Dimethyl Disulfide (DMDS) · Pacific Ag Group, Arroyo Grande, CA - 2005 (Weed Counts/row) 0 1530...

Dimethyl Disulfide (DMDS)A Methyl-Bromide Replacement Candidate

P. Robinson, R. Whitson, & T. Estes

Natural Background Concentrations

Biological1Human expired air: max. 0.6 μg/hr)Human expired air: max. 7ng/l)Poultry manure: 85 μg/kg

Anthropogenic1

Wastewater effluent (45 μg/l)

1/ low levels are maintained due to flux

• Living Organisms• Salt Water• Brackish Water• Fresh Water• Sediment• Soil• Atmosphere

Naturally Occurring in the Environment

Formation From Natural Processes

Biogenic Atmospheric Sulfur Cycle

Methionine Degradation Pathwaycheese products

Dimethylsulfoniopropianate (DMSP) Degradation Pathway

marine bacteria

DMDS: An ubiquitous natural compound

In plants •Allium spp

• pea bean

•Brassicacea spp

• mushrooms (truffle, shiitake)

In animal tissues • milk cheese • human urine

• animal by-products

In processed food• coffee bread salmon

• registered as a food additive to create a garlic-like taste

In Brassicacea:from thiomethyl glucosinolatesGlu-S

-O3SO

N

(CH2)n-S(O)x-CH3

n = 2, 3, …10x = 0, 1, 2

Glu-S

-O3SO

NN

(CH2)n-S(O)x-CH3

n = 2, 3, …10x = 0, 1, 2

Glucosinolates

CH3-SO-(CH2)n-N=C=S

Isothiocyanates

CH3-S-SO-CH3

Thiosulfinates

CH3-S-SO2-CH3 + CH3-S-S-CH3

Thiosulfonates

mirosinase

Pathways for the formation of DMDS

In Allium spp.From S-methyl-cysteine sulfoxide

S-methyl-cysteine sulfoxide

CH3-S-SO-CH3

Thiosulfinates

CH3-S-SO2-CH3 + CH3-S-S-CH3

Thiosulfonates

NH2-CH(COOH)-CH2-S(O)-CH3

alliinase

Pathways for the formation of DMDS

Ozone depleting potential (ODP) is 0

Half-life in the upper atmosphere predicted to be on the order of several hours

Part of the natural atmospheric sulfur cycle with formation of acidic sulfur products

DMDS Atmospheric Effects

Important Industrial Uses of DMDS• Agent used in hydrodesulfurization

processes in the petrochemical industry

• Coke inhibiting agent used in ethylene furnaces

• Used as an FDA registered food additive

• (Sec. 172.515 Synthetic flavoring substances and adjuvants) for flavoring use “in the minimum quantity to produce their intended effect”

DMDS physical-chemical properties

Molecular formula: C2S2H6Molecular weight: 94.201Appearance: yellow liquidOdor: garlic-like smell


Boiling point: 109.8° CFlash point: 16° CDensity 1.0625 (20° C)Henry’s law constant: 1.21-3 (20° C)


Koc 15-47 mL/gVapor pressure: 28.7 mm Hg (25° C)Water solubility: 3000 mg/L (25° C)

DMDS causes mitochondrial dysfunctionand activation of K-ATP channels

blocks the cytochrome oxydase (Complex IV)acts on K-ATP channels by an hyperpolarization

DMDS Mode of Action

Acute Toxicity ProfileAcute oral LD50- rats: 150 – 240 mg/kg

Acute inhalation LC50- rats: 776 - 835 ppm (2988 – 3215 mg/m3)

Acute dermal LD50- rabbits: >2000 mg/kg

Dermal irritation: Irritant (Tox. Category III)

Eye irritation: Irritant (Tox. Category III)

Dermal sensitization: Non-sensitizer

DMDS EfficacyWeed Control

DMDS EfficacyRate Response

% Control of Nutsedge in Peppers W/ DMDS Applied Alone Under LDPE, Rate Effect Vs. Methyl Bromide.Culpepper, Univ. Georgia, Tifton 2005

