### MEMORANDUMUNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D
.C. 20460 

## JUN 24Z0\3

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### SUBJECT: BEAD Chemical Profile (BCP) for Registration Review ofDimethyl Disulfide


### FROM:

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TO: (029088) Leonard Yourman, Plant Pathologist Biological Analysis Branch Jihad Alsadek, Economist 

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# lt.J~-~-.f.ei~**.** Science Information and Analysis Branch Derek Berwald, Economist

## ~(**~** \fl./\( ,· Economic Analysis Branch 

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## v,.**\~** Arnet Jones, Chief

# ~ Biological Analysis BrancH 

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Diann Sims, Chief

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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 ofthis BEAD Chemical Profile (BCP) is to convey usage information and a broad overview ofthe pest management roles ofpesticides that are beginning to undergo registration review. The anticipated audience consists ofthe team ofEPA staffcurrently evaluating the registration status ofdimethyl disulfide and eventually the general public. This document buildsupon the dataprovided by BEAD inthe usage and label use datapackages that are also provided to Registration Review teams. The document is based oninformation and data available to BEAD as ofMay, 2013. Dimethyl disulfide (DMDS) is formulated as a soil fumigant targeting a spectrum ofsoil 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, 2010).
COMMON FORMULATIONS AND APPLICATIONMETHODS 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. Itis 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 ofpests. Tarps must cover areas treated with DMDS. Tarps generally enhance the efficacy ofa fumigant and for DMDS, canhelp 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 inJuly of2010, is used as a pre-plant fumigant in soil to control or suppress nematodes, various soilborne pathogens, nematodes, and weeds in fields in whichberries, 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 ofapplication. However, odor from soils treated with DMDS appears to be ofconcern

2to growers and reduces the incentive to use DMDS on land inproximityto residential areas. Generally, DMDS has shown efficacy infield trials against some pests, and generally, has been shown to provide comparable efficacy to methyl bromide. For example, in Floridavegetable trials to identify methyl bromide alternatives, DMDS with chloropicrin (21 %) provided goodto excellent control ofnematodes andpathogens, and excellent control ofnutsedge (but poor control ofannual grasses, whichrequired an additional herbicide application) (Noling et al., 2012). In Georgia, trials were conducted to assess the efficacy ofa DMDS mixture orcoapplication with chloropicrin and 1,3-dichloropropene against nutsedge intomato and pepper production (Culpepper et al., 2012). The objective ofthe multi-season study is to provide easy application, lowbufferrestrictions, minimal odor, acceptable costs, and efficacy comparable to a standard 50:50 formulation ofmethyl bromide:chloropicrin. The results based ontwo seasons of data showedthat the objectives ofthe study were obtainable. Furthertrials are being conducted, in 2013, to improve pestmanagement 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 (Rosskopfet al., 2012). In Michigan cucurbit field trials with soil infested withthe pathogenPhytophthora capsici DMDS:chloropicrin (79:21) provided yields similar or greaterthan cucurbit soils treated with methyl bromide:chloropicrin (67:33) (Hausbeck et al., 2012)
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. ROLE OF DMDS IN PEST CONTROL In 2009, BEAD evaluated a request for a finding that a conditional registration was in the public interest (Yourman, 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- Dwhose use may be limited due to label restrictions, such as in karst formations in Florida. Currently DMDS is notregistered in California, butifthere is a future registration, DMDS would likely be an important alternative to 1,3-D, whichhas caps on its overall use in agricultural townships. Since the voluntary cancellation ofiodomethane the value ofDMDS as a fumigant may be even more important for growers as a methyl-bromide alternative. However, widespread adoption ofDMDS would likely require addressing its odorproblempossibly through innovative application methods. A registration in California would also likely increase the use ofDMDS.
INFORMATION THAT MAYBE USEFUL FORBEAD'S FUTURE WORK ON DIMETHYL DISULFIDE BEAD has no usage data for DMDS. While results ofexperimental trials have beenpublished, information on commercial use ofDMDS and comparative efficacy would be helpful for any issues that might needto be addressed in registration review. In addition, cost data and geographical use information canbe importantto evaluatingthe benefits ofDMDS
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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-1O.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 ofFloridaExtension, 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 ofFlorida Extension, Publication ENY-901. http://edis.ifas.ufl.edu/pdffiles/IN/IN81800.pdf [Accessed June 3, 2013] Yourman, L. 2009. Evaluation ofa Request for a Public Interest Finding for the Conditional Registration ofDMDS (Dimethyl Disulfide) (DP# 367368), Dec 02, 2009.

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