to 
finish this project.  Thanks to Jessica Kelton, who has spent several hours in the field and 
on the phone, for assisting me in completing this thesis.  I sincerely appreciate all of the 
help from the Wiregrass and Gulf Coast Research and Extension Centers.  The staff was 
wonderful at both locations.  And finally, I would like to express my deep gratitude to my 
committee members for their guidance through this process.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
v 
 
Table of Contents 
 
 
Abstract .................................................................................................................................... ii 
Acknowledgments  .................................................................................................................. iv 
List of Figures ......................................................................................................................... vi 
Introduction   ............................................................................................................................ 1 
 Cotton and peanut crop rotations   ................................................................................. 1 
 Conservation tillage in southern row crops   .................................................................. 2 
 Peanut maturity and harvest   ........................................................................................ 3 
 Harvesting peanuts in dry and wet soils   ....................................................................... 4 
 Peanut harvest losses   ................................................................................................... 4 
 Weed competition in peanuts  ....................................................................................... 5 
 Cotton weed management   ........................................................................................... 6 
 Volunteer peanut harboring effect on cotton production   .............................................. 8 
 Controlling volunteer peanut in cotton  ......................................................................... 8 
Materials and Methods  ............................................................................................................ 9 
Results and Discussion   ......................................................................................................... 11 
            Weed control............................................................................................................... 11 
            Yield ........................................................................................................................... 14  
References   ............................................................................................................................ 16 
 
vi 
 
List of Figures 
 
 
Figure 1. Control of volunteer peanut following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 2-leaf stage at Wiregrass Research and 
Extension Center, Headland, AL.. ........................................................................................... 20 
 
Figure 2. Control of various grass species following postemergence herbicide on cotton at 
2-leaf stage at Wiregrass Research and Extension Center, Headland, AL ................................ 21 
 
Figure 3. Control of volunteer peanut following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 4-leaf stage at Wiregrass Research and 
Extension Center, Headland, AL. ............................................................................................ 22 
 
Figure 4. Control of various grass species following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 4-leaf stage at Wiregrass Research and 
Extension Center, Headland, AL. ............................................................................................ 23 
 
Figure 5.  Control of volunteer peanut following postemergence herbicide on cotton at 8-
leaf stage at Wiregrass Research and Extension Center, Headland, AL ................................... 24 
 
Figure 6. Control of various grass species following postemergence herbicide on cotton at 
8-leaf stage at Wiregrass Research and Extension Center, Headland, AL. ............................... 25 
 
Figure 7. Comparing glyphosate and glufosinate control of various grass species at 
Wiregrass Research and Extension Center, Headland, AL ...................................................... 26 
 
Figure 8. Control of volunteer peanut following postemergence herbicide on cotton at 8-
leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL. .................................. 27 
 
Figure 9. Control of various grass species following postemergence herbicide on cotton at 
8-leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL   .............................. 28 
 
Figure 10. Control of volunteer peanut following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 2-leaf stage at Gulf Coast Research 
and Extension Center, Fairhope, AL ....................................................................................... 29 
 
Figure 11. Control of various grass species following postemergence herbicide at cotton 
at 2-leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL... ......................... 30 
 
Figure 12. Control of volunteer peanut following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 4-leaf stage at Gulf Coast Research 
and Extension Center, Fairhope, AL. ...................................................................................... 31 
 
Figure 13. Control of various grass species following postemergence applications of 
glyphosate and glufosinate herbicides on cotton at 4-leaf stage at Gulf Coast Research 
and Extension Center, Fairhope, AL. ...................................................................................... 32 
 
Figure 14. Comparing glyphosate and glufosinate control of volunteer peanut at Gulf 
Coast Research and Extension Center, Fairhope, AL .............................................................. 33 
 
Figure 15. Comparing glyphosate and glufosinate control of various grass species at Gulf 
Coast Research and Extension Center, Fairhope, AL. ............................................................. 34 
 
Figure 16. Cotton lint yield (kg ha-1) at Wiregrass Research and Extension Center, 
Headland, AL... ...................................................................................................................... 35 
 
Figure 17.Comparison of RoundUp Ready Cotton Lint Yield vs. LibertyLink Cotton Lint 
Yield at Wiregrass Research and Extension Center, Headland, AL.. ....................................... 36 
 
Figure 18.Cotton lint yield (kg ha-1) at Gulf Coast Research and Extension Center, 
Fairhope, AL. ......................................................................................................................... 37
1 
 
