Cotton

Pest Management Guidelines


Herbicide Treatment Table

(Reviewed 5/13, updated 5/13)

In this Guideline: More about weeds in cotton:

Herbicide Amount per acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in alphabetical order. When choosing a pesticide, consider information relating to environmental impact, resistance management, the pesticide's properties, and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
WINTER FALLOW BEDS
 
Before weeds emerge
 
A. OXYFLUORFEN 0.25–0.5 lb a.i. 24 NA
  (Goal) 2XL 1–2 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: Apply before weeds germinate or seedlings are more than 6 inches tall, depending on species. (Provides both pre- and postemergence control.) Aerial applications can be made between Oct 1 and 31 in Fresno, Kern, Kings, Madera, Merced, and Tulare counties. Preirrigation or rainfall should occur within 3–4 weeks for best preemergence activity. Incorporate at least 2 inches deep before planting. Do not rotate to any crop other than cotton for 10 months following application.
 
B. PROMETRYN 1.6–2 lb a.i. 12 NA
  (Caparol) 4L 3.2–4 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Apply before weeds germinate or weed seedlings are more than 2 inches tall, depending on species. Rainfall or sprinkler irrigation is required for soil activity. Do not use on sand or loamy sand soils. To avoid illegal residues do not apply more than 10.3 pt on sandy loam or 11.9 pt on medium to fine soils/year. See label for plantback restrictions.
 
After weeds emerge
 
A. CARFENTRAZONE 0.016–0.024 lb a.i. 12 NA
  (Shark) 1.0–1.5 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: Provides postemergence broadleaf control. Often combined with glyphosate for both grass and broadleaf control. Avoid drift to prevent injury to nontarget crops.
 
B. FLUMIOXAZIN Up to 2.04 oz a.i. 12 NA
  (Chateau) 4 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: Provides both pre- and postemergence control. The 2 oz rate can be applied 30 days before planting and the 3 oz rate at 60 days before planting. Needs at least 1/4 inch of rainfall or irrigation to activate preemergence control. See label for plantback restrictions. Avoid drift to prevent injury to nontarget crops. Often combined with glyphosate for both grass and broadleaf control.
 
C. GLYPHOSATE Label rates See label NA
  (Roundup)      
  WSSA MODE OF ACTION GROUP NUMBER1: 9
  COMMENTS: Apply after maximum weed emergence, but before weeds are greater than 6 inches tall. Allow at least 3 days after treatment before tillage. Avoid drift to prevent injury to nontarget crops.
 
D. PARAQUAT* 0.5–1 lb a.i. 12 NA
  (Gramoxone Inteon) 2–4 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 22
  COMMENTS: Apply with a nonionic surfactant to weeds 1–6 inches tall. Avoid drift to prevent injury to non-target crops.
 
Herbicide combinations: for tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
PREPLANT
 
A. METAM SODIUM* 213–319.5 lb a.i.    
  (Vapam) 50–75 gal See label NA
  COMMENTS: A soil fumigant used for preplant control of annual broadleaves (including nightshade) and grasses; provides partial control of perennials. Nutsedge control is erratic on sandy soils and poor on clay loam soils. Prepare a firm, trash- and clod-free seedbed and preirrigate the soil to ensure that weed seeds have imbibed water. Soil temperatures should be between 50° and 90°F. Use a shallow 6- to 8-inch spray blade to apply a band on top of the cotton bed. Nutsedge control is improved with a 2-3 tiered spray blade or using staggered fertilizer knives. Cover or cap with a 2- to 3-inch layer of soil; place the material deep enough so that treated soil will not be disturbed by the planting operation. Planting may take place 14-21 days after treatment, depending on amount applied as indicated on label. Be sure not to contaminate treated soil with untreated soil during planting or subsequent cultivations. Best results are obtained if soil is undisturbed between application and planting. Apply preplant fertilizer before the metam sodium. Yield reduction can occur because of the reduction of mycorrhizal fungi in the soil; the addition of phosphorus fertilizer has helped correct this problem. Either tank mix the phosphorus with metam or apply it at planting.
 