30

79

90100

0

10

20

30

40

50

60

70

80

90

100

DMDS 200 DMDS 400 DMDS 600 MeBr 400 (67:33)

% Nutsedge control at 34 Days After Application

Rates in Lbs/Acre

DMDS EfficacyApplication Depth

Effect of Injection Depth & Barrier Type on Weed Control

VIFLDPE

12”12”

8” 8”

DMDS @ 62 gallons/acre (79:21)

DMDS EfficacyInjection Shank Number

Nutsedge Control in Tomato, DMDS Alone, Shank Number EffectLDPE, VIF, Vs. METALIZED FILM Gilreath, Univ. Florida, Ruskin, FL 2005 Fall

0

50

100

150

200

250

300

350

400

LDPE VIF METAL

14 day plantback interval, weed control at 74 Days after application

Counts (50 ft.) area3-shank injection

4-shank injection

DMDS @ 400 lb/A

DMDS EfficacyBarrier Type

Nutsedge Control in Tomato, DMDS Alone, Barrier EffectLDPE, VIF, Vs. METALIZED FILM Gilreath, Univ. Florida, Ruskin, FL 2005 Fall

0

100

200

300

400

500

600

700

LDPE VIF METAL

14 day plantback interval, weed control at 49 Days after application

Cou

nts

(50

ft.) a

rea

UNTREATED

DMDS @ 400 lb/A

60 65 70 75 80 85 90 95 100

LDPE (w/b)

LDPE (w/w/)

VIF (b/b)

METAL Embossed (b/s)

METAL Embossed (s/b)

METAL (s/w)

METAL (s/b)

DMDS 750 (80:20)

Trial conducted by Dr. Stanley Culpepper; UGA REC; Tifton, GA. All treatments applied on 7/14/05. Squash were planted 27 days after fumigant applications. Evaluations at 47 days after Planting

DMDS on Squash, % Nutsedge Control in Tifton; GA; Fall 2005 Mulch Type Effect, DMDS Mixture With Chloropicrin

Combinations of DMDS With Chloropicrin

Effect of Rate and Combinations With Chloropicrin on Nutsedge Control (%), Culpepper. Univ. GA, Tifton, 2005

0

20

40

60

80

100

Alone + PIC @ 100lbs.

+ PIC @ 200lbs.

MeBr @ 400(67:33)

Percent Nutsedge Control @ 97 Days After Application, LDPE Barrier

DMDS @ 200 lbs. DMDS @ 400 lbs. DMDS @ 600 lbs.

The Overall Influence of These Variables on Weed Control

DMDS 79:21 @ 74 gal570 lb. DMDS: 150 PIC

UNTREATED

LDPE

% Control of Nutsedge in Peppers w/ DMDS + PICBarrier Comparisons Culpepper, Univ. Georgia, Tifton 2006


UNTREATED

VIF



UNTREATED

METALIZED


0

25

50

75

100

LDPE METALIZED VIF

UNT DMDS 75 gal (79:21) MEBR 350 (67:33)

Trial conducted by Dr. Stanley Culpepper; UGA REC; Tifton, GA. All treatments applied on 2/22/06. Holes were punched in mulch 15 days after application and peppers were planted 3 days later.

