UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

APR 0 9 1tl14 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

BEAD Chemical Profile (BCP) for Registration Review: Mesotrione (122990) 

Sunil Ratnayake, Ph.D., Biologist ~MD ~ /1 n 

Biologica!AnalysisBranch L - v·· ~ ~ 

Don Atwood, PhD., Entomologist JJ'" ~ ?J7 vb 

Science Information and Analysis Branch 

Stephen Smearman, Economist j. 1 . J _ .. __ 

Biological 

Economic Analysis 

and Economic 

Branch 

Analysis 

~ 

Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Diann Sims, Chief 

16akL 

Science Information and Analysis Branch 

Timothy Kiely, Chief ~ , A A I , f 

Economic Analysis Branch -._J vv'--~0 Biological and Economic Analysis · ision (7503P) 

TO: Jolene Trujillo, Chemical Review Manager 

Pesticide Re-evaluation Division (7508P) 

Peer Review Panel date: March 5, 2014 

Page 1 
SUMMARY 

Mesotrione was first registered in the U.S. in 2001 and it belongs to the triketone family of 

herbicides. It is a selective herbicide registered for control ofbroadleafweeds in many 

agricultural and non-agricultural use sites. Mesotrione can be applied as pre-emergence and 

post-emergence treatments in agricultural and non-agricultural use sites. The mechanism of 

action of mesotrione is the inhibition of 4-hydroxypenyl-pyruvate dioxygenase ( 4-HPPD), an 

enzyme found in plant species and the interference of this enzyme leads to the destruction of 

chlorophyll and killing the susceptible plants. Mesotrione is an important tool used in resistance 

management programs. It provides an effective control of several key weed species with 

resistance to glyphosate, triazines, protoporphyrinogen oxidase (PPO) and acetolactate synthase 

(ALS) inhibiting herbicides. 

The major agricultural use sites include; blueberries, caneberries, cranberries, rhubarb, pop com, 

field com, sweet com, okra, asparagus, millet, oats, sugarcane, sorghum, and soybeans. The 

registered non-agricultural use sites include; lawns, ornamental turf, ornamental flowering 

plants, and recreational areas. According to the publicly available usage information, the highest 

usage, in terms of totallbs applied and total acres treated of this herbicide was on com. 

INTRODUCTION 

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

overview of the pest management roles and quantitative usage information for mesotrione. The 

BCP includes summaries of previous BEAD products and available public and/or private use and 

usage data for mesotrione to describe the role of this chemical in pest management. Additional 

information on use is available in the Mesotrione PRD 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 OPP risk managers, 

and the general public during the Registration Review process of this pesticide. 

AGRICULTURAL USE SITES 

Mesotrione is registered for use on blueberries, caneberries, cranberries, rhubarb, popcorn, field 

com, grass grown for seed, sod, sweet corn, okra, asparagus, millet (pearl and proso ), oats, 

sorghum (grain and sweet), sugarcane, flax, and soybeans. 

NON-AGRICULTURAL USE SITES 

Non-agricultural use sites which are labeled for Mesotrione application include lawns, 

ornamental turf (i.e. commercial lawn, golf courses, cemeteries, and athletic fields), ornamental 

flowering plants ( cuphea), and recreational areas. 

Page2 
FORMULATIONS AND APPLICATION METHODS 

Mesotrione has seven formulations. These are granular, water dispersible granules, emulsifiable 

concentrate, soluble concentrate, solution-ready to use, pressurized liquid, and soluble 

concentrate/solid. 

Mesotrione is applied pre- and post-emergence through ground or aerial application equipment 

HISTORY OF MESOTRIONE AND BEAD PRODUCTS 

Mesotrione was first registered for use in the U.S. in 2001 by Syngenta Crop Protection Inc. 

under the Callisto® product label. In the past five years, BEAD conducted two justification 

reviews for the extension of the exclusive use period for mesotrione (USEPA, 2010 and 2011). 

Syngenta Crop Protection Inc. submitted a petition to the Agency, in January 2009 requesting the 

exclusive data use period be extended for three additional years for data submitted in support of the 

mesotrione registration. Syn:genta provided infonnation for 14 crops and BEAD detennined that 7 

crops met the criteria which was that mesotrione was needed because there were insufficient 

alternatives available and for managing pest resistance. Following BEAD's review in March 2010, 

the Agency granted extension of exclusive data use period for 2 additional years and the new 

expiration date of this extension period was June 2013. A total of nine minor crops were needed to 

meet the criteria for granting maximum duration of 3 years for the extension of exclusive data use 

period. In April2011, Syngenta submitted infonnation on four additional crops; blackberry, 

raspberry, okra, and lingonberry for consideration. BEAD reviewed submitted infonnation and 

detennined that of these four minor crops, okra and blackberry meet the criteria for extension of 

exclusive data use period because mesotrione was needed in managing pest resistance to other 

alternatives for these two crops. 

