University of FloridaSolutions for Your Life

Download PDF
Publication #SS-AGR-04

Weed Management in Cotton 1

J. A. Ferrell, G. E. MacDonald, and R. Leon2

Successful weed control is essential for economical cotton production in Florida. Weeds compete with cotton for moisture, nutrients, and light. The greatest competition usually occurs early in the growing season. Late-season weeds, while not as competitive as early-season weeds, may interfere with insecticide applications and may cause harvesting difficulties.

Crop Rotations

Crop rotations are an important part of a good cotton weed control program. Certain weeds, especially nutsedges, may be less difficult to control in a preceding crop such as peanut. Other benefits of crop rotation may include reduction in insect, disease, and nematode problems both in cotton and succeeding crops.

Cultivation

Cultivation can be utilized if effective weed control is not achieved with herbicides. However, if weeds have been controlled with herbicides, there is generally little benefit from cultivation. If cultivation is needed, avoid throwing soil around small cotton plants to minimize disease problems.

Herbicides

Herbicides are the most effective means for controlling weeds in cotton. To be effective, however, herbicides need to be matched with the weed problem. Therefore, before purchasing a herbicide, you should first know your weed problem. Once this has been determined, Tables 4, 5, and 6 can be helpful in choosing the herbicide that is best suited for your particular situation.

Preplant and/or preemergence applications are important for ensuring that the cotton has the initial competitive advantage over the weeds. Once this is achieved, then postemergence directed applications can be utilized to extend the weed control throughout the season. The herbicides listed in Table 1 are those that have performed well in trials conducted at the West Florida Research and Education Center (Jay), the Gainesville area, and the North Florida Research and Education Center (Quincy and Marianna).

Herbicide Application

Calibrate accurately since rates too high may injure crop and rates too low may not provide adequate weed control. This is especially critical with banded applications, which often are utilized in cotton. In addition, all label instructions and precautions should be followed carefully. Be sure that the application is properly timed in relation to the stage of growth of both crops and weeds. Do not allow spray to drift to sensitive crops. Store herbicides behind locked doors in original containers with intact labels, and separated from seed, fertilizer, and other pesticides.

It is very important to use a clean spray system prior to spraying any crop. After each use, rinse the system thoroughly and use a tank cleaner solution to ensure that no herbicide residue remains. See SS-AGR-102, Calibration of Herbicide Applicators (http://edis.ifas.ufl.edu/wg013) for more information on cleaning spray equipment.

Hooded Sprayers

Use of nonselective herbicides applied with a hooded sprayer may be desirable for row middles. Care should be taken to avoid contact with the crop. A residual-type herbicide may be used and will extend weed control, which may delay layby herbicide applications.

Herbicide-Tolerant Cotton

Liberty Link

Liberty Link cotton is a technology that allows the application of Liberty herbicide, glufosinate, over the top of green foliage. Glufosinate is completely different from glyphosate. Glufosinate inhibits glutamine synthase enzymes, and toxic levels of ammonia quickly accumulate in plant tissues. Since this process is radically different from Roundup Ready technology, applications of Liberty to Roundup Ready Cotton will result in death of the crop. Likewise, glyphosate cannot be safely applied to Liberty Link cotton.

Application Timing

The Liberty Link cotton allows an effective broadleaf herbicide to be applied postemergence over the top of cotton. Liberty 280 can be applied to Liberty Link cotton from emergence until early bloom. A spray volume of 15 gallons/A or more with an operating pressure of 40 psi or greater is recommended for use with flat fan nozzles. It may be applied postemergence without visible crop injury, yield reduction, or delay in maturity. No more than 80 oz/A can be made per growing season. Liberty Link cotton cannot legally be grown south of Tampa, Florida (Route 60).

Herbicide Program

Liberty has no soil residual activity and will only control weeds that have emerged at time of application. A traditional preplant-incorporated or preemergence herbicide, such as Prowl, Treflan, or Cotoran may be needed to enhance the level of weed management. The suggested use rate for Liberty 280 is 23–43 oz/A, depending on weed size and species. No more than 43 oz per application, or 87 oz per season, may be applied to cotton. See the label for weed size and rate information. Liberty may be applied from emergence to early bloom. Cultivation should be delayed 5 to 7 days following application. Liberty is rainfast in 4 hours. Therefore, if rain is imminent, applications of Liberty should be delayed. Ammonium sulfate at 3 lb/A has been shown to enhance the activity of Liberty (Table 2).

Liberty provides fair to good grass activity, so applications should target grasses that are 3" to 6" in height. Postemergence grass control can be supplemented by several postemergence grass herbicides, but these should not be tank-mixed with Liberty 280. For other difficult to control weeds, such as pigweeds, Liberty may be tank-mixed with Staple.

* NOTE: Liberty Link cotton use is limited to the area located north of Tampa (Florida Route 60). Also, Liberty will kill Roundup Ready Cotton, and vice versa.