Introduction 
 
 Agriculture is America?s most important export industry (ACES, 2000).  In fact, 
agricultural exports averaged $40 billion in 2009.  However, these export levels may not 
be sustainable with the continuous battles over water usage, increased energy costs, and 
climatic changes (Batie and Healy, 2009).   One American farmer feeds 130 people each 
year, 25 who live overseas (ACES, 2000).  Approximately seventy-nine cents of every 
dollar that the average American spends on food goes toward processing and marketing, 
leaving the farmer with only 21%  to pay for all variable costs such as seed, fertilizers, 
herbicides, fungicides, diesel fuel in addition to fixed costs like tractors and facilities, 
leaving little net income for the farmer.   
Cotton and peanut crop rotations.  Peanut (Arachis hypogaea L.) and cotton 
(Gossypium hirsutum L.) crop rotations are typically grown in the southeast United States 
and are valuable to farmers for reducing nematode and disease pressure, which can aid in 
increasing yield. The rotation of peanut with cotton can reduce the number of peanut 
root-knot nematode [(Meloidogyne arenaria (Neal) Chitwood)] and increase yield while 
reducing nematicide usage (Rodriguez-Kabana, et al, 1986).  A six-year study at the 
Wiregrass Research and Extension Center, Headland, AL. indicated that peanut yield 
following one or two years of cotton were consistently higher than continuous peanut 
plantings.  In this experiment, the addition of a nematicide to continuous peanut rotation 
did not improve yields over the peanut-cotton rotation alone.   Rodriguez-Kabana, et al 
(1991) determined that peanut root-knot populations were lowest following cotton.  The 
same effect is seen with cotton root-knot nematode (Meloidogyne incognita Race 3) on 
peanut. Peanut is considered to be a ?passive? control measure for cotton root-knot 
2 
 
nematode, as it is simply a non-host (Rodriguez-Kabana and Canullo, 1992).  Where high 
infestations of cotton root-knot nematodes are observed, rotating to peanut will decrease 
nematode numbers unlike monoculture systems of cotton or corn (Zea maize L.) 
(Kirkpatrick and Sasser, 1984).   
Crop rotations also benefit cotton and peanut production in the southeastern 
United States by decreasing soil diseases.  One economically important soil-borne disease 
that affects peanut growth and yield is southern stem rot, Sclerotium rolfsii Sacc. 
Southern stem rot can be reduced in peanut through rotation to crops like cotton, corn, or 
bahiagrass (Rodriguez-Kabana, et al, 1991; Mullen, 2006).  The incidence of southern 
stem rot is typically found to be greater when shorter rotation intervals away from peanut 
are attempted.  In 1993, Bowen, et al found that southern stem rot had a higher degree of 
occurrence in fields cropped to peanut every other year compared to longer rotations.  
Other production practices used for managing southern stem rot include fungicides and 
inversion tillage.  For many years producers fought this disease with inversion tillage as 
their only tool.  However, research has shown a direct relationship in organic matter at 
the soil surface to peanut losses from southern stem rot (Brenneman, et al, 1999).    
Recently discovered fungicides with increased effectiveness on southern stem rot have 
decreased the need for tillage. However, they are only partially effective in decreasing the 
risk of large losses of peanut yield and quality of peanut (Hagan, et al, 2001).   
Conservation tillage in Southern row crops.  Conservation tillage is becoming widely 
adopted by row crop growers in the U.S.  Of the 2.9 million hectares of cotton planted in 
2004, nearly half was planted in some form of conservation tillage an increase from prior 
years (CTIC, 2004).  Conservation tillage can result in reduced soil erosion, fuel 
3 
 
consumption and subsequent wear on equipment, while increasing water infiltration and 
retention in the soil (Hook, 1999). Increased use of conservation tillage results in a 
potential shift in weed communities (Locke et al, 2002).  Noted changes include 
increased perennial grasses and volunteer crops that act as weeds (Derksen, et al, 1993).  
With reduced inversion tillage practices, many producers have relied solely on 
postemergencence herbicides for weed control.  Conservation tillage and decreased 
tillage intensity by farmers has increased the occurrence of volunteer weeds from the 
previous year?s crop (Johnson III et al, 2000).  
 In Southeastern U.S., volunteer peanut is a reoccurring pest in cotton production.  
A ?volunteer peanut? is a peanut from the previous season(s) that survives the winter and 
emerges from the soil the following spring, competing with that crop for water, nutrients, 
and sunlight.  Volunteer peanut seed is created by harvest losses during the previous year.  
These losses may be caused by harvesting plants that are past maturity, harvesting when 
soils are exceptionally wet or dry, improperly operated harvest equipment, and/or weed 
roots that interfere with peanut digging and inverting.   
Peanut maturity and harvest.  Peanut maturity is difficult to measure because it is 
botanically considered indeterminate, with maturity often corresponding with summer 
rainfalls on non-irrigated fields (Windham, et al, 2010).  This creates a difficult scenario 
when attempting to estimate maturity of the crop.  The ?hull scrape? method is the 
current standard for producers as well as extension agents in determining the optimum 
time for inverting the crop.  Knowledge of pod maturity distributions leads producers to 
an estimated optimum digging time that can increase yield as well as market grades.  The 
hull scrape method can be accurate but there are also several limitations, including:  (1) 
4 
 