There have been no Emergency Exemption reviews conducted by BEAD for mesotrione in the 

last 5 years. Furthermore, there are no active Emergency Exemptions for mesotrione. 

MESOTRIONE USAGE 

Agricultural Usage 

Usage of mesotrione and number of acres treated both showed a steady increase from registration 

in 2001 through 2007 (Figure 1). After 2007, mesotrione usage (both in terms of pounds applied 

and total area treated) exhibited a slight decline but had reached the previous usage level by 

2011. Usage further increased in 2012 and appears to indicate a trend of increased mesotrione 

usage. The increase in mesotrione usage on com acreage may be due to its use in resistance 

management (especially glyphosate resistance management). 

Page3 
3.000.000 . r--·---·····--·-----·-· 

l 

I 

I I 

i 

i 

I 

I 

---·------···- .. 

j -PoundsAI 

o L. __,...---. -- ---.- ----~---~----,--....,.--____, 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 

Source: Proprietary Data, 2008-2012 

Fi 2. National Mesotrione Us e (Acres Treated) from 2001 to 2012. 

30,000,000 .---------------·-----------

-Total Area Treated . 

(acres) 

--- ····--- --·---------.,.-----

L 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 

-----~-~~~~---- Souree: Proprietary Data, 2008-2012 

A review of total mesotrione usage data for the last 5 years indicates that the primary use site is 

com, accounting for approximately 98% of both totallbs applied and total acres treated (Table 

1). Table 2 indicates that of the crops with highest mesotrione use, field com represents the 

highest percent crop treated in terms of acres grown and acres treated at 20.2%. 

Page4 
Table 1. Crop(s with the Hi~est Use ofMesotrione (2008-2012) 

Crop LbsAI o/o of Total Total Acres % of Total Acres 

(l,OOO's) Mesotrione Lbs Treated Treated with 

Applied (1000's)* Mesotrione 

Field Com 9,910 97.6 90,449 97.7 

*Total Acres Treated sums all acres treated for a crop, mcluding those acres that receive multiple treatments. 

Source: Proprietary Data, 2008-2012 

Table 2. Percent Crop Treated with Mesotrione for specific crops based on total acres 

KA u" .. and total acres treated (2008-2012) 

Crop Crop Acres Grown Total Acres Treated Percent Crop Treated 

(l,OOO's) (l,OOO's)* 

Field Com 447,630 90,449 20.2 

Sorghum 31,350 1,633 5.2 

Sweet com 2,745 472 17.2 

*Total Acres Treated smns all acres treated for a crop, mcludmg those acres that receave multiple treatments. 

Source: Proprietary Data, 2008-2012 

Table 3 indicates states with highest usage of mesotrione in terms of lbs ai. applied and acres 

treated. Iowa, Illinois and Nebraska are the only states where percent lbs a.i. applied and percent 

acres treated exceed 1 0% of national usage. 

Table 3. States with Highest Use ofMesotrione (2008-2012) 

State o/o of Total State % of Total Acres 

Mesotrione Lbs Treated with 

Applied Mesotrione* 

lllinois 15.8 Iowa 16.7 

Iowa 13.4 lllinois 15.7 

Nebraska 13.1 Nebraska 12.7 

Indiana 8.3 Minnesota 8.8 

Kansas 7.8 Kansas 7.7 

Wisconsin 7.1 Indiana 7.2 

Minnesota 6.5 Wisconsin 6.1 

*Total Acres Treated smns all acres treated, mcludmg those acres that receave multiple treatments. 

Source: Proprietary Data, 2008-2012 

Awlication Rates and Methods 

The average mesotrione application rate is highest for sweet com at 0.128 lbs a.i.lacre, as shown 

in Table 4. However, most U.S. treated acreage, field com, is treated at a slightly lower 

application rate of 0.110 lbs a. i./acre. 

PageS 
T a e bl 4 M • esotrione u seon T C op_ rops: A verage A.I . Ra te, 2008 -2012 

Average Total Lbs Average Total Acres Avg. A.I. Rate Crop Treated (1000's) (l,OOO's)* (lbs a.Uaeres) 

Com 1,982 18,090 0.110 

Sorghum 37 327 0.114 

Sweet com 12 94 0.128 

*Total Acres Treated sums all acres treated for a crop, mcluding those acres that rec:etve multiple treatments. 