Rotation Restrictions

Liberty requires a 120-day restriction for all rotational crops, except for wheat, barley, sorghum, and other crops contained on the label.

Roundup Ready Cotton

Roundup Ready cotton has been genetically modified to tolerate glyphosate. There are several products containing glyphosate, but all are not labeled for use on Roundup Ready cotton. Consult your county agent or the labels; use only those glyphosate products that are labeled for use on Roundup Ready cotton. Glyphosate provides control of broadleaf weeds, grasses, and nutsedges. It must be applied at the proper timing to avoid crop injury (see Application Timing).

Application Timing

Proper glyphosate application timing is essential to avoid injury in Roundup Ready cotton. Glyphosate can be applied over the top of Roundup Ready cotton anytime from cotton emergence until the fourth true-leaf stage. Applications of glyphosate over the top of cotton are prohibited after the cotton exceeds the four-leaf stage, except in salvage situations. These late (after 4 leaf) overtop applications will result in bloom abortion and loss of yield. For Roundup Ready Flex cotton, glyphosate can be applied from cotton emergence until 7 days prior to harvest.

Roundup can be applied post-directed until layby. Consult the label for the suggested use rate. Glyphosate can be applied twice over the top of Roundup Ready cotton when the following criteria are met. The two applications must be at least 10 days apart, there must be two nodes of new growth between the applications, and the second application must be made before cotton exceeds the four-leaf stage. Therefore, if you are going to use two over-the-top applications, the first must occur prior to the 2nd true leaf, and the second application during the 4th true leaf stage.

Directed glyphosate applications must minimize contact with the cotton plant when applied after the four-leaf stage. Glyphosate can be applied late season after 20% of the bolls have cracked. At least 7 days between application and harvest are necessary.

Herbicide Program

Preemergence - An advantage to the Roundup Ready system is the option to eliminate preemergence herbicides. Early season weed competition should be considered when determining the weed management program. This competition may be avoided by an early glyphosate application (i.e., one-leaf stage). If a preemergence herbicide is used, the glyphosate application can be delayed until the three- or four-leaf stage. Consideration should be given to total cotton acreage, weed spectrum, and the acceptable risk level when weather delays postemergence applications. Preemergence herbicides are a type of insurance policy and often maintain a grower's peace of mind. A soil-applied preemergence herbicide should be utilized in the program to provide early-season control of annual grasses and Florida pusley (Table 3).

Tank Mixes

Glyphosate does not provide any soil or residual activity. Therefore, tank mixtures can be utilized for broad spectrum weed control and/or residual activity. A tank mix of Staple and glyphosate improves control of hemp sesbania, spreading dayflower, and morningglory species (all except tall). A premix of this combination is available under the trade name Staple Plus.

Tables 4, 5, and 6 can be helpful in choosing the herbicide that is best suited for your particular situation.

Tables

Table 1. 

Weed management in non-transgenic cotton

Trade Name and Broadcast Rate/Acre of Commercial Product

Common Name and Broadcast Rate/Acre of Active Ingredient

Remarks

BURNDOWN HERBICIDES

Glyphosate (several)

glyphosate

(0.5–1.0 lb)

Use higher rate for larger weeds or heavy infestations. Use a 0.25% v/v surfactant with some formulations. Apply after weed emergence up to 3–7 days before planting. Touchdown must be applied at least 35 days before planting. If tillage is intended after treatment, wait at least 3 days. Rainfall within 6 hours after application may decrease control.

glyphosate

(several)

+

2,4-D

(0.5–1 pt)

glyphosate

+

2,4-D

The addition of 2,4-D will increase control of cutleaf eveningprimrose, wild radish, horseweed, and other winter annuals. Cotton planting must be delayed for a minimum of 30 days after 2,4-D application.

glyphosate

(several)

+

Clarity

(8 fl oz)

glyphosate

(0.5–1 lb)

+

dicamba

Following application of dicamba AND a minimum of 1 in. of rainfall, a waiting period of at least 21 days is required before planting. Dicamba can be applied alone with little to no effect on the small grain cover crop.

Dicamba is less effective than 2,4-D on primrose.

glyphosate

(several)

+

Harmony Extra 50 SG

0.75 oz/A

or

Harmony Extra 75 WDG

0.5 oz/A

glyphosate + thifensulfuron + tribenuron

Apply at least 14 days prior to planting for control of chickweed, henbit, and wild radish.

glyphosate

(several)

+

Valor

(1–2 oz)

glyphosate

+

flumioxazin

The addition of Valor will increase control of cutleaf eveningprimrose and wild radish. A minimum of 14 days and the accumulation 1” of water must occur before planting cotton if 1 oz of Valor is used. If using 2 oz, delay planting for 21 days. Valor will give approximately 6 weeks of residual control of small seeded weeds (pigweeds, Florida pusley, smallflower morningglory) if adequate soil contact occurs. For resistance managment, do not use Reflex preplant or Valor at layby if Valor is applied at burndown.