subjective judgment of observer, (2) labor and time of sampling and scrapping hulls, and 
(3) labor and time of categorizing hulls (Windham, et al, 2010).  These limitations push 
producers toward testing the earliest planted fields and then harvesting fields in the order 
of planting.  Peanut yield is dependent on many factors; digging one week prior or one 
week later than optimum maturity can result in great reductions in pod yield (Wright and 
Porter, 1991; Carley, et al, 2009).   Research conducted by Wright and Porter in 1990 
found that digging peanuts eight to eleven days before or after the optimum digging date 
reduced yields and value of crop.  Early peanut harvest reduced yields 15% while 
harvesting late reduced yields 6%.  The subsequent value of early harvested peanuts was 
reduced 21%, while digging late reduced value by 5% (Wright and Porter, 1991).     
Harvesting peanuts in dry and wet soils.  Peanut harvest occurs during hurricane 
season in the southeastern United States.  These tropical systems can bring large amounts 
of rain that interfere with peanut harvest season.  October is also historically the driest 
month of the year for the Southeast (AWIS, 2012).  Quantifying losses from harvesting 
peanuts can fluctuate significantly due to many external influences outside of peanut 
maturity and weather.  These can include, but are not limited to, peg strength differences 
in varieties (Thomas et al, 1983), soil structure, and precision of harvest equipment 
(Balkcom, et al, 2010).            
Peanut harvest losses.  Another reason for excessive peanut losses during harvest is the 
improper placement of harvest equipment while inverting.  When inverting peanut vines, 
the tractor operator must maintain the equipment precisely over the peanut rows.    By 
deviating from the rows, the blades or points of the inverter that are cutting the peanut 
taproot begin to dislodge peanuts from the vine causing high pod losses during harvest 
5 
 
(Balkcom et al, 2010).  Deviations from the center of the rows as small as 9 cm can 
reduce yields as much as 15%.  Deviations from the row center as much as 18 cm can 
reduce yields as much as 32% (Balkcom, et al, 2010).  If a farmer is harvesting 3920 kg 
ha-1 at $672/metric ton and is off 9 cm or 18 cm, they could potentially be losing $70 ha-1 
or $150 ha-1, respectfully.  Besides yield and profit, peanuts dislodged during digging 
remain in the ground and emerge the next spring.  Although the seed will be at various 
depths, they will germinate under a wide range of environmental circumstances (TCE, 
2007).   
Weed competition in peanuts.  Peanut yield loss from weed competition is dependent 
on factors such as soil moisture at harvest, density, species complex, length of 
competition, and weed growth habits (Everman et. al, 2008).  Because peanuts have a 
slow prostrate growth habit, broadleaf weeds can easily develop a canopy above crop 
foliage.  In weed competition studies, Everman et al, (2008) demonstrated that growers 
can suffer appreciable yield loss with poor weed management in the first eight weeks.  
Weed interference starting as early as three weeks after planting can decrease yields.  As 
the longevity of weed competition increases, the peanut yield decreases.   One way 
producers combat the slow canopy closure growth habits of peanut is to plant in twin-
rows.  This creates narrower row middles and allows the plants to close open row middles 
faster.  Brecke and Stephenson (2006) indicated that weeds such as Florida beggarweed 
[(Desmodium tortuosum (Schwartz) DC)] and sicklepod (Senna obtusifolia L.) had a 
higher rate of control in twin row over single row planting patterns.  Twin-row planting 
patterns have been shown to consistently increased yields (Wehtje, et al, 1984; Everman 
et. al, 2008).    
6 
 
Cotton weed management.  The importance of weed management for successful cotton 
production has been well-documented through yield increases via weed control (Askew 
and Wilcut, 1999; Morgan et al, 2001; Buchanan et al, 1980).  The goal of weed 
management is the reduction of weeds through planning and population assessments 
while using various management tools (Burnside, 1992).  There are several methods of 
controlling weeds including physical, cultural, mechanical, and chemical control. 
Management decisions that include selecting a vigorous variety, proper seedbed 
preparation, planting when soil is warm and moist, use of good seed, and proper soil 
fertility and pH can be employed so the cotton plants have the opportunity to compete 
against weeds (McWhorter and Abernathy, 1992).    
Farmers often start planting crops early in the spring to take advantage of seasonal 
rainfall patterns as well as plant all their acreage in a timely manner.  Many times 
conditions are not conducive for cotton to grow vigorously because the soil is cold and 
wet.  If the crop struggles to grow then weeds can flourish.  In early spring, large 
temperature variations can occur from day to day in the cotton belt.  A common rule that 
southeastern U.S. producers use specifies that the soil temperature at the 20 cm depth 
should average 15.5 degrees C for a 10-day period before planting is initiated (Mauney 
and Stewart, 1986).  Fields can be located in distant proximity to primary infrastructure 
making it very difficult to be timely with herbicide applications. Weed control methods 
have changed drastically over the last century.  Hand tools and animal-powered 
cultivators were the 1900?s cotton farmer?s primary tools for managing weeds before the 
development of tractors, and herbicides (McWhorter and Abernathy, 1992).  The goal of 
7 
 
