UC IPM: Information about Herbicides in Cotton

UC Pest Management Guidelines

Flowers of morningglory, Ipomoea sp. range from violet to red.

Herbicide

Amount/Acre

R.E.I.+

P.H.I.+

(commercial name)

(hours)

(days)

WINTER FALLOW BEDS

Before weeds emerge

PROMETRYN

1.6–2 lb a.i.

(Caparol) 4L

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.

OXYFLUORFEN

0.25–0.5 lb a.i.

(Goal) 2XL

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 postemergent 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 preemergent activity. Incorporate at least 2 inches deep before planting. Do not rotate to any crop other than cotton for 10 months following application.

After weeds emerge

GLYPHOSATE

Label rates

see label

(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.

PARAQUAT*

0.5–1 lb a.i.

(Gramoxone Inteon)

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.

FLUMIOXAZIN

0.064–0.096 lb a.i.

(Chateau)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

COMMENTS: Provides both pre- and postemergent 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/irrigation to activate preemergent control. See label for plant back restrictions. Avoid drift to prevent injury to nontarget crops. Often combined with glyphosate for both grass and broadleaf control.

CARFENTRAZONE

0.016–0.024 lb a.i.

(Shark)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

COMMENTS: Provides postemergent broadleaf control. Often combined with glyphosate for both grass and broadleaf control. Avoid drift to prevent injury to nontarget 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.

OXYFLUORFEN

0.25–0.5 lb a.i.

(Goal)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

. . . PLUS . . .

PARAQUAT*

0.5–1 lb a.i.

(Gramoxone Inteon)

WSSA MODE OF ACTION GROUP NUMBER¹: 22

. . . or . . .

GLYPHOSATE

0.25–0.5 lb a.i.

(Roundup)

WSSA MODE OF ACTION GROUP NUMBER¹: 9

COMMENTS: Apply with a nonionic surfactant to large weeds (greater than 6 inches) and volunteer cereals.

PROMETRYN

1.2–2.4 lb a.i.

(Caparol) 4L

WSSA MODE OF ACTION GROUP NUMBER¹: 5

. . . PLUS . . .

TRIFLURALIN

0.5–1 lb a.i.

(Treflan)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

. . . or . . .

PENDIMETHALIN

0.5–1.425 lb a.i.

(Prowl)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Apply just before planting for control of solanaceous weeds (hairy and black nightshade).

FLUMIOXAZIN

0.0637–0.0956 lb a.i.

(Chateau)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

. . . PLUS . . .

TRIFLURALIN

0.5–1 lb a.i.

(Treflan)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

. . . or . . .

PENDIMETHALIN

0.5–1.425 lb a.i.

(Prowl)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Apply just before planting for control of solanaceous weeds (hairy and black nightshade).

PREPLANT

PENDIMETHALIN

0.5–1.425 lb a.i.

(Prowl)

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).

TRIFLURALIN

0.5–1.25 lb a.i.

(Treflan)

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 2–4 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 14 months after a spring application or 16 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).

PROMETRYN

1.2–2.4 lb a.i.

(Caparol) 4L

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/season. Cabbage, okra, onions, peas, red beets, and sweet corn can be planted in fall following one preplant or one layby application/season. Spring-seeded crops should not be planted until after April 1.

METAM SODIUM*

213–319.5 lb a.i.

(Vapam)

50–75 gal

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 phosphorous fertilizer has helped correct this problem. Either tank mix the phosphorous with metam or apply it at planting.

PROMETRYN

1.2–2.4 lb a.i.

(Caparol) 4L

WSSA MODE OF ACTION GROUP NUMBER¹: 5

. . . PLUS . . .

TRIFLURALIN

0.5–1 lb a.i.

(Treflan)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

. . . or . . .

PENDIMETHALIN

0.5–1.425 lb a.i.

(Prowl)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

COMMENTS: Apply just before planting for control of solanaceous weeds (hairy and black nightshade).

POSTPLANT – Over-the-Top (OT) or Post-directed spray (PDS)

CLETHODIM

0.06–0.12 lb a.i.

(Select Max)

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.

DIURON

0.4 lb a.i.

(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. Do not use in Kern County. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.

FLUAZIFOP-P-BUTYL

0.125–0.375 lb a.i. (OT)

(Fusilade DX)

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. Retreatment may be necessary. Do not apply after boll set or within 90 days of harvest. Do not apply more than 48 oz/acre/season.

GLYPHOSATE Label rates for Roundup Ready varieties

(Roundup)

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 applications. Over-the-top 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.

METOLACHLOR

0.95–1.26 lb a.i.

(Dual Magnum)

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 plant back restrictions.

MSMA

1–1.875 lb a.i. (OT)

1–1.995 lb a.i. (PDS)

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/season OT or twice PDS. Generally for nutsedge. Do not apply after first bloom.

OXYFLUORFEN

0.25–0.50 lb a.i. (PDS)

(Goal)

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.

PROMETRYN

0.5–0.65 lb a.i.

(Caparol) 4L

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.

PYRITHIOBAC SODIUM

1–1.4 oz a.i. (OT)

(Staple)

MODE OF ACTION: Unknown

COMMENTS: Make a band application 8–10 inches wide over the top of the cotton. Applications, which may also be applied as a post-directed spray, 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, and/or crinkling of cotton leaves when applied over the top, 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 field bioassay. Double disc or plow fields before planting.