B. PENDIMETHALIN 0.5–1.425 lb a.i. 24 NA
  (Prowl 3.3 EC) 1.2–3.5 pt    
  (Prowl H2O) 1–3 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Can be applied after Oct 15, up to 140 days before planting or immediately before planting. Apply higher rates when application is 140 days before planting. Incorporate within 7 days of application into the top 2–4 inches of soil. May be combined with liquid fertilizers. Tank mixing with prometryn provides fair-to-good control of nightshades, depending on soil moisture (See combinations below).
 
C. PROMETRYN 1.2–2.4 lb a.i. 12 NA
  (Caparol 4L) 2.0–4.8 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Preirrigate before application. Apply immediately before planting cotton. Incorporate to 4 inches immediately after application. Do not use on sand, loamy sand, calcareous soil, or soil high in salts. Do not use more than 10.3 pt prometryn on sandy loam soil or 11.9 pt on medium- to fine-textured soils per season. Cabbage, okra, peas, and sweet corn can be planted in fall following one preplant or one layby application per season. Onions and red beets may not be planted within 8 months of applying Caparol 4L. Spring-seeded crops should not be planted until after April 1.
 
D. TRIFLURALIN 0.5–1.25 lb a.i. 12 90
  (various Treflan formulations) 1.0–2.5 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Can be applied after Oct 15 or immediately before planting. If applied in fall, use higher rates. Incorporate into 2–3 inches of soil within 24 hours after application. Sugarbeet, red beets, or spinach should not be planted for 12 months after spring application, or 14 months after fall application. Sorghum, corn, or oats should not be planted for 12 months after a spring application or 14 months after a fall application. If land is not preirrigated, plantback restrictions increase. Tank mixing with prometryn provides fair-to-good control of nightshades, depending on soil moisture (See combinations below).
 
Herbicide combinations: for tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
POSTPLANT: OVER-THE-TOP (OT)2 OR POSTDIRECTED SPRAY (PDS)3
 
A. CLETHODIM 0.06–0.12 lb a.i. 24 60
  (Select Max) 8–16 fl oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: Apply to actively growing grasses. Tank mix with a crop oil concentrate. Can be applied by air or ground.
 
B. DIURON 0.4 lb a.i. 12 NA
  (Karmex, Direx)      
  WSSA MODE OF ACTION GROUP NUMBER1: 7
  COMMENTS: Apply when cotton is at least 6 inches tall and weeds do not exceed 2 inches. Contact with cotton foliage will result in injury. Cotton, corn, or grain sorghum may be planted the next spring, but do not replant treated areas to any other crop within 1 year following the last application. Use in Kern County is not advisable. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.
 
C. FLUAZIFOP-P-BUTYL (OT) 0.125–0.375 lb a.i. 12 90
  (Fusilade DX) 8–16 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: Apply to control both annual and perennial grasses. Use a crop oil concentrate or nonionic surfactant. Apply to annual grasses when 1–4 inches and actively growing without water stress; apply to perennials such as bermudagrass when stolons are 4–8 inches long and johnsongrass is 8–18 inches high. Re-treatment may be necessary. Do not apply after boll set or within 90 days of harvest. Do not apply more than 48 oz/acre/season.
 
D. GLYPHOSATE (Label rates for Roundup Ready varieties)
  (Roundup) See label See label See label
  WSSA MODE OF ACTION GROUP NUMBER1: 9
  COMMENTS: For traditional cotton varieties, spot-treat perennial weeds just at or before seedhead or flower formation. Repeat treatments may be necessary, but do not exceed 5.3 qt/acre/year. Do not till for at least 7–10 days after application or harvest within 7 days of application. Will kill or severely injure cotton. With Roundup Ready Flex systems there are no restrictions on timing of sequential applications. There is also the potential to combine insecticide or mepiquat into over-the-top applications2. Over-the-top2 applications can be made in Roundup-Ready cotton up until the fourth leaf stage. Applications after cotton has more than four leaves must be directed or applied with a hooded sprayer.
 