Gramoxone SL

(2.5–4 pt)

Firestorm, Parazone, others

(1.7–2.7 pt)

paraquat

Apply prior to, during, or after planting but before crop emergence. Should be applied in at least 10 gal spray solution per acre. May be mixed with 2,4-D to improve activity on some broadleaf weeds. See information below for specifics on 2,4-D.

Paraquat (several)

+

Direx 4L

(1.6 pt)

paraquat

+

diuron

Do not apply on sand or loamy sand soil. Higher rates of diuron may be used on heavier soils; see labels. Apply diuron 15 to 45 days ahead of planting. If Cotoran is applied preemergence, reduce rate to account for residual activity of diuron.

2,4-D ester or amine

(various formulations)

2,4-D

(0.37–1.0 lb)

The most consistent and effective burndown program for winter weeds in Florida would be a 2,4-D application in February when weeds are small and herbicide coverage is adequate followed by glyphosate or paraquat at or near planting.

Primrose: Apply 0.37 to 0.5 lb ai/A.

Radish: Apply 0.5 to 0.75 lb ai/A.

Horseweed: Apply 0.75 to 1.0 lb ai/A.

Plant back restriction for 2,4-D is often 30 days, but see specific product label to determine cotton plant back interval.

PREPLANT

Treflan/various

(1–2 pt)

or

Pendimethalin 3.3 EC

(1.2–1.8 pt)

or

Prowl H2O 3.8 AS

(2 pt)

trifluralin

pendimethalin

Good control of annual grasses and certain broadleaf weeds. Poor control of cocklebur, sicklepod (coffeeweed), morningglory, and ragweed. No nutsedge control. Incorporate thoroughly according to label directions. The spectrum of weeds controlled is similar for each of these herbicides. Treflan must be incorporated with tillage or irrigation within 24 hours of application. Prowl H20 will persist on the soil surface much longer than Prowl 3.3EC or Treflan.

Solicam

(1.25 lb)

norflurazon

May be applied tank-mixed with Treflan or Prowl and can give good to excellent control of prickly sida with enhanced control of deep germinating weeds such as cocklebur or morningglory. Control may be superior to PRE applications when applied PPI if dry conditions predominate. If used PPI, do not exceed 2.5 lb of Solicam total per season in both PPI and PRE applications. See label for rotation restrictions.

PREEMERGENCE

Cotoran 4L or Flo-Met 4L

(2.0–3.2 pt)

fluometuron

Apply after planting and before emergence of the crop or weeds. Good control of annual grass and broadleaf weeds. Use low rate on sandy soils.

Direx DF

(1.0–1.5 lb)

or

Direx 4L

(1.6–2.4 pt)

diuron

Similar to fluometuron but less effective on large-seeded broadleaf weeds.

Reflex 2L

1 pt/A

fomesafen

Particularly useful for fields infested with glyphosate-resistant Palmer amaranth. Can injure cotton if soils have low organic matter content or if heavy rainfall is received during cotton emergence. For resistance managment, make only one application of Reflex or Valor per crop per year.

Solicam

(1.25–2.5 lb)

norflurazon

Apply after planting and before emergence of crop or weeds. Good control of annual grasses and many broadleaf weeds. May suppress nutsedge. May cause problems with rotational crops such as cereal grains and corn. Consult label for specific restrictions. Solicam will not adequately control Palmer amaranth.

Staple LX

1.7–2.1 oz

pyrithiobac

Do not apply on soils with less than 0.5% organic matter. Can tank-mix with Diuron, Cotoran, or Prowl. Palmer amaranth biotypes resistant to Staple are present in Florida.

POSTEMERGENCE

Dual Magnum

(1–1.33 pt)

S-metolachlor

DO NOT APPLY PREEMERGENCE OR SEVERE COTTON INJURY WILL OCCUR. To control tropical spiderwort, apply at the 4-leaf stage of cotton. Dual will only control weeds that have NOT emerged. To increase effectiveness, efforts should be made to maximize soil contact by spray solution. Metolachlor-containing products will often result in slight cotton leaf damage, especially if applied during hot humid conditions or when dew covers the leaf. This injury will persist approximately 7 days and yield will not be affected. Cinch and Dual II Magnum are not registered for use in cotton.

Envoke

(0.1 oz)

trifloxysulfuron

Excellent control of sicklepod, morningglory (except smallflower morningglory) and nutsedges. Apply with nonionic surfactant (0.25% v/v) from the cotton 5-leaf stage until 60 days before harvest. DO NOT apply prior to 5-leaf stage or unacceptable cotton injury will result. Do not tank-mix with other herbicides, oil adjuvants, fertilizers, or insecticides. Do not apply over the top of stripper-type cottons. Do not apply more than 0.4 oz/A/yr.