cultivation was to eliminate and prevent the emergence or growth of weeds and grass that 
reduced yields and grades (Sturkie and Williamson, 1951) without injuring the crop.   
In the last 15 years, cultivation decreased and gave way to conservation tillage 
and herbicides mainly due to the introduction of glyphosate resistant crops in 1997 
(Faircloth et al, 2001).  Glyphosate was initially utilized in controlling perennial weeds 
on ditch banks, right of ways, and fallow fields.  However, because of the absence of 
resistance by crops, its uses in agriculture were limited.  The increase of conservation 
tillage and no-till practices along with herbicide-tolerant crops significantly increased the 
utility and use of glyphosate (Nandula, 2010).     
 Along with glyphosate, the herbicide glufosinate has aided the transition into 
conservation tillage by being a nonselective herbicide incorporated into resistant crops.  
Glufosinate has also become a tool for farmers in battle against glyphosate resistant 
weeds such as Palmer amaranth (Amaranthus palmeri S. Wats.).  Due to the ease of using 
glyphosate and its broad spectrum of weed control, farmers began to grow cotton in 
monoculture systems while relying on multiple applications of glyphosate exclusively for 
weed control (Culpepper et al, 2006; Gardner et al, 2006).  This dependence on a single 
weed control system ultimately led to the development of glyphosate resistant weeds.  
Glufosinate resistant cotton was registered in 2004, which can be effective against 
glyphosate resistant weeds because of its ability to inhibit glutamine synthetase which 
leads to a buildup of ammonia in leaf tissues causing necrosis and death of leaves 
(Gardner et. al, 2006).  
 
8 
 
Volunteer peanut harboring effect on cotton production.  Volunteer peanut harbors 
pests like the green stink bug (Nezara viridula L.) and the brown stink bug [Euschistus 
servus (Say)], that are detrimental to cotton production.  Green and brown stink bugs that 
develop will often migrate to adjacent fields and feed on cotton bolls (Tillman, et al, 
2009).  In 2009, Smith and Davis (not published) investigated stink-bug control in cotton 
by planting four rows of cotton between adjacent rows of peanuts.  This was to create an 
artificially high number of stink-bug pests to rate the efficacy of control methods at 
different application timings.  At least 600% increase in seed cotton yields was realized 
by applying insecticide combinations for stink bug control.  This indicated that, while 
stink bugs are not a major pest in peanut production,  the crop can harbor damaging pests 
of cotton.   
Controlling volunteer peanut in cotton. There has been limited research on 
controlling volunteer peanuts due to adequate control through other means mentioned 
earlier such as inversion tillage.  York et al (1994) reported that sequential applications of 
glyphosate were better than a single application for volunteer peanut control.  Control 
with single applications of glyphosate also improved with increased rates.  Regardless of 
the herbicide rate, volunteer peanut control improved when the peanut had a 20-30 cm 
diameter due to increased herbicide interception.  York et al also showed that at least 
80% control of volunteer peanut could be using glyphosate with single applications at 
high rates or sequential treatments.  One limiting characteristic of this study was the use 
of spring planted peanut instead of volunteer peanut.  William Birdsong, Alabama 
Cooperative Extension System Cotton Specialist for Southeastern Alabama, (personal 
contact, 2011) says many farmers have expressed the difficulty of controlling volunteer 
9 
 
peanuts with cotton herbicides, whereas glyphosate drift will kill spring planted peanut 
easily.  Moisture stressed peanut is also more difficult to kill, which may be why 
sequential applications are preferred by producers (York, et al, 1994).  The objective of 
this study was to determine the effectiveness of glyphosate (RoundUp Ready? system) 
and glufosinate (LibertyLink? system) for controlling volunteer peanut in cotton in south 
Alabama. 
Materials and Methods 
 
 An experiment was implemented to determine effects of glyphosate and 
glufosinate on volunteer peanuts.  Field studies were conducted in 2010 at the Gulf Coast 
Research and Extension Center (GCREC) in Fairhope, AL., a Malbis sandy loam soil 
(fine-loamy, siliceous, subactive, thermic Plinthic Paleudults), and at the Wiregrass 
Research and Extension Center, Headland (WREC), AL, a Dothan sandy loam (fine-
loamy, kaolinitic, thermic Plinthic Kandiudults).    
Both experiment sites were planted to peanut the season prior to cotton (2009). At 
WREC, the peanut crop was harvested in excessive soil moisture while the peanut crop at 
the GCREC was not harvest but tilled into the soil.  The cotton varieties ?DPL 0935 
BGIIRF? and ?FM 1845 BGIILL? were planted at both sites at the rate of 8.2 seed m-1 to 
the depth of 2.54 cm.  Plot size was four rows spaced 92 cm apart and 7.62 m in length.  
Experimental design at both locations was a randomized complete block with treatments 
replicated four times.   
Cotton was planted on May 18, 2010 at GCREC and on May 28, 2010 at WREC.  
At planting, a uniform broadcast application of pendimethalin (Prowl H2O?, BASF 
Corporation, Research Triangle Park, NC) at 0.84 kg ha-1 + fomesafen (Reflex?, 
10 
 