% Control of Nutsedge at 72 days after application

Impact of Mulch Types on Nutsedge Control of the Untreated,MeBr &DMDS Treatments; Tifton; GA; Spring 2006

DMDSCrop Safety

Excellent Crop Safety

Plant back in 7-21 day

0

10

20

30

40

50

60

70

LDPE METALIZED VIF

UNT DMDS 75 gal (79:21) MEBR 350 (67:33)

Number of Fruit/Plot: Harvests 1 & 2 combined


Impact of Mulch Types on Marketable Pepper Yields of the Untreated, MeBr &DMDS Treatments; Tifton; GA; Spring 2006

0

5

10

15

20

25

LDPE METALIZED VIF

UNT DMDS 75 gal (79:21) MEBR 350 (67:33)

Pounds of Fruit/Plot: Harvests 1& 2 combined


Impact of Mulch Types on Marketable Pepper Yields of the Untreated, MeBr &DMDS Treatments; Tifton; GA; Spring 2006

Drip Vs Shank Effect

0

5

10

15

20

25

UntreatedControl

DMDS @ 400lbs - Drip

Pic @ 200 lbs- drip

DMDS + Pic @ 200+200 -

Drip

MB + Pic(67:33) @ 350

lbs - shank

70 DAA

WEED BIOMASS (Kg/PLOT)

DMDS Drip Application Efficacy in Strawberry, Weed Biomass

San Luis Obispo, CA 2005 Pacific Ag GroupApplication: 11/10/05. Harvest From: Jan to May

Effect on Additional Weed Species

DMDS – TomatoPacific Ag Group, Arroyo Grande, CA - 2005 (Weed Counts/row)

0 20 40 60 80Weed Control - 34 Days After Application

DMDS 400 -Drip

DMDS 600 - Drip

Weed Control (counts/row)

Purslane Corn Spurry Lambsquarters Annual Bluegrass Nutsedge


0 20 40 60

Weed Control - 34 Days After Application

DMDS 400 -Drip

DMDS 600 - Drip

DMDS + Pic 200 +200 - Drip




DMDS alone & w/PIC


0 15 30 45 60 75

Weed Control - 34 Days After Application




DMDS + Pic 400 +200 Shank

DMDS + Pic 600 +200 Shank


DMDS alone & w/PIC,

Shank vs. drip

DMDS EfficacySoil Borne Pathogens

Tomatoes, Drip ApplicationPacific Ag Group – Greenfield, CA - 2004

0

2

4

6

8

10

Scle

rotin

ia #

/plo

t

Untreated DMDS @200 lbs.

DMDS @400 lbs.

DMDS @600 lbs.

Inline @ 20Gal/A

MethylBromide

@ 350 lbs.

Sclerotinia Rot (Scleotinia sclerotiorum )

Rated at harvest (119 days after application).

Tomatoes, Drip ApplicationPacific Ag Group – Greenfield, CA - 2004

0

2

4

6

8

10

0-10

sca

le

Untreated DMDS @200 lbs.

DMDS @400 lbs.

DMDS @600 lbs.

Inline @ 20Gal/A

MethylBromide @

350 lbs.

Corky Root (Pyrenochaeta lycopersici )

Succulent Beans & Disease Incidence France, 2003

05

10152025

30354045

50

% in

fect

ed p

lant

s

Untreated DMDS @ 267 lbs. DMDS @ 535 lbs. Methyl Bromide @446 lbs.

Rhizoctonia solani

DMDS – Tomato Verticillium WiltPacific Ag Group, Arroyo Grande, CA - 2005

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Num

ber p

er P

lot

Verticillium Wilt Infected Plants - 125 days after application

Untreated Control DMDS 400 - Drip DMDS 600 Drip Chloropicrin 200 - Drip

DMDS – Tomato Verticillium WiltPacific Ag Group, Arroyo Grande, CA - 2005

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Num

ber p

er P

lot

Verticillium Wilt Infected Plants - 125 days after application

Untreated Control DMDS + Pic 200 + 200 Drip DMDS + Pic 400 + 200 Drip

DMDS + Pic 600 + 200 Drip Chloropicrin 200 - Drip

IRIS – Plants with Fusarium WiltPacific Ag Group, Nipomo, CA - 2005

0

5

10

15

20

25

30

Num

ber/P

lot

121 Days After Application

Untreated Control MB + Pic fb Vapam VapamChloropicrin @ 200 lbs DMDS + Pic @ 400 + 200 DMDS + Pic @ 600 + 200

DMDS EfficacySoil Borne Pathogens

Sclerotinia Rot

Rhizoctonia

Verticillium Wilt

Fusarium Wilt

Pythium?