Fusilade DX

(6–12 oz)

fluazifop-butyl

Apply for control of most annual and perennial grasses before they exceed 4" in height. See label for specific rates and weeds. Add crop oil concentrate (1 gal) or nonionic surfactant (2 pts) per 100 gal spray mixture.

Poast

(0.75–2.5 pt)

or

Poast Plus

(1.0–3.75 pt)

sethoxydim

Apply for control of most annual and perennial grasses, before grasses exceed 4" tall. Include a crop oil concentrate at 2 pt/A. Herbicide applications must be made no later than 40 days before harvest.

Select, Arrow, Shadow, others

(6–16 oz)

clethodim

Apply for the control of annual and perennial grasses. For annual grasses up to 6" tall apply 6 oz/A. A second application may be made. Higher rates will be necessary for rhizome johnsongrass, bermudagrass, and other perennial grasses. Add crop oil concentrate at 1 gal per 100 gals. of spray mixture.

Select Max or TapOut

(12–32 oz)

clethodim

Control will be similar to Select, Arrow, or Trigger. Select Max can be applied with either a crop oil or nonionic surfactant.

Staple LX

(2.6–3.8 oz)

pyrithiobac

Apply overtop of cotton from cotyledonary stage up to 60 days of harvest. Avoid applying shortly before or after cool weather. Include nonionic surfactant at 0.25% by volume (1 qt per 100 gal spray mix). Do not add crop oil. May make two applications per year, not exceeding a total of 5.1 fl oz. May mix with 1 pt/A of MSMA when cotton is 3 to 6 inches to improve sicklepod control; however, this mixture may reduce pigweed control by Staple.

Suggest not mixing with grass control herbicides. May tank mix with most insecticides, but do not tank mix with

any product containing malathion. Do not mix with any Dual product. Separate Staple and Dual applications by 5 or more days. See label for rotational restrictions.

DIRECTED POSTEMERGENCE

Aim 2EC

0.8–1.6 oz

carfentrazone

Apply as a directed spray after cotton has reached 12" in height with sufficient bark development. Direct spray below foliage or leaf burning will occur. For best activity weed height should be less than 4" in height. See herbicide label for specific rate information. Applications should be made with crop oil concentrate at 1% v/v.

Cotoran 4L or Meturon 4L

(2.4 pt)

or

Cotoran DF or Meturon DF

(1.5 lb)

+

MSMA

(several formulations)

fluometuron

+

MSMA

Apply as a directed spray after cotton is 3"–4" tall. Add a surfactant if not included in MSMA formulation. Controls a broad spectrum of weeds. Do not apply over the top of cotton. Do not apply after cotton begins blooming.

Caparol 4L

(1.3–2.4 pt)

+

MSMA

(2.5 pt)

prometryn

+

MSMA

Apply this tank mixture as a directed spray after cotton is 6" tall. Add a surfactant if not included in MSMA formulation. Broad spectrum weed control. Do not apply over the top of cotton. Do not apply after cotton is blooming.

Direx 4F

(0.8–2.4 pt)

+

MSMA

(2.5 pt)

diuron

+

MSMA

Apply in >12" cotton for grass, broadleaf, and sedge control. Higher diuron rates will provide increased soil residual activity. For control of large morningglory, Aim 2EC may be added. If including Aim, delay application until cotton reaches 16" in height.

ET

(0.5–1 oz)

pyraflufen-ethyl

Apply after cotton reaches 18" with 3" of basal bark. Weeds should be 6" or less at time of application. Avoid contact of spray with desirable foliage. Do not apply more than 1 oz per season. Glyphosate or MSMA may be added to improve grass or nutsedge activity. Information on the full weed spectrum controlled by this herbicide is currently limited.

Goal 2XL

(1.0–2.0 pt)

oxyfluorfen

Apply as a directed spray to weeds less than 4" tall and after cotton is 8" tall. Cotton foliage sprayed will be injured.

Cobra

(13 oz)

+

MSMA

(several formulations)

lactofen

+

MSMA

Apply as a directed spray to weeds 4" tall and after cotton is 8" tall, but preferably 12" tall, and broadleaf weeds are 3" to 5" smaller than the lowest cotton leaves. Cotton foliage sprayed will be injured. Add a crop oil if stem bark is present; use non-ionic surfactant prior to bark formation. The use of crop oil will cause more cotton injury if the spray contacts green stem tissue.

Layby Pro

(2 pt)

+

MSMA

(2.5 pt)

diuron + linuron

+

MSMA

Apply as directed spray in cotton that is at least 16" tall until first bloom.

Linex

(1–3 pt)

linuron

Apply 1 pt at 6" cotton followed by 1.5 pt at 8" cotton. Alternatively, cotton reaching 20" may receive 2 or 3 pt. Use a nonionic surfactant at 1 pt per 25 gal. Weed control will be similar to Diuron.