E. METOLACHLOR 0.95–1.26 lb a.i. 24 80-100
  (Dual Magnum) 1.0–1.33 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 15
  COMMENT: Incorporate with rolling cultivator and irrigate. Apply before weeds emerge 14 days before planting. Rates will vary with soil type. Check label for plantback restrictions. PHI: 80 days for directed sprays, 100 days for over-the-top2 applications.
 
F. MSMA (OT) 1–1.875 lb a.i. 12 NA
  6.6/6 Plus (OT) 1.2–2.3/1.3–2.5 pt    
 
  MSMA (PDS) 1–1.995 lb a.i. 12 NA
  6.6/6 Plus (PDS) 1.2–2.4/1.3–2.66 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 17
  COMMENTS: Apply to cotton after 3 inches tall; injury is less when cotton is small. Later applications are better applied as a directed spray. Weeds should be no more than 2 inches tall. Reddish discoloration will disappear with next irrigation. Do not apply more than once per season OT or twice PDS, however, the label allows up to two applications per season for both. Generally for nutsedge. Do not apply after first bloom.
 
G. OXYFLUORFEN (PDS) 0.25–0.50 lb a.i. 24 75
  (Goal) (PDS) 1–2 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: Apply to cotton that is at least 8 inches tall. Weed seedlings should have no more than 4 true leaves and be actively growing. Contact with cotton foliage will result in injury. Apply with a nonionic surfactant. Do not apply more than 2 pt in a single application or more than 4 pt/season.
 
H. PROMETRYN 0.5–0.65 lb a.i. 12 NA
  (Caparol) 4L 1.0–1.3 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Apply to cotton that is 6 or more inches high. Weeds should be less than 2 inches tall. Apply with a nonionic surfactant. Contact with cotton foliage will result in injury. Do not apply more than 10.3 pt on sandy loam soils or 11.9 pt on medium- or fine-textured soils. Don't plant spring-seeded crops until after April 1.
 
I. PYRITHIOBAC SODIUM (OT) 1–1.4 oz a.i. 24 60
  (Staple) (OT) 1.2–1.6 oz    
  MODE OF ACTION: Unknown
  COMMENTS: Make a band application 8–10 inches wide over-the-top2 of the cotton. Applications, which may also be applied as a postdirected spray3, can be made anytime after the cotton has reached the first visible true leaf; weeds should be in the seedling stage and actively growing. Pyrithiobac sodium causes temporary yellowing, bronzing, or crinkling of cotton leaves when applied over the top2, especially under cool conditions. Symptoms are more evident and remain longer in Pima cotton than in Acala cottons. Plantback intervals for pyrithiobac sodium include: tomatoes 8 months; wheat 6 months; and cotton anytime. All other crops require a minimum of 10 months and a field bioassay. Double disc or plow fields before planting.
 
J. SETHOXYDIM (OT) 0.28–0.39 lb a.i. 12 40
  (Poast) (OT) 1.5–2.0 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 1
  COMMENTS: Apply to control both annual and perennial grasses. Use 2 pt crop oil concentrate per acre. Apply to actively growing annual grasses that are not water stressed and between 4–8 inches high. Perennials such as bermudagrass should have stolons 6 inches or less; johnsongrass 6–10 inches tall. Re-treatment may be necessary. Do not cultivate within 5 days of application or harvest within 40 days following application. Cotton at all stages of growth is tolerant to sethoxydim.
 
Herbicide combinations: for tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
LAYBY
 
Before weeds emerge
 
A. DIURON 0.8–1.6 lb a.i. 12 NA
  (Karmex)      
  WSSA MODE OF ACTION GROUP NUMBER1: 7
  COMMENTS: Apply as a band treatment when cotton is at least 12 inches tall (20 inches for Pima S-2) to soil beneath cotton plants and between rows immediately after last cultivation. Irrigate within 3–4 days after application. Do not apply to sandy soils or soils with organic matter less than 1%. To avoid crop injury do not exceed 1 lb/acre on sandy loam, 1.8 lb/acre on clay loam or 2.75 lb/acre on clay during the crop season. Cotton, corn, or grain sorghum may be planted the following spring, but do not replant treated area to any other crops within 1 year of application. Use in Kern County is not advisable. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.
 
