UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MAR 11 2015 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile (BCP) for Registration Review: Carboxin (090201) and 

Oxycarboxin (090202) 

FROM: Leonard Yourman, Ph.D., Plant Pathologist {t 

Biological Analysis Branch · 

THRU: 

Don Atwood, Ph.D., Entomologist $~~ ///' ?'~ Science Information and Analysis Branch 

Economic 

Michele Ranville, 

Analysis 

Economi

Branch 

st ( 

V 

rrYf /~ ~ 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branc 

Diann Sims, Chief 

Science Information .an Analysis Branch 

Tim

Economic othy Kiely, Analysis 

Chief 

Branch ~ vA-\~ Biological and Economic Anal s Division 3P) 

TO: Dana Friedman, Chemical Review Manager 

RMIB2 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: December 17, 2014 

Page 1 
SUMMARY 

Carboxin and oxycarboxin were first registered in the U.S. in 1968 and 1971, respectively. Both 

fungicides are members of the oxathiin-carboximide class of systemic fungicides. They are 

classified by the Fungicide Resistance Action Committee as Group 7 succinate dehydrogenase 

inhibitors (SDHI). Carboxin and oxycarboxin were the first generation of SDHI fungicides, 

followed several years later by broader spectrum SDHI fungicides such as boscalid and 

fluopyram, among others (A venot and Michailides, 201 0). 

Agricultural use is limited to carboxin as a seed treatment. The major agricultural use sites for 

carboxin are seed treatments of wheat (spring and winter), peanuts, soybean, and cotton. 

According to available proprietary information, the major usage of carboxin in terms of both 

total pounds applied and total acres treated is on winter wheat seed. 

Non-agricultural use sites for both carboxin and oxycarboxin include ornamentals. However, 

oxycarboxin use (targeting rust pathogens) is limited to foliar application to ornamentals in 

enclosed commercial structures such as greenhouses, shadehouses, and interiorscapes. 

INTRODUCTION 

The Biological and Economic Analysis Division (BEAD) Chemical Profile (BCP) provides an 

overview of the pest management roles and quantitative usage information for carboxin and 

oxycarboxin. The BCP includes summaries of previous BEAD products and available public 

and/or private use and usage data for carboxin and oxycarboxin to describe the role of this 

chemical in pest management. Additional information on use is available in the Carboxin Label 

Data Report and the Oxycarboxin Label Data Report provided in the public docket for this 

chemical. Information provided in this BEAD Chemical Profile (BCP) may be used by 

stakeholders (e.g., users and registrants), OPP risk assessors and risk managers, and the general 

public during the Registration Review process of this pesticide. 

AGRICULTURAL USE SITES 

Carboxin is registered as a seed treatment of barley, beans, canolalrape, corn (field, pop, and 

sweet), cotton, grasses grown for seed, mustard, oats, onion, peas, rice, rye, safflower, sorghum, 

soybeans, triticale, and wheat. 

Oxycarboxin is not registered for agricultural use. 

NON-AGRICULTURAL USE SITES 

Ornamentals are the only non-agricultural use sites for which carboxin dip application is labeled 

in some locations. Oxycarboxin is only registered for foliar application on ornamentals grown in 

enclosed commercial structures such as greenhouses, shadehouses, and interiorscapes. 

Page 2 
FORMULATIONS AND APPLICATION METHODS 

Carboxin is formulated for seed or dip treatment as a flowable concentrate, emulsifiable 

concentrate, dust, and ready-to-use product. Carboxin is applied as either a seed or dip treatment 

both by commercial seed treaters and on-farm applicators. Depending upon the formulation, 

application equipment may include cup, dip tank, mist-type seed treater, slurry-type seed treater, 

hopper box, and planter/seed box. 

Oxycarboxin is formulated as a wettable powder and may only be applied as foliar application by 

commercial applicators utilizing hand held equipment. 

HISTORY OF CARBOXIN/OXYCARBOXIN AND BEAD PRODUCTS 

Carboxin was first registered for use in the U.S. in 1968 (EPA 2004). Oxycarboxin was 

registered for use in 1971. A Reregistration Eligibility Decision (RED) was issued for carboxin 

in 2004. An addendum to the RED for oxycarboxin was issued in 2005. The carboxin RED 

required additional label language to avoid environmental hazards and occupational exposure. 