Prowl 3.3 EC

(1.8–2.4 pt)

or

Prowl H20

(2 pt)

pendimethalin

Do NOT spray over the top of cotton. Apply as a directed layby spray to cotton. Does NOT control emerged weeds. Apply after controlling existing weeds. Alternatively, pendimethalin may be tank-mixed with any registered layby herbicide, including glyphosate in Roundup Ready cotton. With adequate rainfall or irrigation for activation, pendimethalin will provide residual control of annual grasses and pigweed species. Avoid contact of spray with the non-woody portion of cotton stems and with cotton foliage or serious crop injury can result. Apply at least 60 days prior to harvest.

Suprend

(1.0–1.5 lb)

trifloxysulfuron-sodium

+

prometryne

For excellent control of morningglories, pigweeds, sicklepod, and sedges. Do not apply more than 2.7 lb/A/yr. Sequential applications can be made after 14 days. Do not apply within 60 days of harvest.

Valor

(1–2 oz)

flumioxazin

For excellent control of morningglory and numerous other broadleaf weeds. For improved grass control glyphosate should be added, or MSMA to improve sedge and Palmer amaranth control. Applications should be made when cotton has reached 16 inches in height and spray should be directed to the bottom 2 inches of the stem. A non-ionic surfactant should be added to the spray mixture at 0.25% v/v. DO NOT apply Valor with crop oil or any other spray additive except non-ionic surfactants. The manufacturer recommends that a separate sprayer be dedicated to Valor since clean-out is difficult and Valor is extremely injurious to plant foliage.

For resistance management, only use Reflex or Valor once per cropping season.

HOODED APPLICATIONS

ET

1–2 oz

pyraflufen-ethyl

Hooded applications are required for cotton with less than 3" of stem bark. Do not exceed 2 oz/A/yr with this use. Spray that escapes the hood will result in crop injury. ET can be mixed with glyphosate or other herbicides.

Several

glyphosate

(0.56 - 0.75 lb)

Controls annual and perennial grasses and broadleaf weeds. In non-Roundup Ready Cotton, keep hoods in contact with the ground and avoid contact with foliage or stems. Do not exceed 5 mph. Allow 7 days between application and harvest. To control large morningglory plants, Aim, Caparol, Direx, or Harvade may be mixed with certain glyphosate formulations.

Gramoxone 2 SL

(19–38 oz)

paraquat

DO NOT CONTACT COTTON STEMS OR FOLIAGE. Apply in a minimum of 10 GPA at a maximum of 25 PSI. Do not exceed 5 mph. Hoods should be kept as close to ground as possible. Cotton should be at least 8 inches tall. Add nonionic surfactant or crop oil concentrated according to the label. Caparol or diuron (Direx) may be mixed with paraquat. Tank mixes are usually more effective.

Table 2. 

Herbicide program for Liberty Link cotton

Trade Name and Broadcast Rate/Acre of Commercial Product

Common Name

Remarks

Liberty 280

(23–43 oz)

glufosinate

Apply to Liberty Link varieties only. May be applied from cotton emergence to early bloom. Provides excellent control of morningglory, cocklebur, and ragweed, but less effective on perennial weeds and grasses. Adequate spray coverage is essential for weed control. Do not apply more than 40 oz/A per application or 80 oz/A/yr. Not for use south of Tampa, FL (Route 60). Addition of ammonium sulfate (3 lb/A) often improves weed control. NOTE: ROUNDUP READY COTTON WILL NOT TOLERATE LIBERTY 280 APPLICATIONS.

Liberty 280

(23–29 oz)

+

Dual Magnum

(1–1.33 pt)

glufosinate

+

S-metolachlor

Apply to Liberty Link varieties only. Do not apply Dual Magnum preemergence or severe injury will occur. Dual Magnum will provide residual control of grasses (except Texas panicum) and certain broadleaf weeds. Dual Magnum will only control weeds that have not emerged. Dual Magnum will provide good control of tropical spiderwort. Leaf burning may occur after application.

Liberty 280

(23–29 oz)

+

Staple

(1.3–1.9 oz)

glufosinate

+

pyrithiobac

Apply to Liberty Link varieties only. Staple provides additional broadleaf control (particularly pigweeds) as well as residual soil activity.

Table 3. 

Herbicide program for Roundup Ready cotton

Trade Name and Broadcast Rate/Acre of Commercial Product

Common Name and Broadcast Rate/Acre of Active Ingredient

Remarks

Glyphosate (several)

glyphosate

(0.5–1.0 lb)

Apply to Roundup Ready varieties only. Avoid drift to non-Roundup Ready cotton and other sensitive crops. Apply in 5–20 gallons of spray per acre over the top from crop emergence through four-leaf stage. Directed application is required if cotton has more than four leaves. May be applied overtop twice up to the fourth true-leaf stage, unless Roundup Ready Flex cotton is used. Separate sequential applications by at least 10 days and two nodes of new growth. Different glyphosate brands contain differing amounts of active ingredient surfactant requirements. Read specific product labels prior to product use.