SETHOXYDIM

0.28–0.39 lb a.i. (OT)

(Poast)

WSSA MODE OF ACTION GROUP NUMBER¹: 1

COMMENTS: Apply to control both annual and perennial grasses. Use 2 pt crop oil concentrate/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. Retreatment 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

MSMA

1.0–1.995 lb a.i. (PDS)

WSSA MODE OF ACTION GROUP NUMBER¹: 17

. . . PLUS . . .

PROMETRYN

0.5–0.65 lb a.i.

(Caparol) 4L

WSSA MODE OF ACTION GROUP NUMBER¹: 5

COMMENTS: Apply post-directed to small seedlings when cotton is at least 8 inches tall.

PYRITHIOBAC SODIUM

1–1.4 oz a.i. (OT)

(Staple)

MODE OF ACTION: Unknown

. . . PLUS . . .

MSMA

1.875 lb a.i. (OT)

WSSA MODE OF ACTION GROUP NUMBER¹: 17

COMMENTS: Use for morningglory control.

PYRITHIOBAC SODIUM

1–1.4 oz a.i. (OT)

(Staple)

MODE OF ACTION: Unknown

. . . PLUS . . .

SETHOXYDIM

(Poast)

0.29–0.46875 lb a.i. (OT)

WSSA MODE OF ACTION GROUP NUMBER¹: 1

. . . or . . .

CLETHODIM

(Select Max)

0.08–0.17 lb a.i. (OT)

WSSA MODE OF ACTION GROUP NUMBER¹: 1

. . . or . . .

FLUAZIFOP-P-BUTYL

(Fusilade DX)

0.24–0.375 lb a.i. (OT)

WSSA MODE OF ACTION GROUP NUMBER¹: 1

COMMENTS: Tank mix applications of pyrthiobac sodium with postemergent grass herbicides can result in antagonism and partial or delayed grass control. To avoid poor grass control, use tank mixes of clethodim or fluazifop-p-butyl with pyrithiobac sodium for perennial grass control. For annual grass control, use a tank mix of sethoxydim or clethodim with pyrithiobac sodium. Because tank mixes with clethodim and pyrthiobac sodium have shown no anatgonism, this tank mix is the best choice if both annual and perennial grasses need to be controlled.

LAYBY

Before weeds emerge

METOLACHLOR

0.95–1.26 lb a.i.

(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 plant back restrictions.

DIURON

0.8–1.6 lb a.i.

(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-7) 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. Do not use diuron in Kern County. Considered to be a ground water contaminant and requires a use permit within Ground Water Protection Areas.

OXYFLUORFEN

0.5 lb a.i.

(Goal)

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/season. Do not plant any crop other than cotton and onions within 10 months of application.

TRIFLURALIN

0.5–0.75 lb a.i.

(Treflan)

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 14 months after spring or 16 months after fall application.

After weeds emerge

CARFENTRAZONE

0.016–0.024 lb a.i.

(Shark)

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 plant back restrictions.

PYRAFLUFEN ETHYL

0.7371 grams a.i. (0.026 oz a.i.)

(ET)

MODE OF ACTION: Unknown

COMMENTS: Provides good postemergent 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 plant back restrictions.

TRIFLOXYSULFURON

Label rates

(Envoke)

WSSA MODE OF ACTION GROUP NUMBER¹: 2

COMMENTS: Provides good postemergent control of many broadleaf weeds and nutsedge. Apply to actively growing weeds less than 4 inches high or 3-inch rosettes. Apply postemergence to cotton that is 5 inches or taller, or at layby. To minimize cotton injury, direct spray at the base of the cotton plant at layby. Check label for plant back restrictions.

GLUFOSINATE

0.786 lb a.i.

(Ignite)

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-top 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 post-directed. There are no rotational restrictions.

OXYFLUORFEN

0.5 lb a.i.

(Goal)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

PROMETRYN

1.2–1.6 lb a.i.

(Caparol) 4L

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/year. Spring-seeded crops in California should not be planted until after April 1. Do not use in Coachella Valley.

METOLACHLOR

0.95–1.26 lb a.i.

(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 plant back restrictions.

DIURON

0.8–1.6 lb a.i.

WSSA MODE OF ACTION GROUP NUMBER¹: 7

TRIFLURALIN

0.5–0.75 lb a.i.

(Treflan)

WSSA MODE OF ACTION GROUP NUMBER¹: 3

PREHARVEST

CARFENTRAZONE

0.016–0.024 lb a.i.

(Shark)

WSSA MODE OF ACTION GROUP NUMBER¹: 14

GLYPHOSATE

1–1.89 lb a.i.

see label

(Roundup)

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.

GLYPHOSATE

1 lb a.i.

see label

(Roundup)

WSSA MODE OF ACTION GROUP NUMBER¹: 9

. . . PLUS . . .

TRIBUPHOS*

0.75–1.87 lb a.i.

see label

(Def6, Folex)

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.

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/.

Not applicable.

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

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r114700311.html revised: August 7, 2009. Contact webmaster.

How to Manage Pests

UC Pest Management Guidelines

Cotton

Herbicide Treatment Table

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