MEMORANDUM 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

JUN 2 4 Z0\3 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile (BCP) for Registration Review of Dimethyl Disulfide 

FROM: 

THRU: 

TO: 

(029088) 

Leonard Y ourman, Plant Pathologist 

Biological Analysis Branch 

Jihad Alsadek, Economist vr ;;w k"..._ lt.J~-~-.f.ei~. Science Information and Analysis Branch 

Derek Berwald, Economist ~( ~ \fl./\ ( ,· 

Economic Analysis Branch \j ) v,. \~ 

Biological 

Arnet Jones, 

Analysis 

Chief 

BrancH u ~ '-

Diann Sims, Chief JOt~ 

.. 

Science Information and Analysis Branch ~ 

Timothy Kiely, Chief ~ Vv\_ 

Economic Analysis Branch \._..I V 

Biological and Economic Analysis Division (7503P) 

Garland Waleko, Chemical Review Manager 

Risk Management and Implementation Branch 4 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: June 12, 2013 

INTRODUCTION 

The purpose of this BEAD Chemical Profile (BCP) is to convey usage information and a broad 

overview of the pest management roles of pesticides that are beginning to undergo registration 

review. The anticipated audience consists of the team of EPA staff currently evaluating the 

registration status of dimethyl disulfide and eventually the general public. This document builds 
upon the data provided by BEAD in the usage and label use data packages that are also provided 

to Registration Review teams. The document is based on information and data available to 

BEAD as of May, 2013. 

Dimethyl disulfide (DMDS) is formulated as a soil fumigant targeting a spectrum of soil 

inhabiting pests including weeds (e.g., nutsedge, chickweed, lambsquarters, purslane, various 

grasses), nematodes (e.g., root knot, stubby root, lesion, stunt, sting), and pathogens (e.g., 

Verticillium, Fusarium, Pythium, Sclerotinia, Rhizoctonia). DMDS has a distinctive and strong 

odor likened to potent garlic or decomposing biological materials (EPA, 201 0). 

COMMON FORMULATIONS AND APPLICATION METHODS 

DMDS (Paladin~ is formulated as emulsifiable and soluble concentrates. DMDS is applied in 

drip irrigation systems, shank injection to raised beds, and as a broadcast shank application. It is 

commonly co-applied with chloropicrin (21%) and may be co-applied with other fumigants such 

as 1,3-dichloropropene (1,3-D) or metam-sodium as specified on DMDS labels to enhance 

activity against a wider array of pests. Tarps must cover areas treated with DMDS. Tarps 

generally enhance the efficacy of a fumigant and for DMDS, can help reduce the potent odor 

after application. 

USE SITES 

Agricultural Use Sites 

DMDS is lalfeled to fumigate soils used for growing small berries (blueberry, strawberry), 

cucurbits (cucumbers, melons, squash), and fruiting vegetables (tomato, pepper, eggplant). 

Non-agricultural Use Sites 

DMDS is registered for use on field grown ornamentals, and forest tree nursery. 

USAGE 

There is no reported usage information for DMDS. This chemical, first registered for use in 

some states in July of2010, is used as a pre-plant fumigant in soil to control or suppress 

nematodes, various soilborne pathogens, nematodes, and weeds in fields in which berries, 

cucurbits, and fruiting vegetables will be grown. DMDS is not registered in California. DMDS 

(which may be co-applied with chloropicrin or other fumigants to enhance efficacy) is 

considered a methyl bromide alternative where data show efficacy for particular use sites. 

BIOLOGICAL ASPECTS RELEVANT TO DIMETHYL DISULFIDE 

DMDS has been studied in experimental field trials in order to identify effective rates and 

methods of application. However, odor from soils treated with DMDS appears to be of concern 

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to growers and reduces the incentive to use DMDS on land in proximity to residential areas. 

