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Publication #HS203

Weed Management in Leafy Greens (Lettuce, Endive, Escarole, and Spinach)1

Peter Dittmar and William Stall2

Optimal leaf crop production depends on successful weed control. Weeds reduce leaf crop yields by direct competition for nutrients, water, and light.

Weed control is especially important early in the growth of the crop. Competition from amaranth (spiney, common, or livid) weeds can cause 20%–40% yield reduction in lettuce if not controlled within 3–5 weeks of emergence. One spiney amaranth plant can reduce yield and quality of four lettuce plants in the row around it.

Effective weed control should include a combination of practices designed to suppress weeds during the entire year.

Management practices include crop rotation, cover cropping, cultivation flooding, and mulching. Crop rotation and flooding are routinely followed in Florida's more intensively cultivated organic soils. Care should be taken when leaf crops are rotated behind crops where more persistent herbicides were used. If carried out before planting, bioassays using indicator crops can save valuable time and problems by indicating if an herbicide persists in the soil.

Mulching should be considered for any lettuce grown in mineral soils. Colored mulches can increase or decrease soil temperature depending on the time of year. A labeled multipurpose fumigant may eliminate many soilborne insects, diseases, and weeds.

Cultivation in leaf crops is a necessity and is a detriment if not done properly.

In seeded lettuce, thinning and blocking usually are done at 21–28 days. Cultivation at this time is required to reduce any competition from weeds emerging in the row. Cultivation also prunes lettuce plant roots and in itself reduces subsequent quality and yield if special care isn't exercised. Cultivation in older lettuce has also been shown to reduce quality if carried out improperly.

Pursuit® is a third-party registration. For legal use of the herbicide, the grower (applicator) must obtain the label from the third-party registrant (in this case TPR, Inc., Orlando). Use of the product without having a signed authorization and waiver and limitation of liability agreement is a misuse of the product.

To reduce confusion, the EPA has recently defined tolerance terminology in lettuce. If a label states head lettuce, the pesticide may only be applied to the crisp head varieties of lettuce. If leaf lettuce is stated, this may be applied to all leaf lettuce types, including leaf lettuce, cos (Romaine), and butterhead varieties. The term "lettuce" includes head and leaf lettuce (i.e., all types except endive and escarole). Endive is a separate tolerance crop and includes endive and escarole.

The leafy greens group includes lettuce (head and leaf), endive, and spinach as well as amaranth, arugula (roquette), chervil, chrysanthemum, corn salad, garden and upland cress, dandelion, dock, orach, parsley, purslane (garden and winter), radicchio, New Zealand spinach, and vine spinach. A label for the "leafy greens" group includes all of these. If a label has the term "leafy vegetables," it is labeled for the leafy greens plus the leaf petiole (celery) group.

Figure 1. 

Henbit growing in romaine lettuce


Credit:

Peter Dittmar


[Click thumbnail to enlarge.]

Tables

Table 1. 

Preplant chemical weed control in leafy greens (lettuce, endive, escarole, and spinach)

Active ingredient

lb. a.i./A

(Trade name)

amount of product/A

Crops

Weeds controlled / remarks

Benefin

1.2

(BalanTM)

2.0

Lettuce

Annual broadleaf and grass weeds. Apply before seeding or transplanting. Incorporate with cultivation or irrigation into the top 2–3 inches of the final bed.

Bensulide

5–6

(Prefar®) 4 E

5–6 qt.

Leafy vegetables

Annual broadleaf and grass weeds. Incorporate with cultivation or irrigation. Do not use on spinach or Swiss chard.

Carfentrazone

Up to 0.031

(Aim®) 2.0 EC

Up to 2 fl. oz.

(Aim®) 1.9 EW

Up to 2 fl. oz.

Leafy vegetables

Emerged broadleaf weeds. Apply as a burndown herbicide before planting.

Glyphosate

(Various formulations)

Consult label

Leafy vegetables

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

Imazethapyr

0.016–0.031

(Pursuit®) 2

1–2 fl. oz.