Syngenta Crop Protection, Inc., Greensboro, NC) at 0.105 kg ha-1 was applied at both 
locations.   
 Treatments included glyphosate (RoundUp Power Max?, Monsanto Company, St. 
Louis, MO.) at 1.12 kg ha-1 & glufosinate (Ignite?, Bayer CropScience, Research 
Triangle Park) at 0.47 kg ha-1 applied at cotton?s 2-leaf, 4-leaf, or 2+4-leaf alone or 
followed by an application of trifloxysulfuron-sodium (Envoke?, Syngenta Crop 
Protection, Inc., Greensboro, NC) at 0.005 kg ha-1 at the 8-leaf stage.  Initial applications 
of glyphosate or glufosinate included S-metolachlor (Dual Magnum?, Syngenta Crop 
Protection, Inc., Greensboro, NC) at 0.14 kg ha-1.  All plots received prometryn  
(Caparol?, Syngenta Crop Protection, Inc., Greensboro, NC) at 1.12 kg ha-1 + 
monosodium acid methanearsonate (MSMA?, Drexel Chemical Company, Memphis, 
TN) at 2.24 kg ha-1 as a post-directed spray to cotton.  Non-treated and weed free checks 
were included for comparison with non-treated excluded from statistical analysis.   
Glyphosate was pre-mixed with a non-ionic surfactant while a non-ionic surfactant (Top 
Surf?, Winfield Solutions, LLC. St. Paul, MN.) was added to glufosinate and 
trifloxysulfuron-sodium at 0.25% v/v.  Herbicide applications were made with a 
pressurized CO2 backpack sprayer delivering 145 L/ha with 11004 flat fan nozzle 
(TeeJet?, Spraying Systems Co., Glendale Heights, IL.).    
 Weed control ratings were visually estimated at 7 days after treatment (DAT) of 
2-leaf, 10 DAT of 4-leaf, and 31 DAT of 8-leaf applications on a 0 to 100% scale with 0 
being no control and 100 being complete control.  In addition to peanut, grass species 
were identified and rated at both locations.  The center two rows of cotton were harvested 
from each plot on September 23, 2010 at GCREC and October 21, 2010 at WREC with 
11 
 
percent lint determined by gin turn-out of plot samples at GCREC and by a constant 38% 
gin turn-out at WREC.    
 Data are presented by location due to significant main effects for yield and peanut 
control.  Transformation of data did not improve homogeneity of variance.  Yield data 
and weed control ratings were subjected to ANOVA (P=0.05) with PROC GLM in SAS 
(SAS version 9.2, SAS Institute Inc., Cary, NC).     
 
Results and Discussion 
 Data analysis indicated a significant location*treatment interaction; therefore, 
control and yield data are presented separately by location.   
Weed control. In the first volunteer peanut control rating (Figure 1) at the Wiregrass 
Research and Extension Center (WREC), there was no significant difference between any 
of the 2-leaf treatments.  This is also true with the first grass complex control rating 
(Figure 2). The grass complex consisted of southern crabgrass (Digitaria ciliaris Retz.), 
bermudagrass (Cynodon dactylon L.), and broadleaf signalgrass (Urochloa platyphylla 
Munro ex C. Wright).  There was exceptional control seen on these grasses early.  This 
was likely due to control by the burn down herbicide application.  Although 
pendimethalin was applied as a pre-emergent grass herbicide, escapes began to come 
through by the 4-leaf rating. This is evident in the 2-leaf and 4-leaf treatments where late 
season ratings were extremely low for grass control.   
Following the second rating of volunteer peanut control at the WREC, 10 days 
after the 4-leaf treatment (Figure 3), the 2-leaf application alone decreases in percent 
control and is significantly lower than all other treatments except the 4-leaf treatment.  
12 
 