Generally, DMDS has shown efficacy in field trials against some pests, and generally, has been 

shown to provide comparable efficacy to methyl bromide. For example, in Florida vegetable 

trials to identify methyl bromide alternatives, DMDS with chloropicrin (21 %) provided good to 

excellent control of nematodes and pathogens, and excellent control of nutsedge (but poor 

control of annual grasses, which required an additional herbicide application) (No ling et al., 

2012). In Georgia, trials were conducted to assess the efficacy of a DMDS mixture or coapplication with chloropicrin and 1 ,3-dichloropropene against nutsedge in tomato and pepper 

production (Culpepper et al., 2012). The objective of the multi-season study is to provide easy 

application, low buffer restrictions, minimal odor, acceptable costs, and efficacy comparable to a 

standard 50:50 formulation of methyl bromide:chloropicrin. The results based on two seasons of 

data showed that the objectives of the study were obtainable. Further trials are being conducted, 

in 2013, to improve pest management and further reduce costs. In cut flower trials in Florida, 

DMDS formulations were found to provide good weed, nematode, and disease control and 

comparable to methyl bromide treatments (Rosskopf et al., 2012). In Michigan cucurbit field 

trials with soil infested with the pathogen Phytophthora capsici DMDS:chloropicrin (79:21) 

provided yields similar or greater than cucurbit soils treated with methyl bromide:chloropicrin 

(67:33) (Hausbeck et al., 2012) . 

. ROLE OF DMDS IN PEST CONTROL 

In 2009, BEAD evaluated a request for a finding that a conditional registration was in the public 

interest (Y ourman, 2009). The findings indicated that DMDS, especially when used in 

combination with other fumigants (typically chloropicrin, as discussed above), may be an 

important alternative to methyl-bromide for pre-plant soil fumigation, and therefore, its potential 

value to growers is high. DMDS is a likely alternative to other important fumigants such as 1,3-

D whose use may be limited due to label restrictions, such as in karst formations in Florida. 

Currently DMDS is not registered in California, but if there is a future registration, DMDS 

would likely be an important alternative to 1,3-D, which has caps on its overall use in 

agricultural townships. Since the voluntary cancellation of iodomethane the value of DMDS as a 

fumigant may be even more important for growers as a methyl-bromide alternative. However, 

widespread adoption of DMDS would likely require addressing its odor problem possibly 

through innovative application methods. A registration in California would also likely increase 

the use of DMDS. 

INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

DIMETHYL DISULFIDE 

BEAD has no usage data for DMDS. While results of experimental trials have been published, 

information on commercial use of DMDS and comparative efficacy would be helpful for any 

issues that might need to be addressed in registration review. In addition, cost data and 

geographical use information can be important to evaluating the benefits of DMDS. 

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REFERENCES 

Culpepper, S., Upchurch, W., and Fuller, P. 2012. WSP (TE-3): A potentially new fumigant 

system. International Research Conference on Methyl Bromide Alternatives and Emissions 

Reductions (2012). http://mbao.org/2012/Proceedings/28CulpepperS.pdf [Accessed June 3, 

2013] 

EPA. 2010. Pesticide Fact Sheet-Dimethyl Disulfide. July 9, 2010. 

http://www.epa.gov/pesticides/chem search/reg actions/pending/fs PC-029088 09-Jul-1 O.pdf 

Hausbeck, M. K., Enzenbacher, T. B., Cortright, B. D., and Linderman, S. D. 2012. 

Phytophthora and fumigation. Michigan State University Extension. 

http://veggies.msu.edu/Research!FS FumigationPcap.pdf [Accessed June 3, 2013] 

Noling, J. W., Botts, D. A., and MacRae, A. W. 2012. Alternatives to methyl bromide soil 

fumigation for Florida vegetable production. University of Florida Extension, 2012-2013, 

Vegetable Production Handbook, pg. 47. Document HS710. 

http://nfrec.ifas.ufl.edu/Vegetable Production/2012 VPG main6.pdf [Accessed June 3, 2013] 

Rosskopf, E. N., Kokalis-Burelle, N., McSorley, R., and Skvarch, E. 2012. Optimizing 

alternative fumigant applications for ornamental production in Florida. University of Florida 

Extension, Publication ENY-901. http://edis.ifas.ufl.edu/pdffiles/IN/IN81800.pdf [Accessed June 

3, 2013] 

Y ourman, L. 2009. Evaluation of a Request for a Public Interest Finding for the Conditional 

Registration ofDMDS (Dimethyl Disulfide) (DP# 367368), Dec 02, 2009. 

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