B. METOLACHLOR 0.95–1.26 lb a.i. 24 80–100
  (Dual Magnum)      
  WSSA MODE OF ACTION GROUP NUMBER1: 15
  COMMENT: Incorporate with rolling cultivator and irrigate. Apply before weeds emerge. Rates will vary with soil type. Check label for plantback restrictions. PHI: 80 days for directed sprays, 100 days for over-the-top2 applications.
 
C. OXYFLUORFEN 0.5 lb a.i. 24 75
  (Goal) 2 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: at application weed seedlings should have no more than 4 true leaves. Cotton must be at least 8 inches tall. Irrigate before spraying and within 2 weeks following application to maximize control of nightshade and ground cherries. Crop injury will occur if cotton foliage is sprayed. Do not apply more than 2 pt in a single application or 4 pt per season. Do not plant any crop other than cotton and onions within 10 months of application.
 
D. TRIFLURALIN 0.5–0.75 lb a.i. 12 90
  (various Treflan formulations) 1.0–1.5 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Direct applications between the rows and beneath cotton plants after last cultivation. Incorporate in top 2–3 inches of soil immediately. Do not apply within 90 days of harvest. Sugarbeets, red beets, or spinach should not be planted for 12 months after spring application or 14 months after fall application. Sorghum, corn, or oats should not be planted for 12 months after spring or 14 months after fall application. If land is not preirrigated, plantback restrictions increase.
 
After weeds emerge
 
A. CARFENTRAZONE 0.016–0.024 lb a.i. 12 7
  (Shark) 1.0–1.5 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: Apply to actively growing weeds less than 4 inches high or 3-inch rosettes. Apply layby to 12-inch tall or taller cotton with callused bark on the lower stem. Use directed, hooded, or shielded spray equipment. To minimize cotton injury, direct spray at the base of the cotton plant. Check label for plantback restrictions.
 
B. DIURON 0.8–1.6 lb a.i. 12 NA
  WSSA MODE OF ACTION GROUP NUMBER1: 7
  COMMENTS: Apply as a band treatment when cotton is at least 12 inches tall (20 inches for Pima S-2) to soil beneath cotton plants and between rows immediately after last cultivation. Irrigate within 3–4 days after application. Do not apply to sandy soils or soils with organic matter less than 1%. To avoid crop injury do not exceed 1 lb/acre on sandy loam, 1.8 lb/acre on clay loam or 2.75 lb/acre on clay during the crop season. Cotton, corn, or grain sorghum may be planted the following spring, but do not replant treated area to any other crops within 1 year of application. Use of diuron in Kern County is not advisable. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.
 
C. GLUFOSINATE 0.786 lb a.i. 12 70
  (Rely) 43 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 10
  With the Liberty Link cotton, spray according to weed size, not cotton growth stage; however, weeds should be sprayed when less than 5 true leaves for best control. There are no stage-of-growth restrictions for over-the-top2 applications. Provides broad-spectrum weed control and grass suppression at label rates with a maximum of 72 oz per season. Can be applied to non-Liberty Link cotton with hooded sprayers or postdirected3. There are no rotational restrictions.
 
D. METOLACHLOR 0.95–1.26 lb a.i. 24 80–100
  (Dual Magnum)      
  WSSA MODE OF ACTION GROUP NUMBER1: 15
  COMMENT: Incorporate with rolling cultivator and irrigate. Apply before weeds emerge. Rates will vary with soil type. Check label for plantback restrictions. PHI: 80 days for directed sprays, 100 days for over-the-top2 applications.
 
