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Publication #HS197

Weed Management in Sweet Corn1

Peter J. Dittmar and William M. Stall2

Mechanical cultivation of sweet corn is still widespread. Selective herbicides have been used in corn for some 40 years, decreasing the number of cultivations needed per season and substantially lowering the fossil fuel energy used in sweet corn production. Many sweet corn fields now receive one cultivation or no cultivations at all. Much of the cultivation used is to reduce surface crusting or to control weeds resistant or not controlled by the herbicide combinations selected. There is at the present time a wide selection of herbicides to control most weeds in sweet corn, but that selection is being reduced because of non-reregistration of older compounds and suspensions due to leaching into the groundwater. Alachlor (Lasso) has been restricted from use in Florida because of confirmed groundwater contamination. Atrazine also is under suspicion.

Herbicide treatments are primarily categorized on the basis of the time of application, preplanting, preemergence, and postemergence. Preplanting treatments are applied before the sweet corn is planted, either applied as a surface treatment or incorporated into the soil. Preemergence application is after the sweet corn is seeded but before sweet corn or weeds emerge. Preplant and preemergence herbicides, properly selected and applied, prevent weed competition during emergence and early seedling growth. Postemergence applications take place after the emergence of both the sweet corn and weeds and are most effective when weeds are small.

Many postemergence labels state specific ages or growth stages of the sweet corn and weeds to be sprayed. These stages may be the spike stage, five-leaf stage, or when plants are 30 in. tall. If the label specifies directing a spray to the bottom or side of a plant, care must be taken to follow these directions or severe damage may occur.

Herbicide performance depends on weather, irrigation method, and soil type, as well as proper selection for weed species to be controlled and accurate application and timing. Obtain consistent results by reading the herbicide label and other information about proper application and timing.

Recent research has shown that there is a difference in tolerance to herbicides, especially among sh2 (super sweet) cultivars. Because cultivars may have different tolerances, growers should test herbicides on a trial basis when changing cultivars.

Several sulfonyl urea herbicides labeled on field corn (i.e., Accent® and Beacon®) cause damage on a large number of sweet corn cultivars and are not recommended for use. Use only labeled herbicides and those herbicides in the proper formulations. Check the labels of each herbicide for tank mix recommendations. To avoid confusion between formulations, suggested rates listed in Tables 1 and 2 are stated in pounds of active ingredient per acre (lb. a.i. /A).

Several listed herbicides are also labeled for tank-mix combinations. Read the label of each formulation for tank-mix specifications and compatibilities. There are also several premixed herbicides labeled for sweet corn.

Read the labels for specific rates recommended.

Tables

Table 1. 

Preemergence weed control in sweet corn

Active ingredient

lb. a.i./A

(Trade name)

amount of product/A

Weeds controlled / remarks

Atrazine

Mineral

1.0–2.0

Muck

2.0–3.0

(AAtrex®) 4 L

Mineral 2.0–4.0 pt.

Muck 4.0–6.0 pt.

(AAtrex® Nine-0®) 90 WDG

Mineral 1.1–2.2 lb.

Muck 2.2–3.3 lb.

Germinating broadleaf and grass weeds. Apply to moist soil. Do not exceed 2.5 lb. a.i./A per calendar year. Consult label for plant-back restrictions on rotational crops.

Carfentrazone

0.008–0.016

(Aim®) 1.9 EW or 2 EC

0.5–1.0 fl. oz.

Emerged broadleaf weeds. Apply as a preplant burndown. Use a crop oil concentrate (COC) or nonionic surfactant (NIS) at recommended rates. Do not apply more than 2.0 fl. oz./A per season, including preplant burndown and crop application.

Dimethanamid- P

0.56–0.84

(Outlook®, Slider®) 6 EC

12–18 fl. oz.

Annual broadleaf and grass weeds. After application, incorporate into soil by rainfall, sprinkler irrigation, or mechanical tillage. Consult label for rate based on soil texture.

EPTC

4.0–6.0

(Eradicane®) 6.7 E

4.75–7.33

Annual broadleaf and grass weeds and purple/yellow nutsedge. Use lower rates on lighter soils (sand). Control of perennial weeds, such as bermudagrass or nutsedge, is increased with thorough incorporation.

Flufenacet

0.49–0.68

(DefineTM DF) 60 DF

13–18 oz.

(DefineTM SC) 4 SC

15–19 fl. oz.

Annual broadleaf and grass weeds. Rainfall, irrigation, or light cultivation is required within 7–10 days of application. Consult label for rate based on soil texture.

Glyphosate

0.3–1.0

(Various formulations)

Consult labels

Emerged broadleaf and grass weeds. Apply as a preplant burndown. Tank mix with a residual herbicide to broaden spectrum of weed control. Consult label for individual product directions.

Mesotrione

0.188–0.24

(Callisto®) 4 L

6.0–7.7 fl. oz.

Annual broadleaf weeds. Tank mix with a preemergence grass herbicide for grass control. Do not exceed 7.7 fl. oz./A per season.

S-metolachlor

1.0–1.6

(Dual Magnum®, BrawlTM) 7.62 EC

1.0–1.67 pt.

(Dual II Magnum®, Cinch®) 7.64 EC

1.0–1.67 pt.

Annual broadleaf and grass weeds. Use a lower rate on lighter soils. Weed control is increased with 0.5–1 in. of rainfall or irrigation. Do not exceed 3.9 pt./A per crop year depending on soil texture.

Paraquat

0.5–1.0

(Gramoxone®) 2 SL

2.0–4.0 pt.

(Firestorm®) 3 SL

1.3–2.7 pt.

Emerged broadleaf and grass weeds. Apply as a preplant burndown. No more than three applications per year. Tank mix with a residual preemergence herbicide to broaden the spectrum of weed control.