Source: Proprietary Data, 2008-2012 

Table 5 provides average mesotrione application rate by state. Highest application rate, 0.128 

lbs a i./acre, is used in Indiana and Wisconsin. However, the rate in Indiana is entirely based on 

usage on field com while the rate in Wisconsin represents the combined usage rates for field com 

(0.127lbs ai.lacre) and sweet com (0.152lbs ai.lacre). Lowest application rate is for field com 

in Iowa, 0.088 lbs aiJacre. 

T a e bl 5 M • esotrione U sem . T op Sta tes: A vera e A.I . Rat te, 2008 -2012 

State Average Total Lbs Average Total Avg. A.I. Rate Applied Acres Treated 

(l,OOO's) (l,OOO's)* (lbs a.Uaeres) 

Illinois 320 2,908 0.110 

Iowa 272 3,100 0.088 

Nebraska 266 2,359 0.113 

Indiana 169 1,324 0.128 

Kansas 158 1,428 0.110 

Wisconsin 144 1,130 0.128 

Minnesota 131 1,629 0.081 

*Total Acres Treated sums all acres treated, mcluding those acres that recetve multiple treatments. 

Source: Proprietary Data, 2008-2012 

According to proprietary data, broadcast application accounts for 98% of mesotrione lbs applied 

and acres treated. Timing of mesotrione application is evenly split between pre-plant/emergence 

and post emergence. Mesotrione can be applied twice a year at the maximum label application 

rate of8 fl oz/acre. In addition, custom application accounts for 39.6% of acres treated, fanner 

application 59.8% of acres treated, and aerial application accounts for less than 1% of acres 

treated with mesotrione. 

Page6 
Geographic Distribution of Mesotrione Use 

Mesotrione use is reported in the m~ority of states with varying level ofuse intensity (Figme 3.) 

Use in the western U.S. is limited to Oregon and Washington and reflects low use intensity. 

Regardless of state or usage intensity, usage on this map primarily reflects mesotrione 

application in field com production. Only in Oregon is mesotrione use solely attributed to sweet 

com production. Differences in usage intensity for mesotrione in the central and eastern United 

States is largely the result of differing levels of weed pressures and target weed resistance by 

state. For more information about this map, see Appendix A. 

Figure 3. Annual average agricultural use intensity of Mesotrione (2008-2012). 

Pounds Active lngreclent 

per 1.000 Crop Acres Grown 

c:JNoDoll 

s;~;.; l < 22 

lmlllll22. 82 

' 6.3-10.0 

-10.1-18.0 

-~16.0 

Non-Agricultural Usage 

Data is not available for mesotrione use in non-agricultural sites. 

Page7 
BIOLOGICAL ASPECTS RELEVANT TO MESOTRIONE 

According to the Weed Science Society of America (WSSA) classification ofherbicides, 

mesotrione belongs to the group oftriketone herbicides (Group 27) (WSSA, Undated). 

Mesotrione is a selective and systemic herbicide registered for control of broadleaf weed species 

in many agricultural and non-agricultural use sites. This herbicide can be applied as preemergence and post-emergence treatments and it provides a wider application window for 

control of annual broadleaf weeds. The mechanism of action of mesotrione is the inhibition of 4-

hydroxypenyl-pyruvate deoxygenase ( 4-HPPD), an enzyme found in plant species (WSSA, 

Undated). Inhibition of this enzyme leads to the destruction of chlorophyll in leaves resulting the 

death of susceptible plants (EPA Fact Sheet, 2001). Weed species that can be controlled by 

applications of mesotrione, include common cocklebur (Xanthium strumarium ), velvetleaf 

(Abutilon theophrasti), common lambsquarters (Chenopodium album), species ofsmartweed 

(Polygonum spp.) and giant ragweed (Ambrosia trifida) (Herbicide Handbook, 2007). When 

mesotrione is applied as pre-emergence treatment, it is absorbed through the roots and dry soil 

conditions following the application may reduce the pre-emergence activity. Furthermore, 

application of atrazine and mesotrione as a mixture has shown a synergistic effects on controlling 

certain broadleafweeds such as wild radish (Raphanus raphanistrum)(Michael et al., 2012) and 

Canada thistle (Cirsium arvense) (Gregory et al., 2004). 

If mesotrione is applied as a post-emergence treatment it is absorbed through the weed foliage. 

Only one post-emergence application of mesotrione can be made if mesotrione is applied as a 

pre-emergence treatment and according to the product label, not more than 2 application of this 

herbicide can be made per season. On corn, the recommended maximum application rate per 

year is 0.24lb ail A (Callisto•, Product Label). 