Glyphosate

(several)

+

Dual Magnum (and others)

(1.33 pt)

or

Sequence

(2.5 pt)

glyphosate

(0.75 lb)

+

S-metolachlor

(1.25)

Apply to Roundup Ready varieties only. Do not apply Dual Magnum preemergence or severe injury will occur. Dual Magnum will provide residual control of grasses (except Texas panicum) and certain broadleaf weeds. Dual Magnum will only control weeds that have not emerged. Dual Magnum will provide good control of tropical spiderwort. Leaf burning may occur after application.

Glyphosate

(several)

+

Staple LX

(1.3–3.8 oz)

glyphosate

(0.75 lb)

+

pyrithiobac

Apply to Roundup Ready varieties only. See above comments. Apply over the top from one to four true leaves. Do not apply overtop after cotton exceeds four-leaf stage unless it is Roundup Ready Flex. Staple LX provides additional broadleaf control as well as residual soil activity.

Avoid applying during periods of cool wet weather. Occasional injury has been associated with this mixture. Injury is worse when applications are made when humidity is high or dew is present.

Glyphosate

+

Valor

(1–2 oz)

glyphosate

(0.75 lb)

+

flumioxazin

Apply as a directed spray. Cotton must be 16" tall. Do not mix with crop oil. Direct spray to the bottom 2" of the stem. Valor provides excellent control of morningglory and significant soil residual activity. Applications of 1 oz per acre are generally sufficient to control weeds.

For resistance managment, do not use Reflex or Valor more than once per season.

Glyphosate

+

Caparol

(1–2 pt)

glyphosate

(0.75 lb)

+

prometryn

Apply as a directed spray. Cotton should be at least 8" tall for 1 pt of Caparol and 12" for rates higher than 1 pt.

Glyphosate

+

Aim 2EC

(0.8–1.6 oz)

glyphosate

(0.75 lb)

+

carfentrazone

Apply as a directed spray. Cotton must be 16" tall. Aim provides excellent control of large morningglory. Aim can also cause severe cotton injury if application is not precisely made. See Aim label for precautions.

Glyphosate

(several)

+

Direx 4F

(1–1.5 pt)

glyphosate

(0.75 lb)

+

diuron

APPLY POST-DIRECTED TO ROUNDUP READY CULTIVARS ONLY. Use 1 pt of Direx on cotton 8 to 12 inches and 1.5 pt of Direx on cotton greater than 12 inches. Add surfactant according to label. Do not add other spray additives. Compared to glyphosate alone, this combination controls bigger morningglories and provides residual control of small-seeded broadleaf weeds, such as pigweed. However, the tank mix may give less grass control than glyphosate alone. Do not reduce the rate of glyphosate.

Roundup Ready Flex Cotton

Glyphosate - 5.5 lb gallon

such as (Roundup Weathermax)

(22–32 oz)

Glyphosate - 5 lb

(24–35 oz)

Glyphosate - 4 lb

(30–44 oz)

glyphosate

(0.95–1.38 lb)

Roundup Ready Flex Cotton allows over the top applications of glyphosate all season, until 7 days prior to harvest, without threat of boll loss or reduced yield. There are no restrictions on timing of sequential applications. Can apply as much as 4 quarts of Roundup Weathermax from emergence to 60% boll crack, but no more than 5.3 quarts per acre pre season. Some glyphosate brands have been shown to cause leaf burn when applied late in the season. Do not combine the instructions in this section with those for Roundup Ready Cotton.

Table 4. 

Estimated effectiveness of recommended herbicides on common weeds in Florida cotton1

Weed Name

Treflan or Prowl

Solicam

Cotoran or

Meturon

Karmex, Direx,

Diuron

Command

Time of Application

PPI

PPI

PRE

PRE

PRE

amaranth, Palmer

F

F

G

F

P

anoda, spurred

G

-

P

P

E

barnyardgrass

E

E

G

F

E

beggarweed, Florida

P

G

G

G

F–G

bermudagrass

P

P

P

P

P

burgherkin

P

G

F–G

F

P

carpetweed

G

G

G

G

G

citronmelon

P

F

F–G

F

P

cocklebur, common

P

P

G

P

F

copperleaf, hophornbeam

P

E

E

E

E

cowpea

P

P

P

-

P

crabgrass

E

E

G

G

G

crotalaria, showy

P

-

G

G

-

croton, tropic

P

G–E

G

-

E

crowfootgrass

E

G

G

G

F

dayflower, spreading

P

-

P

P

-

eclipta

P

F

F

F

F

goosegrass

E

G

G

G

G

jimsonweed

P

F

G

G–E

G

johnsongrass (rhizome)

P

P

P

P

P

johnsongrass (seedling)