Pendimethalin

Mineral

0.75–1.0

Muck

1.0–2.0

(AcumenTM, Prowl®) 3.3 EC

Mineral 1.8–2.4 pt.

Muck 2.4–4.8 pt.

(Prowl® H20)

Mineral 2.0–3.0 pt.

Muck 2.0–4.0 pt.

Broadleaf and grass weeds. Overhead irrigation or rainfall is required within 7 days of application.

Pelargonic Acid

(Scythe®) 4.2 EC

3%–10% v/v

Emerged broadleaf and grass weeds. Apply as a preplant burndown treatment. Product is a contact, nonselective, foliar-applied herbicide with no residual control. May be tank mixed with soil residual compounds.

Simazine

2

(Princep®, Simazine) 4 L

2 qt.

(Princep®, Simazine) 90 WDG

2.2 lb.

Broadleaf and grass weeds. If a second application is required, do not exceed 2.5 lb. a.i./A per calendar year. Simazine 4L and Simazine 90 DF can be applied to muck soils at 2.5 lb. a.i./A. PHI 45 days.

Table 2. 

Postemergence weed control in sweet corn

Active ingredient

lb. a.i./A

Trade name

Amount of product/A

Weeds controlled / Remarks

Atrazine

Mineral

1.0–2.0

Muck

1.0–2.0

(AAtrex®) 4 L

Mineral 2.0–4.0 pt.

Muck 2.0–4.0 pt.

(AAtrex® Nine-0®) 90 WDG

Mineral 1.1–2.2 lb.

Muck 1.1–2.2 lb.

Broadleaf and some grass weeds. Apply before weeds exceed 1.5 in. in height and before corn exceeds 12 in. in height. Do not exceed 2.5 lb. a.i./A per calendar year. Consult label for plant-back restrictions on rotational crops.

Bentazon

0.75–1.0

(Basagran®) 4 L

1.5–2.0 pt.

Certain broadleaf and sedge weeds. Consult label for weeds controlled/weed size table. Do not apply more than 4 pt./A per season.

Carfentrazone

0.008–0.016

(Aim®) 1.9 EW or 2 EC

0.5–1.0 fl. oz.

Emerged broadleaf weeds. Apply up to the 14-leaf stage of corn growth. After the V8 stage of growth, apply as a directed application. Do not apply more than 2.0 fl. oz./A per season, including preplant burndown and crop application. PHI 3 days.

Clopyralid

0.15–0.23

(Clopyr Ag) 3 EC

0.3–0.6 pt.

Emerged broadleaf weeds. Apply after emergence and before corn is 18 in. tall. Consult label for plant-back restrictions on rotational crops. PHI 30 days.

Halosulfuron

0.03–0.05

(Sandea®) 75 DF

0.6–1 oz.

Broadleaf and nutsedge weeds. Apply over the top or with drop nozzles from the spike to the layby stage of corn. A sequential application of 2/3 oz./A may be with drop nozzles to avoid application to the plant whorl. No more than two applications per year.

Mesotrione

0.094

(Callisto®) 4 L

3 fl. oz.

Broadleaf weeds. Treat up to 30 in. tall or up to the eight-leaf stage. Include a crop oil concentrate (COC) or nonionic surfactant (NIS) in the spray solution. Slight leaf bleaching may occur. Do not exceed 7.7 fl. oz./A per season.

S-metolachlor

Up to 1.9

(Dual Magnum®, BrawlTM) 7.62 EC

Up to 2.0 pt.

(Dual II Magnum®, Cinch®) 7.64 EC

Up to 2.0 pt.

Annual broadleaf and grass weeds. Apply after crop emergence up to 40 in. in height. Direct spray to the base of the plants when plants are taller than 5 in. Use a lower rate on lighter soils. Weed control is increased with 0.5–1 in. of rainfall or irrigation. Do not exceed 3.9 pt./A per crop year depending on soil texture. PHI 30 days.

Nicosulfuron

0.03–0.06

(Accent®) 75 WDG

0.6–1.3 oz.

(Accent® Q) 54.5 WDG

0.9–1.8 oz.

Broadleaf and grass weeds. Sensitivity to sweet corn varieties is variable. Do not apply to 'Merit' sweet corn. Do not apply to corn that has previously been treated with Counter®, Lorsban®, or Thimet® insecticides because this may result in injury. Consult label for acceptable insecticides. Apply broadcast to corn plants less than 12 in. tall. Apply with drop nozzles to direct spray to corn plants 12– 8 in. tall.

Pendimethalin

Mineral

0.75–1.0

Muck

1.0–2.0

(AcumenTM, Prowl®) 3.3 EC

Mineral 1.8–2.4 pt.

Muck 2.4–4.8 pt.

(Prowl® H20)

Mineral 2.0–3.0 pt.

Muck 2.0–4.0 pt.

Broadleaf and grass weeds. Apply after 4 in. tall until corn is 20–24 in. tall or the V8 growth stage. Direct the spray to the base the plants.

Tembotrione

0.08

(Laudis®) 3.5 EC

3 fl. oz.

Annual broadleaf and grass weeds. Crop tolerance is dependent on variety, so apply to a small area if tolerance is unknown. Do not use on 'Merit' or 'Shogun' varieties. May be applied from corn emergence through the V7 stage of growth. Do not exceed 3 fl. oz./A per season.

Topramezone

0.02–0.022

(Impact®) 2.8

0.75–1 fl. oz.

Broadleaf and grass weeds. Consult label for maximum size of certain weed species for control. PHI 45 days.

Footnotes

1.

This document is HS197, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 1993. Revised December 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Peter J. Dittmar, assistant professor, and William M. Stall, emeritus professor, Horticultural Sciences Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others 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.