DMDS EfficacyNematodes

Soil Borne Pest Control in Tomatoes Shank Application on 3-mar, 2004

Pliant High Barrier Mulch (Black)J. Gilreath, Univ. FL Bradenton

0

1

2

3

4

Nem

atod

es/1

00cc

of s

oil

7-Jun

Number of Stunt Nematodes (Tylenchorhynchus sp. )

Untreated

DMDS @ 200 lb/A

DMDS @ 400 lb/A

DMDS @ 600 lb/A

Midas @ 300 lb/A

Midas is methyl iodide:chloropicrin (67:33)

Root Gall Severity in Tomato (0-10 Scale)

0

2

4

6

8

10

Alone + PIC @ 100

<---B

est -

Wor

st---

>

Untreated DMDS 150 DMDS 300DMDS 450 DMDS 600 Telone C35 @ 26 GPAMeBr 400 (67:33)

Meloidogyne sp.

J. Noling, Univ. of Florida @ Lake Alfred, FL 2005, fall

DMDS – TomatoPacific Ag Group, Arroyo Grande, CA - 2005

0

50

100

150

200

250

Num

ber

per

Cub

ic

Cen

timet

er

Stubby Root Nematode - 67 DAT - Compared to UTC

Untreated Control DMDS 400 - Drip DMDS 600 DripDMDS + Pic 200 + 200 Drip DMDS + Pic 400 + 200 Drip DMDS + Pic 600 + 200 DripDMDS + Pic 400 + 200 Shank DMDS + Pic 600 + 200 Shank Chloropicrin 200 - DripVapam - 75 gal - Drip Inline 20.5 gal - Drip Midas + Pic 120 + 240 -Drip

Paratrichodorus sp.

DMDS – TomatoPacific Ag Group, Arroyo Grande, CA - 2005

05

101520253035

Num

ber p

er C

ubic

C

entim

eter

Root Lesion Nematode - 67 DAT

Untreated Control DMDS 400 - Drip DMDS 600 DripDMDS + Pic 200 + 200 Drip DMDS + Pic 400 + 200 Drip DMDS + Pic 600 + 200 DripDMDS + Pic 400 + 200 Shank DMDS + Pic 600 + 200 Shank Chloropicrin 200 - DripVapam - 75 gal - Drip Inline 20.5 gal - Drip Midas + Pic 120 + 240 -Drip

Pratylenchus spp.

DMDS Efficacy Against Citrus Nematode Application Via Buried Drip at 8” Depth. Radewald, CA-2006.

0

500

1000

1500

2000

2500

3000

3500

4000

6"depth 10"depth 18"depth

Untreated DMDS @ 141 lb/A-no barrierDMDS @ 290 lb/A-no barrier DMDS @ 290 lb/A-w/LDPEDMDS @ 581 lb/A-no barrier DMDS @ 581 lb/A-w/LDPE

Number of nematodes recovered from bags buried at each depth

DMDS EfficacyNematodesStunt

Root Knot

Stubby

Lesion

Cyst?

DMDS Registration

Submission for an EUP programAugust, 2006Currently in science review

Submission for Section 3 registration1st quarter, 2007

DMDSDMDS effective in shank and drip applications (pure and 95% EC formulations)

On nematodes (200/400 kg.ha-1)On fungi (400/600 kg.ha-1)On weeds (600 kg.ha-1)

Soil diffusion is very goodEffectiveness is higher using VIF or equivalent filmsDMDS in combination with chloropicrin demonstrates excellent results, lower rates

DMDS is a viable candidate for replacement for Methyl Bromide

Thank you!

Dimethyl Disulfide (DMDS) · Pacific Ag Group, Arroyo Grande, CA - 2005 (Weed Counts/row) 0 1530...

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