G

G

F

F

G

lambsquarters, common

G

G

E

G

G

morningglory, cypressvine

P

F

G

-

F–G

morningglory, entireleaf

P

F

G

-

F–G

morningglory, ivyleaf

P

F

G

-

F–G

morningglory, pitted

P

F

G

-

F–G

morningglory, purple

P

F

G

-

F–G

morningglory, smallflower

P

F

G

-

F–G

morningglory, tall

P

F

G

-

F–G

nutsedge, purple

P

P–F

P

P

P

nutsedge, yellow

P

P–F

P

P

P

panicum, fall

E

G

P

P

G

panicum, Texas

E

F–P

P

P

F

pigweed, redroot

E

F–G

E

E

P

pigweed, smooth

E

F–G

G–E

G

P

poinsettia, wild

P

P

P

P

F

purslane, common

E

E

F

E

G

pusley, Florida

E

G–E

G

G

G

ragweed, common

P

G

G

G

G

redweed

P

G

G

G

G

sandbur, field

E

-

G

G

F–G

senna, coffee

P

P

P

P

F

sesbania, hemp

P

P

F

P

F

sicklepod

P

F

G

P

P

sida, prickly

P

E

E

F

G

signalgrass, broadleaf

E

G

G

G

E

smartweed, Pennsylvania

P

F

P

F

E

spurge, spotted

P

F

P

F

P

starbur, bristly

P

-

G

P

P

velvetleaf

P

F

P

F

E

1 Estimated effectiveness based on rates recommended in this report. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil type, and weather conditions.

Weed Control Symbols: E = 90%–100% control; G = 80%–90% control; F= 60%–80% control; P = less than 60% control; - = insufficient observations.

Time of Application Symbols: PPI = preplant incorporated; PRE = pre-emergence.

Table 5. 

Estimated effectiveness of recommended herbicides on common weeds in Florida cotton (continued)1

Weed Name

Dual Magnum (and others)

Envoke

Liberty 2

Glyphosate 3

Poast, Fusilade DX, Assure II,

Select

Staple

Time of Application

POT4

POT

POT

POT

POT

POT

amaranth, Palmer

G

P–F

F

E

P

G

anoda, spurred

-

-

F

G

P

E

barnyardgrass/jungle rice

G

P

P–F

F

G–E

P

beggarweed, Florida

P

G

G

G–F

P

G

bermudagrass

P

P

P

F–G

G

P

burgherkin

P

-

G

G

P

G

carpetweed

G–E

-

G

E

P

G

citronmelon

P

-

G

E

P

-

cocklebur, common

P

E

G–E

E

P

G

copperleaf, hophornbeam

P

-

F–G

G

P

P

cowpea

P

-

F–G

G–E

P

G

crabgrass

E

P

G

E

E

P

crotalaria, showy

P

-

F–G

G

P

P

croton, tropic

P

P–F

G

E

P

P

crowfootgrass

G–E

P

G

E

E

P

dayflower, spreading

G–E

P–F

F

F

P

G–E

eclipta

P–F

G

F–G

G

P

-

goosegrass

G–E

P

F–G

E

E

P

jimsonweed

P

P

E

G–E

P

E

johnsongrass (rhizome)

P

P

P

E

G–E

P

johnsongrass (seedling)

F

F

P–F

E

E

P

lambsquarters, common

F–G

G

E

G–E

P

P

morningglory, cypressvine

P

G

G–E

F–G

P

G

morningglory, entireleaf

P

G

G–E

F–G

P

G

morningglory, ivyleaf

P

G

G–E

F–G

P

G

morningglory, pitted

P

G

G–E

F–G

P

G

morningglory, purple

P

G

G–E

F–G

P

G

morningglory, smallflower

P

P

G–E

F–G

P

G

morningglory, tall

P

G

G–E

F–G

P

G

nutsedge, purple

P

E

P–F

G

P

P

nutsedge, yellow

F–G

E

P–F

F

P

P

panicum, fall

G

P

G–E

E

E

P

panicum, Texas

P

P

G–E

E

G–E

P

pigweed, redroot

G

G

F

E

P

E

pigweed, smooth

G

G

F

E

P

E

poinsettia, wild

P

G

G

G–E

P

F–G

purslane, common

-

-

E

E

P

F

pusley, Florida

G–E

P

F–G

P–F

P

P–F

ragweed, common

P

G

E

E

P

P

redweed

P

G

E

E

P

G

sandbur, field

G

P

E

E

E

P

senna, coffee

P

-

E

E

P

E

sesbania, hemp

P

-

P–F

P–F

P

E

sicklepod

P

E

E

E

P

P–F

sida, prickly

P

P

G

G

P

F

signalgrass, broadleaf

F

P

E

E

E

P

smartweed, Pennsylvania

P

G

G

G

P

E

spurge, spotted

P

-

G

G

P

F

starbur, bristly

P

G

G

G

P

G

velvetleaf

P

-

G

G

P

E

1 Estimated effectiveness based on rates recommended in this report. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil type, and weather conditions.

Weed Control Symbols: E = 90%–100% control; G = 80%–90% control; F = 60%–80% control; P = less than 60% control; - = insufficient observations.