A search of BEAD's Official Records and the OPP Section 18 database did not find any Section 

18 requests or benefits assessments for carboxin or oxycarboxin in the last 10 years. Emergency 

exemptions may indicate that there is a need for a particular chemical that is not registered for 

use on a particular site. An emergency exemption request may yield information about a 

particular chemical's importance or value that is not found in other EPA records.· However, a 

lack of Section 18 assessments by BEAD does not specifically indicate the relative importance of 

the chemical. 

CARBOXIN USAGE 

Agricultural Usage 

Usage of carboxin in terms of number of acres treated and totallbs applied was minor from 

2006-2008 (Figure 1). In 2009, carboxin usage showed an apparent increase which remained 

relatively constant through 2011. The increase during this time frame is likely related to 

increased use on soybeans and new usage on wheat. From 2011 to 2012, there was a reduction 

in carboxin usage resulting from decreased usage on both soybeans and winter wheat. Figure 1 

shows a sharp increased usage from 2008 to 2009 and a decreased usage from 2011 to 2012. 

This may be due at least in part to its scale. The crops listed in Table 1 are planted on a total of 

well over one hundred million acres per year (fluctuating by millions of acres per year). 

Considering the fluctuation of plantings of these major crops and the low range of percent crop 

treated (e.g., soybean: <1 to <2.5 PCT) (Table 2), the change of usage on seed that might be 

planted on approximately 1 million acres out of more than 100 million acres for these crops 

Page 3 
would appear in line with the PCT ranges and may explain the large increase and decrease in 

usage between 2008 and 2012. 

-o "' Ql Ql 

.... ._ IV 

... Ql <t ... 1-

1400000 

0 

Historical Carboxin Usage 

........ ,_.•----· 

2006 2007 2008 2009 

Year 

2010 2011 

Sum ofTotal Area Treated - •- Sum of Pounds AI 

Figure 1. National Carboxin Agricultural Usage from 2006 to 2012. 

Source: Proprietary Data, 2006-2012 

60000 

0 

2012 

A review oftotal carboxin usage from 2009-2012 indicates that the primary use site is wheat, 

accounting for approximately 56% of both totallbs applied and 66% of total acres treated (Table 

1 ). Carboxin average application rates range from 0.010 to 0.89 lbs a. i./acre for the major use 

sites in the United States with lowest application rate on cotton and the highest application rate 

on peanuts. However, while wheat has the highest percentage of lbs applied and total acres 

treated, the crop with the highest percent crop treated is peanuts with an average of 5% crop 

treated and a maximum of 10% crop treated (Table 2). 

Page4 
Table 1. Crops with Highest Use ofCarboxin (2009-2012). 

Crop Lbs A.I. %of Total Total Acr es % ofTotal 

Avg. A.l. Rate Applied Carboxin Treated* Carboxin 

Lbs Applied Treated Acres (lbs a .i./acres) 

Winter Wheat 78,424 46 2,200,158 54 0.036 

Soybean 53,323 31 1,089,933 27 0.049 

Peanuts 21 ,060 12 236,635 6 0.089 

Spring Wheat 17,285 10 475,488 12 0.036 

Cotton 514 0 52,584 1 0.010 

*Total Acres Treated sums all acres treated for a crop, mcludmg those acres that rece1ve mult1ple treatments. 

Source: Proprietary Data, 2009-2012 

T a bl e 2 . P ercent C T rop d . hC b . reate Wit ar oxm. 

Crop Percent Crop Treated 

Average Maximum 

Winter Wheat <2.5 <2.5 

Soybean <1 <2.5 

Peanuts 5 10 

Spring Wheat <2.5 <2.5 

Cotton <1 <2.5 

Source: BEAD 2014 SLUA 

Table 3 indicates states with highest usage of carboxin in terms of lbs a.i. applied and acres 

treated. Louisiana and Georgia are the states with highest car box in usage in terms of total lbs of 

carboxin applied ( 13%). The six states in Table 3 with most lbs applied represent 60% of total 

lbs applied and are the only states which exceed 5% of total carboxin lbs applied. Washington, 

Louisiana, and Texas are the states with the highest percent of total acres treated at 11%. These 

states with most usage account for 57% of total acres treated with carboxin with no other state 

exceeding 6% of acres treated. Highest application rate, 0.062 lbs a.i./acre, is used in Georgia 

and lowest application rate is in Texas, 0.035 lbs a.i./acre. 