This is most likely due to the late emergence of volunteer peanut.  The 4-leaf treatment 
alone is significantly lower most likely due to the volunteer peanut having a larger size 
before applications were made creating an environment that makes weed control difficult.  
However, York, et al, (1994) showed a higher percentage of control with larger peanut 
due to increase in herbicide interception.  In this study, volunteer peanut was used 
whereas York et al used spring planted peanuts.  Although 4-leaf applications had a low 
% control, by adding an 8-leaf application of trifloxysulfuron-sodium, an increase in 
volunteer peanut control was achieved.  The % control of grasses for the 4-leaf 
application was significantly less than the 2-leaf or the 2+4-leaf applications most likely 
due to larger grass size at application timing (Figure 4).   
The last rating showed the 2-leaf and 4-leaf applications alone significantly lower 
volunteer peanut control than the other treatments (Figure 5).  Although there was not a 
significant difference in grass control %, the same pattern was also seen with numerical 
differences (Figure 6).  The best control was seen in the 2+4+8-leaf and 2+8-leaf 
treatments.  However, this was still only an 80%-85% control.  There was no significant 
difference in control of volunteer peanuts with glyphosate or glufosinate at the first, 
second, or final ratings.  However, there was a noticeable difference in grass control 
between technologies (Figure 7).     
At the Gulf Coast Research and Extension Center (GCREC), better overall 
volunteer peanut control across all treatments was obtained over treatments at WREC.  
Several influencing factors could potentially include precipitation timing, early 
emergence of volunteer peanuts, and/or a shading effect from the cotton.  The 2-leaf only 
treatment was significantly lower than all other treatments at the late rating (Figure 8).  
13 
 
This was most likely due to emergence of volunteer peanut after the first application.  
The weed free treatment, 4-leaf treatment, and the 2+4-leaf treatment had significantly 
higher control of volunteer peanut than the 2+4+8 and the 4+8 treatments.  However, the 
2+4+8-leaf and 4+8-leaf treatments had comparable control to the 2+4, 2+8, and weed 
free treatments in grass control while the 4-leaf treatment was significantly lower than the 
2+4, 2+4+8, and weed free treatments (Figure 9).  At WREC treatments with the 8-leaf 
application of trifloxysulfuron-sodium tended to increase late control of volunteer peanut, 
whereas at GCREC, those treatments were lower in control ratings.  It is unclear what 
factors contributed to these location differences and more research is necessary to 
understand to what degree trifloxysulfuron efficacy is affected by environmental 
variability.   
 There was a similar trend with treatments at GCREC for the first ratings of 
volunteer peanuts and grass control as observed at WREC.  For weed control at the 2-leaf 
application stage, volunteer peanut control was statistically the same for all treatments 
and lower than the weed free treatment (Figure 10).  All 2-leaf applications for grass 
control were very high (Figure 11).   
 At the 4-leaf rating, the 2-leaf only treatment was significantly lower in volunteer 
peanut and grass control (Figure 12, Figure 13).  This was more than likely due to the late 
emergence of grass or volunteer peanut that was not controlled by an early application 
alone.  There was no significant difference in 2+4, 4-leaf, 4+8, or weed free treatments on 
volunteer peanut control.  The 2-leaf treatment had significantly lower grass control than 
the 2+4, 2+4+8, and the weed free treatments.   
14 
 
There was also a significant difference in control of peanuts when comparing 
glufosinate and glyphosate at GCREC (Figure 14).  With the first rating, there was no 
significant difference in glyphosate and glufosinate control of volunteer peanuts.  By the 
second rating, 10 days after the 4-leaf application, glyphosate began showing a 
significant increase in % control of volunteer peanut and continued that trend until the 
last rating.   
This same trend was seen in grass control at GCREC (Figure 15) with glyphosate 
being significantly better than glufosinate.  High control ratings with glufosinate at the 
first rating for grasses could be attributed to contact injury caused by glufosinate on plant 
tissue.  However, glufosinate does not translocate and kill the roots to provide complete 
control.   Over time, glyphosate applications provided better grass control than 
glufosinate.   
Cotton yield.  At the Wiregrass Research and Extension Center (WREC) in Headland, 
AL, the 2+4+8-leaf application and the 2+8-leaf application treatments had significantly 
higher yields than the no control, 2-leaf, 4-leaf, and 2+4-leaf treatments (Figure 16). 
However, this is not attributed to significantly better volunteer peanut (Figure 5) or grass 
control (Figure 6) at season end.  There was a noted difference in yields between 
technologies with glyphosate resistant hybrids having significantly higher yields than 
glufosinate resistant hybrids at WREC (Figure 17). 
At the Gulf Coast Research and Extension Center, Fairhope, AL there was also a 
significant difference seen in yield (Figure 18).  However, unlike Headland where two 
treatments were significantly different, Fairhope had five treatments among the top in 
yields.  The 2-leaf treatment, 2+4-leaf treatment and the 4-leaf treatments were all 
15 
 