ROLE OF MESOTRIONE IN PEST MANAGEMENT 

Mesotrione is registered for the control of annual broadleaf weed species in many agricultural 

and non-agricultural use sites. It can be applied as pre-emergence and post-emergence 

treatments and this herbicide provides a wider application window for the control of annual 

broadleaf weed species. Mesotrione is not effective on most grass weed species and preemergence or post-emergence grass herbicides can be tank mixed with mesotrione to provide a 

broad spectrum of weed control including the control of grass weeds. Also, mesotrione can be 

used in combination with bum-down herbicides to provide an additional bum-down effect and a 

residual weed control in some crops such as field com, seed corn, yellow popcorn, and sweet 

com. Mesotrione is an important tool that can be used in resistance management programs to 

provide an effective control of several key weed species resistant to glyphosate, triazines, and 

acetolactate synthase (ALS) inhibiting herbicides (Rechards et al., 2002). According to the 

publicly available information, biotypes of only two weed species: Palmer amaranth, 

(Amaranthus palmerz) and Common waterhemp (Amaranthus tuberculatus (syn. Rudis) have 

developed resistance to the mechanism of action ofmesotrione (Weedscience.org, Undated). 

The usage information of mesotrione on minor crops is available only on asparagus, blueberries, 

and cane berries. An average of 5% total acres of asparagus and cane berries are treated with 

PageS 
mesotrione. Similarly, only I 0% of blueberry acreage is treated with mesotrione. The low use 

of mesotrione on these minor crops suggests that mesotrione is not critical for production of 

these crops. However, it cannot be ruled out that mesotrione use on these minor crops may 

represent use for unique niche pests and/or crop conditions in some production areas. 

DATA NEEDS 

The Agency currently does not have important information on mesotrione. Obtaining the 

following information for the following registered agricultural sites: okra, oats, and flax which 

may improve future assessments conducted by the Agency related to the use and importance of 

mesotrione. 

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 

Page9 
REFERENCES 

BEAD 2013. Mesotrione ((122990) Screening Level Usage Analysis. Biological and Economical 

Analysis Division. Office of Pesticide Programs, U.S. Environmental Protection Agency. 

Callisto•, Product Label. 2012. Syngenta. Syngenta Crop Production, LLC. Greensboro, North 

Carolina, NC 27419-8300. Available at: http://www.cdms.net/LDatlld56N005.odf. 

Accessed date, Jan. 6 2014. 

Gregory, R. A., Hall, G. J., Wilson H. P., and N. Cullen. 2005. Mesotrione Plus Atrazine 

Mixtures for Control of Canada Thistle. Weed Science: Vo1.53, No.2, pp. 202-211. 

Herbicide Handbook. 2007. 9th edition. Weed Science Society of America. Triclopyr. Pp 359-

361. 810 E. lOth Street, Lawrence, KS 66044-8897. 

Proprietary Data. 2001-2012. 

Richards, S. P., Buren, L. and L. Glasgow. 2002. Activity ofMesotrione on Resistant Weeds in 

Maize. Pest Manag. Sci. 58(9):981-984. 

USEPA, 2001. Pesticide Fact Sheet- Mesotrione. Available at: 

http://www.e.pa.gov/oppOOOOl/chem search/reg actions/registrationlfs PC-122990 04-

June-Ol.pdf. Accessed date, Dec. 24,2013. 

USEPA, 2010. Review on Justification for the Extension of Exclusive Data Use Period for 

Mesotrione (DP # 361356) 

Ratnayake, S. 2011. USEPA. Review on Justification for the Extension of Exclusive Data Use 

Period for Mesotrione (DP#389857) 

Walsh, M. J., Karrie. S., Kent, S., and S. B. Powles. 2012. Synergistic Effects of Atrazine and 

Mesotrione on Susceptible and Resistant Wild Radish (Raphanus raphanistrum) 

Populations and the Potential for Overcoming Resistance to Atrazine Herbicides. 

Weedscience.org. 2014. International Survey of Herbicide Resistant Weeds. Available at: 

httj?:l/www.weedscience.org/summary/MOA.aspx. Accessed Date, Jan.8, 2014. 

WSSA (Weed Science Society of America, Undated. Summary of Herbicide Mechanism of 

Action. Weed Science Society of America. Available at: http:/ /wssa.net/w.pcontent/uploads/WSSA-Mechanism-of-Action.pdf. Accessed Date, Jan. 6, 2014. 

Page 10 
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 a.i./ 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 capture 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 11