Table 3. States with Highest Use of Carboxin (2009-20 12). 

State Total Lbs %of Total Total %of Total 

Applied Carboxin Acres Acres Treated A vg. A.I. Rate 

Lbs Applied Treated* witb (lbs a.i./acres) 

Carboxin* 

Louisiana 22,598 13 438,500 11 0.052 

Georgia 22,092 13 372,200 9 0.062 

Washington 17,033 10 453,600 11 0.038 

Texas 15,068 9 427,800 11 0.035 

Mississippi 14,3 19 8 294,100 7 0.051 

Oklahoma 11,525 7 311 ,600 8 0.037 

*Total Acres Treated sums all acres treated, mcludmg those acres that rece1ve multtple treatments. 

Source: Proprietary Data, 2009-2012 

Page 5 
Geographic Distribution of Carboxin Use 

Carboxin has wide usage in the United States (Figure 2) with the exception of New England and 

Southwestern United States. States with highest pounds per 1,000 crop acres grown include 

Washington, Louisiana, Georgia, and Mississippi and primarily reflect use on winter wheat, 

soybeans, peanuts, and soybeans, respectively. 

Pounds Active Ingredient 

per 1,000 Crop Acres Grown 

0 NoData 

D <o.o3 

CJ o.o3 - 0.1 

O o.1-0.3 

.0.3-0.6 

->0.6 

Figure 2. Annual average agricultural use intensity of carboxin (2008-20 12). 

Non-Agricultural Usage 

No estimate of non-agricultural usage of carboxin on ornamentals is available from proprietary 

data sources. Special Local Need 24C labels are in effect for carboxin-containing products in 

Oregon for treating grass seed for export only. 

Page 6 
OXYCARBOXIN USAGE 

Agricultural Usage 

There is no agricultural usage for oxycarboxin. 

Non-Agricultural Usage 

Non-agricultural usage data for oxycarboxin are not available. 

BIOLOGICAL ASPECTS RELEVANT TO CARBOXIN AND OXYCARBOXIN 

Carboxin and oxycarboxin are classified by the Fungicide Resistance Action Committee as 

Group 7 succinate dehydrogenase inhibitors (SDHI). Carboxin and oxycarboxin were the first 

generation of SDHI fungicides, followed several years later by broader spectrum SDHI 

fungicides such as boscalid and fluopyram among others (Avenot and Michailides, 2010). SDHI 

fungicides interrupt respiration by blocking electron transport in the mitochondria. The systemic 

characteristic of carboxin and oxycarboxin make them valuable where required for controlling 

seed-borne and seedling diseases, primarily basidiomycete pathogens, such as rusts, smuts, and 

bunts (Ulrich and Mathre, 1972). Oxycarboxin is labeled for use to manage rust diseases on 

ornamental plants grown in enclosed structures. 

ROLE OF CARBOXIN AND OXYCARBOXIN IN PEST MANAGEMENT 

The first generation SDHI fungicide carboxin is generally effective as a seed treatment against 

seed and seedling diseases caused by basidiomycete fungi, such as loose smut, common bunt of 

wheat, covered smut, scab seedling blight, flag smut, as well as some seedling diseases such as 

Rhizoctonia root rots of soybean (e.g., McKay et al., 2011; Schultz and French, 2011 ). 

Carboxin 

Until the registration of carboxin as a seed treatment winter wheat was susceptible to new races 

of smut fungi (Crop Profiles for Winter Wheat in Oregon, 1999). Eastern Oregon winter wheat 

seed was nearly all treated with fungicide. Until 1995, the seed treatment of choice was carboxin 

alone or mixed with other fungicides and/or insecticides. Since the mid-1990s, other seed 

treatment fungicides have been available, some of which have been more effective than carboxin 

(Crop Profiles for Winter Wheat in Oregon, 1999). 