significantly higher than the 2+8-leaf and the no control treatments.  One possible 
explanation for this is the amount of rainfall and timing of rainfall for Fairhope.  The 
precipitation increased in August and September as bolls were increasing in size as well 
as maturing.  During the months of August and September, Fairhope received a total of 
40.56 cm of rainfall.  This was not the case in Headland as they remained dry receiving a 
total of only 14.20 cm in both months (AWIS, 2012).    
 At both sites it was visible that one application of either glyphosate or glufosinate 
was not enough to completely control volunteer peanuts or various grasses.  Where 
multiple applications were applied better control was generally observed.   Glyphosate 
seemed to have better control on grasses and volunteer peanut than glufosinate.  Along 
with better control and technologies came higher yields.  At WREC, the addition of 
trifloxysulfuron-sodium increased the control of volunteer peanut, whereas at  GCREC 
that data was not found true.  Although an increase in volunteer peanut control did not 
always equal an increase in cotton yields, the no control treatments were overtaken by 
volunteers as well as other weeds producing very little yield.  Single applications of 
herbicides increased weed control over no applications while multiple applications of 
herbicides consistently increased weed control and yields over single applications.     
 In this study, no application timing or technology provided consistent superior 
performance in volunteer peanut control.  More research is needed in timing of volunteer 
peanut emergence and competition level with cotton crop.  This research is necessary to 
determine how many applications are needed to get the highest percent control of 
volunteer peanut and how volunteer peanut reduces cotton yields through direct 
competition.     
 
16 
 
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19 
 
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Peanut Sci. 21:40-43. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
20 
 
 Figure 1. Control of volunteer peanut following postemergence applications of glyphosate and glufosinate 
herbicides at cotton?s 2-leaf stage at Wiregrass Research and Extension Center, Headland, AL.a b 
 
a Ratings reflect control 7 DAT of 2-leaf cotton stage. Applications for 4-leaf and 4+8-leaf   
not applied at time of rating. 
b All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
B 
B 
B B 
c c 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
21 
 
Figure 2.  Control of various grass species following postemergence herbicide at cotton?s 2-leaf stage at 
Wiregrass Research and Extension Center, Headland, AL.a b  
 
a Ratings reflect control 7 DAT of 2-leaf cotton stage. Applications of 4-leaf and 4+8-leaf   
not applied at time of rating. 
b All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
B A A A 
C C 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
22 
 
Figure 3. Control of volunteer peanut following postemergence applications of glyphosate and glufosinate 
herbicides at cotton?s 4-leaf stage at Wiregrass Research and Extension Center, Headland, AL.a b  
 
a Ratings reflect control 10 DAT of 4-leaf cotton. 
b All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
D 
CD 
AB 
B 
D 
BC 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
ntro
l 
Postemergence Application Timingc 
23 
 
Figure 4. Control of various grass species following postemergence applications of glyphosate and 
glufosinate herbicides at cotton?s 4-leaf stage at Wiregrass Research and Extension Center, Headland, AL.a 
 
a Ratings reflect control 10 DAT of 4-leaf cotton. 
b All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
AB 
AB 
ABC BC 
C 
AB 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
24 
 
Figure 5. Control of volunteer peanut following postemergence herbicide at cotton?s 8-leaf stage at 
Wiregrass Research and Extension Center, Headland, AL.a 
 
a Ratings reflect control 31 DAT of 8-leaf cotton.   
b All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
C 
B 
B B 
C 
B 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
ntro
l 
Postemergence Application Timingc 
25 
 
Figure 6. Control of various grass species following postemergence herbicide at cotton?s 8-leaf stage at 
Wiregrass Research and Extension Center, Headland, AL.a 
 
a Ratings reflect control 31 DAT of 8-leaf cotton.   
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
B 
AB AB AB 
B 
AB 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
26 
 
Figure 7. Comparing glyphosate and glufosinate control of various grass species at Wiregrass Research and 
Extension Center, Headland, AL. a  
   
aAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
bEither 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
A 
A A 
A 
B 
B 
0
10
20
30
40
50
60
70
80
90
100
2-leaf 2+4-leaf 2+ 4+8-leaf
% 
CO
NT
RO
L 
Postemergence Application Timingb 
Glyphosate
Glufosinate
27 
 
Figure 8. Control of volunteer peanut following postemergence herbicide at cotton?s 8-leaf stage at Gulf 
Coast Research and Extension Center, Fairhope, AL.a 
 
a. Ratings reflect control 31 DAT of 8-leaf cotton.   
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
D 
AB 
C BC 
AB 
C 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+ 4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
28 
 
Figure 9. Control of various grass species following postemergence herbicide at cotton?s 8-leaf stage at 
Gulf Coast Research and Extension Center, Fairhope, AL.a 
 
aRatings reflect control 31 DAT of 8-leaf cotton.   
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
BC 
A AB 
ABC 
C 
ABC 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
29 
 
 Figure 10. Control of volunteer peanut following postemergence applications of glyphosate and glufosinate 
herbicides at cotton?s 2-leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL.a 
 
a Ratings reflect control 7 DAT of 2-leaf cotton stage. Applications of 4-leaf and 4+8-leaf   
not applied at time of rating. 
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
B 
B 
B 
B 
C C 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+ 4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
30 
 
