Postemergence Contact Herbicides Organic and Other Non-microbial

Cheryl Wilen University of California Cooperative Extension/UC IPM

Joe Neal

North Carolina State University

Treatments and Rates

Suppress*+ Warning 32% capric acid 47% caprylic acid 6% WESTBRIDGE WeedPharm/ others* Danger 20% acetic acid neat Pharm Solutions

Avenger/S3/AG* Caution 89/55% limonene 14% INNVICTIS CROP CARE

CUTTING EDGE FORMULATIONS

AXXE* Warning 40% ammonium nonanoate 6% BIOSAFE SYSTEMS

WeedZap* 25 (b) 45% clove oil 45% cinnamon oil 5% JH Biotech

Burnout II* Danger 8% clove oil 24% citric acid 25% Bonide

Scythe Warning 3% nonanoic acid, other related 57% nonanoic acid 5% GOWAN

Fiesta** Caution 26.52% iron hedta 4% ENGAGE AGRO

FinalSan* Warning 22% free fatty acids and/or amine salts 16.7% ENGAGE AGRO

/NEUDORFF

*organic or listed as “organic” on label **biopesticide +acidified to pH6

Modes-of-action HRAC GROUP: Z

WSSA Group: 17, 27

• All are contact, POE, non-systemic ,generally non-selective

• Most are considered desiccants, likely due to degradation of cuticular wax but possibly rapid dissolution of cell membrane integrity

• Fe HEDTA - iron toxicity (oxidative damage) at the cellular level leading to tissue necrosis

• Resistance management considerations – likely a non-issue

Use Sites and Targets • Around nurseries, greenhouses, landscapes,

food crops and non crop areas, under trees in orchards, row middles (turf – Fe HEDTA)

• Labels often include: grasses, vines, underbrush, annual/perennial plants, bryophytes, suckers

• Functionally: Primarily young annual broadleaves, seedling grasses, very young seedling perennials

Results Both spray volume and conc. were highly significant, but interaction was not significant (white clover)

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Spray Volume (L ha-1) Wolfe, Neal, Harlow

Results However, there were no differences between treatments receiving the same dose of FeHEDTA per unit area

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Spray Volume (L ha-1) Wolfe, Neal, Harlow

Integrated programs vs stand alone trials

• Could not be certain whether volume and concentration have an effect on FeHEDTA efficacy independent of dosing.

• Consisted of a full factorial of three spray volumes and four doses of FeHEDTA, plus a non-treated

Results FeHEDTA dose was found to be significant, while volume was not significant.

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FeHEDTA Rate (kg ai ha-1)

Wolfe, Neal, Harlow

Application intervals to maximize efficacy on hard-to-control weeds

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Weeks After Treatment

A: 29.7 kg/ha 2w

B: 29.7 kg/ha 3w

C: 59.4 kg/ha 2w

D: 59.4 kg/ha 3w

A + C App 2

B + D App 2

A + C App 3 B + D

App 3

Wolfe, Neal, Harlow

Henbit

8004E 40PSI CO2 backpack Applied 8/22/2016 and 9/10/16 842 L/ha [90GPA] 4 reps CRD

Liberate 0.5% Most seedlings in cotyledon stg (1st app)

Herbicide+0.5% Liberate

UTC

Herbicide

1.52m

1.52m

1.52m

Avenger

7dat1 10dat2 Weed size

Finalsan

7dat 10dat2 Adjuvant

Fiesta

7dat1 10dat2

Excellent hairy fleabane activity

August 2016 Cost/1000Ft2

Roundup Pro Caution 48.7% glyphosate $69.99 2.5 gal $0.87

Suppress Warning 32% capric acid 47% caprylic acid $150 2.5 gal $7.49

Finale Warning 11.33% glufosinate-ammonium $175 2.5 gal $2.17

WeedPharm Danger 20% acetic acid $29.95 gal $7.80

AvengerAG Caution 55% limonene $157.26 2.5 gal $18.53

AXXE Warning 40% ammonium nonanoate $195.02 2.5 gal $9.68

WeedZap 25 (b) 45% clove oil 45% cinnamon oil $124.35 gal $12.84

Burnout II Danger 8% clove oil 24% citric acid $135.00 2.5 gal $27.91 Scythe Warning 3% nonanoic acid, other related 57% nonanoic acid $178.98 2.5 gal $7.39

Fiesta Caution 26.52% iron hedta $250.95 2.5 gal $8.15

FinalSan* Warning 22% free fatty acids and/or amine salts $94 2.5 gal $12.94

*w/surfactant is much better

August 2016 Cost/1000Ft2

Roundup Pro Caution 48.7% glyphosate $69.99 2.5 gal $0.87

Suppress Warning 32% capric acid 47% caprylic acid $150 2.5 gal $7.49

Finale Warning 11.33% glufosinate-ammonium $175 2.5 gal $2.17

WeedPharm Danger 20% acetic acid $29.95 gal $7.80

AvengerAG Caution 55% limonene $157.26 2.5 gal $18.53

AXXE Warning 40% ammonium nonanoate $195.02 2.5 gal $9.68

WeedZap 25 (b) 45% clove oil 45% cinnamon oil $124.35 gal $12.84

Burnout II Danger 8% clove oil 24% citric acid $135.00 2.5 gal $27.91 Scythe Warning 3% nonanoic acid, other related 57% nonanoic acid $178.98 2.5 gal $7.39

Fiesta Caution 26.52% iron hedta $250.95 2.5 gal $8.15

FinalSan* Warning 22% free fatty acids and/or amine salts $94 2.5 gal $12.94

*w/surfactant is much better

Considerations • Volume vs Rate [nozzles?] • Intervals • Adjuvants • pH • Dormant crop vs Actively growing • Weed stage/size • Weed spectrum • Sunlight • Temperature (Fall/Winter vs Spring/Summer)

Errata What ever happened to:

– “Manuka Oil, A Natural Herbicide with Preemergence Activity,” Weed Science, Vol. 59, No. 4, October-December 2011

– Mustard Meal as PRE

Review – Bioherbicides in Organic Horticulture (2016)

Xiaoya Cai and Mengmeng Gu see “Factors Affecting the Efficacy of Bioherbicide” section