For wheat grain production, in determining if there is a value from treating seed the grower must 

balance the cost of seed treatment with the return (Dewolf, 2013; Byamukama and Fanning, 

20 14; Paul, 2011 ). Where there is no prior history of seed-borne diseases (such as smuts and 

bunts) in the field, the value of a fungicide seed treatment may be minimal, especially in good 

planting weather. Seed treatment for loose smut where it has been observed requires a systemic 

fungicide, including carboxin, tebuconazole, and difenoconazole. However, extension specialists 

Page 7 
recommend that wheat kept for seed the next season be treated with fungicide(s). Fungicide 

treatments may help seed with low germination rates (less than 90%) improve stand 

establishment (DeWolf, 2013). Where wet soils are encountered during planting fungicide seed 

treatments have been recommended (e.g., Bosley, 2009; Paul, 20011; Byamukama and Fanning, 

2014). 

For wheat seed used for seed production systemic treatments such as carboxin and others, 

fungicides are recommended (Dewold, 2013) to reduce the likelihood of smuts and bunts being 

introduced into stocks. Because of the value of seed stock, treatment is usually considered 

economically justifiable. 

Damping off and seedling rots, including Rhizoctonia, can be problem seedling diseases of 

soybean. Carboxin is one of several seed treatments available (e.g., Giesler and Ziems, 2008; 

Osborne and Ruden, 2011 ). As with the case in wheat, soybean seed treatments are indicated 

when conditions indicate that seedling diseases may be a problem either due to past experience 

in the field or because of impending weather causing cool wet soils at planting. Seed treatments 

are also advised when planting seeds of marginal quality (e.g., Koenning et al., 2000). It was 

estimated that 60-70% of the 2014 soybean seed planted was treated with fungicides, compared 

with 30% in 2008 and 8% in 1996 (USB, 2014). 

All commercial cotton seed is treated with fungicides. Typically systemic fungicides such as 

carboxin are combined with protectant fungicides such as captan for greater seed protection (e.g., 

Koenning, undated). Common cotton seedling diseases that fungicide seed treatments target are 

Pythium, Rhizoctonia, and Fusarium rots (Wrather and Sweets, 2009; Padgett et al., 2002). 

All commercial peanut seed is treated with fungicides. Several multi-a.i. products are used as 

peanut seed treatment, including those with carboxin. Treated seed generally provide improved 

germination, seedling rot inhibition, and can help prevent field-contamination of 

Cylindrocladium parasiticum (e.g., Spears et al, 2002). Carboxin may be used as a seed 

treatment and is typically mixed with other fungicides (OSU, 2012). Other fungicides may be 

applied in-furrow at planting. 

Three 24C SLN labels are currently in effect for carboxin to treat grass seed for export to control 

seedling diseases such as damping-off, Pythium damping-off, Rhizoctonia rots (WSU, 2014). 

According to the Oregon Seed Association (Perkowski, 2013): "The value and volume of 

ryegrass seed exports surged in 2011 , stayed strong in 2012, and saw a healthy uptick during the 

first quarter of 2013 ... Higher sales in early 2013 likely represented the tail end of the upswing in 

exports ... The dimming prospects for exports are largely due to the market outlook in Europe, a 

major buyer of perennial ryegrass seed for turf. Unseasonably low temperatures and adverse 

weather in Europe have hampered demand for perennial ryegrass seed ... " 

Page 8 
Oxycarboxin 

Several fungicides are available for managing rust diseases on ornamentals in enclosed structures 

such as greenhouses (UMass, undated). These include myclobutanil, fludioxonil, fluoxastrobin, 

flutolanil, chlorothalonil, and azoxystrobin. BEAD did not extensively evaluate the relative 

efficacy of registered a.i.s, although one early efficacy study found that oxycarboxin generally 

was effective (along with myclobutanil) for managing carnation rust in California greenhouses 

(Ferrin and Rohde, 1991 ). 

DATA NEEDS 

The Agency currently does not have important information on carboxin and oxycarboxin. 