Figure 11. Control of various grass species following postemergence herbicide at cotton?s 2-leaf stage at 
Gulf Coast Research and Extension Center, Fairhope, AL.a 
 
a Ratings reflect control 7 DAT of 2-leaf cotton stage. Applications of 4-leaf and 4+8-leaf not applied at 
time of rating. 
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
B A A A 
C C 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timing 
31 
 
Figure 12. Control of volunteer peanut following postemergence applications of glyphosate and glufosinate 
  herbicides at cotton?s 4-leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL.a 
 
a Ratings reflect control 10 DAT of 4-leaf cotton. 
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
C 
AB B B AB AB 
A 
0
10
20
30
40
50
60
70
80
90
100
2 LEAF 2+ 4 LEAF 2+4+8 LEAF 2+8 LEAF 4 LEAF 4+8 LEAF WEED FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
32 
 
Figure 13.  Control of various grass species following postemergence applications of glyphosate and 
glufosinate herbicides at cotton?s 4-leaf stage at Gulf Coast Research and Extension Center, Fairhope, AL.a 
b 
 
 
a Ratings reflect control 10 DAT of 4-leaf cotton. 
bAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
c Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
 
B 
A 
A 
AB AB 
AB 
A 
75
80
85
90
95
100
2 LEAF 2+4 LEAF 2+4+8
LEAF
2+5 LEAF 4 LEAF 4+8 LEAF WEED
FREE
% 
Co
nt
ro
l 
Postemergence Application Timingc 
33 
 
Figure 14. Comparing glyphosate and glufosinate control of volunteer peanut at Gulf Coast Research and 
Extension Center, Fairhope, ALa  
 
aAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
b Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
cRatings reflect control 31 DAT of 8-leaf cotton.   
 
 
 
 
 
 
 
 
 
 
 
 
A 
A A 
A 
B 
B 
68
70
72
74
76
78
80
82
84
86
88
2 Leaf 2+4-leaf 2+4+8-leaf
% 
Co
nt
ro
l 
Postemergence Application Timingb c 
LL
RR
34 
 
Figure 15. Comparing glyphosate and glufosinate control of various grass species at Gulf Coast Research 
and Extension Center, Fairhope, AL a  
 
 
 
 
aAll treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47 kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
b Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2-, 4-, or 2+ 4-leaf.  
Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1 at the cotton?s 8-leaf stage.   
cRatings reflect control 31 DAT of 8-leaf cotton.   
 
 
 
 
 
 
 
 
 
 
 
A A A A 
B 
B 
75
80
85
90
95
100
2-leaf 2+4-leaf 2+4+8-leaf
% 
CO
NT
RO
L 
Postemergence Application Timingb c 
RR
LL
35 
 
 
Figure 16.  Cotton lint yield (kg ha-1) at Wiregrass Research and Extension Center, Headland, AL.a,b,c 
 
a All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47lbs kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
b Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2, 4, or 2& 4-leaf . 
c Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1  at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
 
 
 
 
 
C C 
A 
AB 
C 
BC BC 
D 
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
2 LEAF 2+4 LEAF 2+4+8
LEAF
2+8 LEAF 4 LEAF 4+8 LEAF WEED
FREE
NONE
Lin
t Y
iel
d k
g h
a-1
 
Treatment Application Timing 
36 
 
Figure 17.  Comparison of RoundUp Ready (RR) yield vs. LibertyLink (LL) at Wiregrass Research and 
Extension Center, Headland, AL. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
A 
B 
0
200
400
600
800
1000
RR LL
Lin
t Y
iel
d k
g/h
a-1
 
Herbicide Resistant Technology in Cotton  
37 
 
Figure 18.  Cotton lint yield (kg ha-1) at Gulf Coast Research and Extension Center, Fairhope, AL.a,b,c   
a All treatments  received 1.8525 kg a.i. ha-1 of pendimethalin + 0.105 kg a.i. ha-1 of fomesafen as a pre-
emergent and 2.47lbs kg a.i. ha-1 of  prometryn + 4.94 kg a.i. ha-1 of MSMA as post-directed spray.   
b Either 2.47 kg a.i. ha-1 glyphosate or 1.0375 kg a.i. ha-1 glufosinate was sprayed at 2, 4, or 2& 4-leaf . 
c Trifloxysulfuron-sodium was applied at 0.011362 kg a.i. ha-1  at the cotton?s 8-leaf stage.   
 
 
 
 
 
 
AB AB 
BC C 
A ABC ABC 
D 
0
100
200
300
400
500
600
700
800
900
2 LEAF 2+4 LEAF 2+4+8
LEAF
2+8 LEAF 4 LEAF 4+8 LEAF WEED
FREE
NONE
Lin
t Y
iel
d k
g h
a-1
 
Postemergence Application Timing