Lettuce, endive, escarole

Broadleaf weeds. Apply in fields with 40% organic matter or greater. Do not make more than two applications per crop. A maximum of 4 oz. of product may be used per crop season. Should be applied in 2 or more gal. of water per acre. Potential for rotational crop damage is highly variable. Label is a third-party registration (TPR, Inc.). Use without having a signed authorization and waiver of liability agreement is a misuse of the product. PHI 30 days.

Paraquat

0.5–1.0

(Gramoxone®) 2 SL

2–4 pt.

(Firestorm®) 3SL

1.3–2.7 pt.

Lettuce

Emerged broadleaf and grass weeds. Apply as a preplant burndown. Do not make more than three applications per year.

Pelargonic acid

(Scythe®) 4.2 EC

3%–10% v/v

Leafy vegetables

Emerged broadleaf and grass weeds. Apply as a preplant burndown before planting.

Pronamide

1.0–2.0

(Kerb®) 50 WP

2.0–4.0 lb.

Head lettuce, endive, escarole

Certain annual broadleaf and grass weeds. Overhead irrigate with 1–2 inches following applications. Observe rotational restrictions to other crops. Not recommended for soils with high organic matter. PHI 55 days.

Pyraflufen

0.0008–0.003

(ET® Herbicide)

0.5–2.0 fl. oz.

Leafy vegetables

Emerged broadleaf weeds. Apply as a preplant burndown 1 day prior to planting. Include a nonionic surfactant at 0.25% or crop oil concentrate at 1.0% to the spray solution.

Trifluralin

0.5

(Treflan®, Trifluralin) 4 EC

1.0 pt.

(Trifluralin) 10 G

5 lb.

Endive, escarole, radicchio

Annual broadleaf and grass weeds. Apply as preplant incorporated to mineral soils only.

Table 2. 

Postemergence chemical weed control in leafy greens (lettuce, endive, escarole, and spinach)

Active ingredient

lb. a.i./A

(Trade name)

amount of product/A

Crops

Weeds controlled / remarks

Carfentrazone

Up to 0.031

(Aim®) 2.0 EC

Up to 2 fl. oz.

(Aim®) 1.9 EW

Up to 2 fl. oz.

Leafy vegetables

Emerged broadleaf weeds. Use a hooded/shielded sprayer to direct spray to the row middles only. Use a crop oil concentrate (COC) or nonionic surfactant (NIS). PHI 0 days.

Clethodim

0.094–0.125

0.07–0.125

(Select®) 2 EC

6–8 fl. oz.

Leaf lettuce

Emerged annual and perennial grass weeds. Allow a minimum of 14 days between repeated applications. PHI 14 days.

Clethodim

0.094–0.125

0.07–0.125

(Arrow®) 2 EC

6–8 fl. oz.

(Select Max®) 1 EC

9–16 fl. oz.

Leafy vegetables

Emerged annual and perennial grass weeds. Allow a minimum of 14 days between repeated applications. PHI 14 days.

Imazethapyr

0.016–0.031

(Pursuit®) 2

1–2 fl. oz.

Lettuce, endive, escarole

Broadleaf weeds. Apply in fields with 40% or greater organic matter. Apply postemergence after three to four true leaf stage. Do not make more than two applications per crop. A maximum of 4 oz. of product may be used per crop season. Apply in 2 or more gal. of water per acre. Potential for rotational crop damage is highly variable. Label is a third-party registration (TPR, Inc.). Use without having a signed authorization and waiver of liability agreement is a misuse of the product. PHI 30 days.

Pelargonic acid

(Scythe®) 4.2 EC

3%–10% v/v

Leafy vegetables

Emerged broadleaf and grass weeds. Apply as a directed or shielded spray to row middles.

Sethoxydim

0.19–0.28

(Poast®) 1.5 EC

1.0–1.5 pt.

Head/leaf lettuce, endive, radicchio

Emerged grass weeds. Do not exceed 3.0 pt./A per season. Include a COC at 2 pt. per 5–20 gal. of water. Head lettuce and radicchio PHI 30 days. Leaf lettuce and endive PHI 15 days.

Footnotes

1.

This document is HS203, 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 August 2003. Revised April 2013. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Peter Dittmar, assistant professor, and William 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 product named, and does not signify that they are approved to the exclusion of others of suitable composition.7.1.


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.