Obtaining the following information for all registered non-agricultural sites may improve future 

assessments conducted by the Agency related to the use and importance of carboxin and 

oxycarboxin: 

Usage 

• Total pounds active ingredient applied 

• Percent crop/site treated . 

• Application rates: typical and maximum 

• Frequency of application 

• Application Intervals 

• Methods of application 

• Target or niche pests 

• Efficacy information/product performance 

REFERENCES 

Avenot, H. F. and Michailides, T. J. 2010. Progress in understanding molecular mechanisms and 

evolution of resistance to succinate hehydrogenase inhibiting (SDHI) fungicides in 

phytopathogenic fungi. Crop Protection 29:643-651. 

BEAD. 2014. Screening Level Usage Analysis (SLUA) for Carboxin. 

Bosley, D. B. 2009. Wet year may mean fungus in wheat harvest, seed crops. Fort Morgan 

(Colorado) Times, Aug. 27, 2009. http://www.fortmorgantimes.com/fort-morganagriculture/ci 13217356 

Byamukama, E. and Fanning, B. 2014. South Dakota wheat: Planning fungicide seed treatments. 

Agfax.com. http :I I agfax.com/20 14/08/22/ south-dakota-wheat -planning-fungicide-seedtreatments/ 

Page 9 
Crop Profiles for Winter Wheat in Oregon. 1999. 

http://www .ipmcenters.org/ cropprofiles/ docs/ orwheat. pdf 

DeWolf, E. 2013. Fungicide seed treatments for wheat. No-Till Farmer. Oct. 7, 2013. 

http://www.no-tillfarmer.com/pages/News---Fungicide-Seed-Treatments-For-Wheat.php 

EPA. 2004. Carboxin Fact Sheet. 

http://www .epa. gov I oppsrrd 1 /REDs/factsheets/00 l2fact carboxin. pdf 

Ferrin, D. M. and Rohde, R. G. 1991. Tests compare fungicides for control of rust on greenhouse carnations. California Agriculture 45:16-17. 

http://ucanr.edu/repositoryfiles/ca4504p16-69551.pdf 

Giesler, L. J. and Ziems, A. D. 2008. Seed treatment fungicides for soybeans. University of 

Nebraska Extension. http://ianrpubs. unl.edu/pages/publicationD. j sp?publicationld= 1 007 

Koenning, S., Ferguson, J. and Dunphy, E. J. 2000. Soybean seed and seedling diseases. North 

Carolina State University Extension. 

http://www.ces.ncsu.edu/depts/pp/notes/Soybean/soy002/soy002.htm 

Koenning, S. Undated. Cotton seedling diseases. North Carolina State University Extension. 

http://www .ces. ncsu.edu/ depts/pp/notes/Cotton/ cdin 1 I cdin l .htm 

McKay, A H., Hagerty, G. C., Follas, G. B., Moore, M. S., Christie, M.S., and Beresford, R. M. 

2011. Succinate dehydrogenase inhibitor (SDHI) fungicide resistance prevention strategy. New 

Zealand Plant Protection 64:119-124. http://nzpps.org/journal/64/nzpp 641190.pdf 

Osborne, L. and Ruden, K. 2011. Seed treatment fungicide options for soybeans in South 

Dakota. South Dakota State University Extension Publ. FS966. 

http:/ /pu bstorage. sdstate.edu/ AgBio Publications/articles/FS966.pdf 

OSU. 2012. Peanut disease control guidelines. Oklahoma State University Extension. 

http:/ /entoplp.okstate.edu/profiles/jd/20 12%20Peanut%20Disease%20Control.pdf 

Padgett, B., Colyer, P., Burris, E. and Whitam, K. 2002. Hopper box applied fungicides for 

management of cotton seedling diseases. 

http://www.lsuagcenter.com/en/communications/publications/agmag/Archive/2002/Winter/Hopp 

er+ Box+ Applied+ Fungicides+for+Management+of+Cotton+Seedling+Diseases.htm 

Paul, P. 2011. Winter wheat seed needs fungicide seed treatment. Prairie Star, Oct. 8, 2011. 

http://www.theprairiestar.com/news/crop/winter-wheat-seed-needs-fungicide-seedtreatment/article f13a3096-fl b6-11e0-b175-00lcc4c002eO.html 

Perkowski, M. 2013. Experts say ryegrass seed exports have likely peaked. Oregon Seed 

Association. http://www .. oregonseed.org/experts-say-ryegrass-seed-exports-have-likely-peaked/ 

Page 10 
Proprietary Data. 2006-2012. 