E. OXYFLUORFEN 0.5 lb a.i. 24 75
  (Goal) 2pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
  COMMENTS: at application weed seedlings should have no more than 4 true leaves. Cotton must be at least 8 inches tall. Do not apply within 75 days of harvest. Irrigate before spraying and within 2 weeks following application to maximize control of nightshade and ground cherries. Crop injury will occur if cotton foliage is sprayed. Do not apply more than 2 pt in a single application or 4 pt per season. Do not plant any crop other than cotton and onions within 10 months of application.
 
F. PROMETRYN 1.2–1.6 lb a.i. 12 NA
  (Caparol) 4L 2.4–3.2 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Apply before weeds are 2 inches tall; include a nonionic surfactant. Cotton must be at least 12 inches tall (18 inches when flood nozzles used). Contact of spray on cotton foliage will result in injury. Do not use on sand, loamy sand, calcareous soils, or soil high in salts. Do not use more than 10.3 pt on sandy loam soils or 11.9 pt on medium or fine soil per year. Spring-seeded crops in California should not be planted until after April 1. Do not use in Coachella Valley.
 
G. PYRAFLUFEN ETHYL 0.5–2.0 fl oz 12 7
  (ET)      
  MODE OF ACTION: Unknown
  COMMENTS: Provides good postemergence control of many broadleaf weeds. Apply to actively growing weeds less than 4 inches high or 3-inch rosettes. Apply layby to 12-inch tall or taller cotton with callused bark on the lower stem. Use directed, hooded, or shielded spray equipment. To minimize cotton injury, direct spray at the base of the cotton plant. Check label for plantback restrictions.
 
H. TRIFLURALIN 0.5–0.75 lb a.i. 12 90
  (various Treflan formulations) 1.0–1.5 pt    
  WSSA MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Direct applications between the rows and beneath cotton plants after last cultivation. Incorporate in top 2–3 inches of soil immediately. Do not apply within 90 days of harvest. Sugarbeets, red beets, or spinach should not be planted for 12 months after spring application or 14 months after fall application. Sorghum, corn, or oats should not be planted for 12 months after spring or 14 months after fall application. If land is not preirrigated, plantback restrictions increase.
 
PREHARVEST
 
A. CARFENTRAZONE 0.016–0.024 lb a.i. 12 7
  (Shark) 1.0–1.5 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 14
 
B. GLYPHOSATE 1–1.89 lb a.i. See label See label
  (Roundup) 22–44 oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 9
  COMMENTS: Apply after 60% of the cotton bolls have opened or at 8 nodes above cracked boll (NACB). Do not harvest for at least 7 days after application. Do not exceed 5.3 qt/acre in any one year or apply during this period to cotton grown for seed. Avoid drift to nontarget crops.
 
C. GLYPHOSATE 1 lb a.i. See label See label
  (Roundup) 22oz    
  WSSA MODE OF ACTION GROUP NUMBER1: 9
  . . . PLUS . . .
  TRIBUPHOS* 0.75–1.87 lb a.i. See label See label
  (Folex 6) 1.0–2.5 pt    
  MODE OF ACTION: Unknown
  COMMENTS: Apply after 60% of the cotton bolls are open for control of perennial grasses and field bindweed at time of defoliation. Use higher rates of DEF for rank and long staple cotton.
 
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. in some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
1 Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode of action numbers are useful in planning mixtures or rotations of herbicides with different modes of action. For more information, see http://www.plantprotection.org/HRAC/.
2 Over-the-top: in cotton that is tolerant of certain herbicides (e.g., Round-up Ready), herbicides can be applied after cotton has emerged. Applications can be made from the time cotyledons emerge to the appearance of the first true leaves.
3 Postdirected: A height differential between cotton plants (taller) and weeds (smaller) is necessary. Using a shielded or hooded sprayer, the herbicide is applied to cotton stems, targeting weeds at their base.
NA Not applicable.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

Weeds
  • S. D. Wright, UC Cooperative Extension, Tulare County
  • D. J. Munier, UC Cooperative Extension, Glenn County
Acknowledgment for contributions to Weeds:
  • R. N. Vargas, UC Cooperative Extension, Madera County
  • T. S. Prather, Plant, Soil, and Entomological Sciences, Univ. of Idaho, Moscow, Idaho

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