Time of Application Symbols: POT = postemergence over-the-top.

2 For use on Liberty Link varieties only.

3 For use on Roundup Ready varieties only.

4 Dual Magnum is applied POT to cotton. However, Dual Magnum will not control emerged weeds. Dual Magnum must contact the soil in order to provide preemergence activity on germinating weed seeds.

Table 6. 

Estimated effectiveness of recommended herbicides on common weeds in Florida cotton (continued)1

Weed Name

Fluometuron + MSMA

Caparol +

MSMA

Cobra +

MSMA

Diuron or Linex +

MSMA

Glyphosate + Diuron

Goal

Valor

Suprend

Time of Application

PDS

PDS

PDS

PDS

PDS

PDS

PDS

PDS

amaranth, Palmer

G

E

E

G–E

E

E

E

E

anoda, spurred

P

P

F

-

-

F

G

-

barnyardgrass

F

G

F

-

G

F

F

G

beggarweed, Florida

G

G

G

E

E

G

E

G

bermudagrass

P

P

P

P

F

P

P

-

burgherkin

P

G

G

G

G–E

G

E

G

carpetweed

G

G

G

-

G–E

G

E

-

citronmelon

P

F–G

G

F–G

G

G

G–E

G

cocklebur, common

G

G

G

E

E

E

E

E

copperleaf, hophornbeam

E

E

E

G

G–E

E

E

E

cowpea

G

G

G

G

G

F–G

-

-

crabgrass

G

G

G

F–G

G

F

F

P

crotalaria, showy

G

G

G

G

G

F

G

G

croton, tropic

G

G

G

G

E

E

E

-

crowfootgrass

G

G

F

F–G

G

P

F

-

dayflower, spreading

F

F

E

-

-

-

F–G

-

eclipta

F

F

F

-

G

G

G–E

G

goosegrass

G

G

G

F–G

G

F

F

-

jimsonweed

E

G–E

G–E

G

E

E

E

G

johnsongrass (rhizome)

P

P

F–G

P

G

P

P

P

johnsongrass (seedling)

G

G

G

F

G

F

F

P

lambsquarters, common

G

G

F

G

G–E

G

E

G

morningglory, cypressvine

G–E

G–E

G–E

G–E

G–E

G

E

G–E

morningglory, entireleaf

G–E

G–E

G–E

G–E

G–E

G

E

G–E

morningglory, ivyleaf

G–E

G–E

G–E

-

G–E

G

E

G–E

morningglory, pitted

G–E

G–E

G–E

G–E

G–E

G

E

G–E

morningglory, purple

G–E

G–E

G–E

G–E

G–E

G

E

G–E

morningglory, smallflower

G–E

G–E

G–E

G–E

G–E

G

E

G–E

morningglory, tall

G–E

G–E

G–E

G–E

G–E

G

E

G–E

nutsedge, purple

P

P–F

P

F

G

P

P–F

G–E

nutsedge, yellow

P–F

P–F

P–F

F

F

P

P–F

E

panicum, fall

G

G

G

F–G

-

F

F

E

panicum, Texas

G

G

G

F

G

F

F

-

pigweed, redroot

G

E

E

E

E

E

E

E

pigweed, smooth

G

E

E

E

E

E

E

E

poinsettia, wild

F

P

G

P

F–G

F–G

G

G

purslane, common

F

G

G

-

E

E

E

-

pusley, Florida

G

G

G

F

F

F

-

-

ragweed, common

G

G

G

G

G

G

G–E

-

redweed

G

G

G

G

F

F

-

-

sandbur, field

G

G

G

G

F–G

F

F

G

senna, coffee

P

F

P

G

G

G

G–E

F

sesbania, hemp

P

F

F

P–F

G

F

G

F

sicklepod

G

G

F–G

G–E

G–E

F

E

G–E

sida, prickly

F

G

G

G

G–E

G

E

G

signalgrass, broadleaf

G

G

G

-

G

G

F

G

smartweed, Pennsylvania

P

P

F

-

E

E

E

-

spurge, spotted

P

P

E

G

E

E

E

-

starbur, bristly

G

G

G

G

G

F

G–E

G

velvetleaf

F

F

G

G

G–E

G

E

-

1 Estimated effectiveness based on rates recommended in this report. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil type, and weather conditions.

Weed Control Symbols: E = 90%–100% control; G = 80%–90% control; F = 60%–80% control; P = less than 60% control; - = insufficient observations.

Time of Application Symbols: PDS = post-directed spray.

Footnotes

1.

This document is SS-AGR-04, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date January 2000. Revised March 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

J. A. Ferrell, associate professor, Agronomy Department; G. E. MacDonald, professor, Agronomy Department; and R. Leon, assistant professor, Agronomy Department, UF/IFAS West Florida Research and Education Center, Milton, FL; UF/IFAS Extension, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.