Proprietary Data. 2008-2012 

Proprietary Data. 2012 

Schultz, D. and French, R. D. 2011. Fungicide seed treatment decisions for use on winter wheat. 

Texas A&M University Extension. 

http://amarillo.tamu.edu/files/20 1 0111 /WheatFungSeedTrtPLPA WhtSdO 11-1.pdf 

Spears, J. F., Jordan, D. L., and Bailey, J. E. 2002. Peanut seed production: A guide for 

producers of Virginia-type peanut seed. North Carolina State University Extension Publ. AG622. http://www.peanut.ncsu.edu/PDFFiles/004968/Peanut Seed Production Guide.pdf 

Ulrich, J. T. and Mathre, D. E. 1972. Mode of action of oxathiin systemic fungicides. Journal of 

Bacteriology, 110:628-632. 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC24 7 458/pdf/jbacter00361-0 188.pdf 

UMass. Undated. Rusts- Fungicides. University of Massachusetts Extension. (accessed 

12/2/2 0 14). http:/ I greenhousediseaseguide. urn ass. edu/rusts2 

USB. 2014. Six things farmers should now about seed treatments. United Soybean Board, Feb. 

20, 2014. http:/ /unitedsoybean.org/article/six -things-farmers-should-know-about-seedtreatments/ 

Wrather, A. and Sweets, L. 2009. Cotton seedling diseases: Answers to frequently asked 

questions. Univerity of Missouri Extension Publ. MP734. 

http://extension.missouri.edu/explorepdf/miscpubs/mp0734.pdf 

WSU. 2014. Washington and Oregon SLNs. (accessed 12/2/2014). 

http://picolsln.wsu.edu/slnDisplay.aspx?state=OR 

Page 11 
APPENDIX A 

The map included herein is primarily for the use of the risk assessors in the Environmental Fate 

and Effects Division. The map provides a very broad geographical view of the average annual 

amount (in pounds) of the active ingredient applied per 1,000 acres of crop acres grown. These 

data are included in the maps because risk assessors are interested in the amount of a pesticide 

used across agricultural land. The calculated values presented in the map are not equivalent to 

an application rate (lb ai/ A). 

The data used to make these maps have several limitations. Any interpretation of the maps 

should consider the underlying data and the associated limitations carefully. 

The numerator (annual average pounds applied) is based on private market surveys of pesticide 

use in agriculture averaged over the last five years (Proprietary Data, 2008-2012). These surveys 

cover about 60 crops and are targeted in states that produce the majority of the crop. Although 

the surveys capt~re most of the use of a particular active ingredient in agriculture, there are 

several limitations to these surveys. 

• States with minor production of a surveyed crop are not sampled 

• Not all types of pesticides are surveyed in every crop in every year 

• Many specialty crops with very small acreages are not included in the survey 

The result of these limitations is that states that show no usage may actually have a small amount 

of the active ingredient being used. In some cases the displayed use intensity may be distorted 

because the surveyed crops and the reported pesticide usage may not accurately represent the 

actual pesticide usage on the crops produced in the state. 

The denominator (1 ,000 crop acres grown) was also obtained from the same private market 

survey database. The "Crop Acres Grown" variable represents the total acres grown in a given 

state of all of the surveyed crops. This value is independent of pesticide usage and pesticide 

registration. It is important to note that the surveyed crops (about 60) are sampled from states 

that are major producers of each crop. Therefore, there are cases where the actual crop acreage in 

a state is higher than that reported by crop acres grown in the survey because either that state 

and/or crop was not included in the survey. 

The reader should pay particular attention to the figure legends and realize that a map prepared 

for a particular chemical is not directly comparable to a map prepared for a different chemical as 

the legend bins will likely be different. 

Page 12