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Publication #HS201

Weed Control in Carrot1

Peter J. Dittmar and William M. Stall2

Although carrots may be grown on mineral soils, production in Florida is almost exclusively on the organic soils of central and south Florida. While the practice of seeding the crop in six lines per bed enhances total yield that may be harvested per acre, it also mostly prevents the use of mechanical cultivation for weed control.

Control of weeds is extremely important in several aspects. Because weeds directly compete with carrots for nutrients, space, and water, they reduce the size of carrot roots and thus reduce overall yield. Weeds also cause carrot roots to be deformed and therefore unmarketable. Weeds that present late in the season may also cause severe harvesting problems.

Weed control is critical early in the season because it will allow the formation of good, straight roots, and it is important for the above reasons throughout the growing season.

Currently, only linuron is labeled for preemergence (both carrots and weeds) application on muck soils, and only linuron, pendimethalin, and trifluralin are labeled for preemergence on mineral soils.

Linuron and metribuzin may be applied over the top of carrots to control small broadleaf weeds. Great care should be taken to apply these herbicides at the correct rate and at the correct growth stage of the crop and weeds (see Table 2). Carefully read the labels for directions.

Fusilade® DX, Poast®, and Select® are labeled for the control of emerged grass weeds. These may be applied several times during the growing season, up until 45 days before harvest for Fusilade® and 30 days before harvest for Poast® and Select®.

Included in the tables is the mode of action (MOA) code. These numbered codes assist growers with rotating herbicide modes of action to reduce the risk of developing herbicide resistance.

Read and follow all label directions for each herbicide used.

Tables

Table 1. 

Chemical weed control before carrot emergence

Active Ingredient

lb. a.i./acre

Trade name

Formulation/acre

MOA

Code

Weeds Controlled / Remarks

Carfentrazone

up to 0.031

(Aim®) 2 EC or 1.9 EW

up to 2 fl. oz.

14

Emerged broadleaf weeds. Apply as a preplant burn down for emerged broadleaf weeds. Use crop oil concentrate or nonionic surfactant at recommended rates. Maximum rate of 0.096 lb. a.i./acre per season. No preplant interval.

Glyphosate

(various formulations)

consult labels

9

Emerged broadleaf and grass weeds. Apply as a preplant burn down. Consult label for individual product directions.

Linuron

0.5–1.0

(Lorox® DF) 50 DF

1-2 lb.

7

A single application after planting and before crop emergence. Plant seed at least 0.5 inch deep. Preemergence and postemergence applications should not exceed 4 lb./acre per season.

Paraquat

0.5–1.0

(Gramoxone® SL) 2 SL

2.0-4.0 pt.

(Firestorm®) 3 SL

1.3-2.7 pt.

22

Emerged broadleaf and grass weeds. Apply as a preplant burn down treatment. Apply before crop emergence. Use a nonionic surfactant.

Pelargonic Acid

(Scythe®) 4.2 EC

3 – 10%

27

Emerged broadleaf and grass weeds. Apply as a preplant burn down treatment. Scythe is a contact and nonresidual and can be tank mixed residual preemergence herbicides to lengthen control.

Pendimethalin

0.95

(Prowl® H2O) 3.8

2.0 pt.

3

Broadleaf and grass control. Apply within 2 days of planting before the emergence of the crop. PHI 60 days.

Prometryn

1–2

(Caparol®) 4 L

2–4 pt.

5

Most annual broadleaf and grass weeds. Do not exceed one application. Consult label for rotational crop restrictions.

Pyraflufen

0.0008–0.003

(ET® Herbicide/Defoliant) 0.208 EC

0.5–2.0 fl. oz.

14

Emerged broadleaf and grass weeds. Apply as a preplant burndown treatment.

Trifluralin

0.5

(Treflan®, Trifluralin) 4EC

1 pt.

(Treflan® TR-10)

5 lb.

3

Annual broadleaf and grass weeds. Do not apply to muck soils. Mineral soils with 2–5% organic material, apply 0.75 lb a.i./acre. Incorporate 4 inches or less within 8 hours of application. PHI 60 days.

Table 2. 

Postemergence chemical weed control in carrot

Active ingredient

lb. a.i. / acre

Trade name

product / acre

MOA

Code

Weeds controlled / Remarks

Carfentrazone

up to 0.31

(Aim®) 2 EC or 1.9 EW

up to 2 oz.

14

Emerged broadleaf weeds. Apply as hooded application to row middles only. Use crop oil concentrate or nonionic surfactant at recommended rates. May be tank mixed with other herbicides. Do not exceed 6.1 fl. oz. per cropping season. PHI 0 days.

Clethodim

0.09–0.13

0.07-0.13

(Select®, Arrow®) 2 EC

6–8 fl. oz.

(Select Max®) 1 EC

9-16 fl. oz

1

Perennial and annual grass weeds. In fields with heavy grass pressure or larger grass weeds, use higher rates or repeat applications 14 days apart. Use a crop oil concentrate at 1% v/v in the finished spray volume. Nonionic surfactant with Select Max. PHI 30 days.

Fluazifop

0.188

(Fusilade® DX)

12 fl. oz.

1

Actively growing grass weeds. Maximum is 48 fl. oz./acre per growing season. Withhold field flooding 45 to 60 days following application. In Palm Beach and Hendry counties a 60 day interval must be observed for flooding. PHI 45 days.

Linuron

0.5–1.0

(Lorox® DF) 50 DF

1-2 lb.

7

Apply after carrots are 3 inches tall. Repeat applications may be made but do not exceed 4 lb./acre. Can be applied following Stoddard Solvent provided that the applications are at least one day apart. Do not tank mix with Stoddard Solvent. PHI 14 days.

Metribuzin

0.25

(Metribuzin, Metri® DF, Tricor® DF) 75 DF

0.3 lb.

(MetriTM, Tricor®) 4 F

0.5 pt

5

Broad leaf. Total amount applied in a season should not exceed 0.5 lb. a.i./acre. Apply after carrots have 5-6 true leaves and weeds are les than 1 inch in height. If needed, a second application may be made after an interval of at least 3 weeks. PHI 60 days.

Pelargonic Acid

(Scythe®) 4.2 EC

3–10%

27

Emerged broadleaf and grass weeds. Direct spray to row middles. Product is a contact, nonselective, foliar applied herbicide with no residual control. May be tank mixed with several soil residual compounds.

Prometryn

1–2

(Caparol®) 4 L

2–4 pt.

5

Most annual broadleaf and grass weeds. Apply up to through 6 leaf stage of carrot. One application of 4 pt./acre or two applications of 2 pt./acre. For POST control of weeds, include NIS or COC. Consult label for rotational crop restrictions. PHI 30 days.

S-metolachlor

(Dual Magnum) 7.62 EC

15

Grass and broadleaf weeds and nutsedge. Label is a Third-Party Registration (TPR, Inc.). Use without a signed authorization and waiver of liability is a misuse of the product.

Sethoxydim

0.28–0.38

(Poast®) 1.5 EC

1.5-2.0 pt.

1

Emerged grass weeds. A maximum of 5 pt./acre applied in one season. Include a crop oil concentrate. Unsatisfactory results may occur if applied to grasses under stress. PHI 30 days.

Footnotes

1.

This document is HS201, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date March 1999. Revised June 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Peter J. Dittmar, assistant professor; and William M. Stall, professor emeritus, Horticultural Sciences Department, 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. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.


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.