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

### MAR
_17 20111 OFFICE OF CH EMICAL SAFETY AND POLLUTION PREVENTION 

### MEMORANDUM**SUBJE~T:** 

### FROM:

THRU:

TO: Sodium Acifluorfen : Usage Information and Proposed Herbicide Resism:ice {)**~** "'""- Management Measures (PC# 114402).

### ~~ 

## f<--"-'. • 

## d Sunil Ratnayake, Ph.D. , Biologist 

## L , . c 

## W;IJ
.**C~** ' l William Chism, Ph
.D., Senior Biolo · / ·**~** n( / •hk '**~** Jonathan Becker, Ph
.D. , Senior Science Advisor 

## J/,'lc.LJ**~** 

# 'of{**7]0,, 1""""~**  Biological Analysis Branch

-- Stephen Smearman, Economist

# ~~ Economic Analysis Branch Biological and Economic Analysis D ivision (7503P) Colwell Cook, Ph.D., Acting Branch Chief · 

# fl/lf:A.f!A**~** Biological Analysis Branch 

### /t[,.f ) " 

# O Nfl..

### ~o 

# l w/))..**~** 

# k__ Timothy Kiely, Chief 

# u**~** Economic Analysis Branch Biological and Economic Analysis ivision ( P) Nathan Sell, Chemical Review Manager Kelly Sherman, Chief Risk Management and Implementation Branch III Pesticide Reevaluation Division (7508 P) 

### BEAD Product Review Panel Date: March 2, 2016 I

Page 1

### SUMMARY This document describes the use and usage ofthe herbicide sodium acifluorfen which is undergoing registration review in the pffice of Pesticide Programs (OPP). Sodium acifluorfen was first registered as a pesticide in the U
. S
. in 1980 (USEPA, 2004). It is a selective herbicide used for the control ofbroadleaf and grass weeds. Depending on the crop, sodium acifluorfen is applied as pre or post emergence treatments at different growth stages of crops such as soybeans , peanuts, rice, and strawberries. It is a valuable herbicide for the control of weeds in peanuts with 17% ofthe crop treated annually. While aerial application is pennitted on all registered crops, Market Research Data indicate that sodium acifluorfen is applied aerially only on rice and soybeans. Aerial applications on rice and soybeans accounts for 10% ofthe total acres treated with sodium acifluorfen per**y~ar.** To address the spread of herbicide resistant weeds the Agency is proposing weed resistance management elements during the registration review process . This is a tiered approach where the situations (i.e
. the interaction ofthe mechanism of action , resistant weeds, and weed management**strat~gies)** with the least concern for herbicide resistant weeds will have the fewest number ofresistance management elements and the situations with the highest concern will have the most resistance management elements. In addition to the sodium acifluorfen docket, a PRN will be issued shortly to provide guidance to registrants on the Agency's herbicide resistant management approach. All stakeholders are encouraged to submit comments . Public comments received from the chemical specific docket will be considered prior to the Agency's final decision on sodium acifluorfen. Sodium acifluorfen acts to inhibit the protoporphyrinogen oxidase (PPO) enzyme, a key enzyme in the production ofprecursor molecules needed for photosynthesis. PPO inhibitors also result in the formation ofhighly reactive molecules that attack and destroy lipids and protein membranes
. This herbicide is classified by the Weed Science Society ofAmerica (WSSA) as belonging to mechanism of action (MOA) Group 14. This MOA has three confirmed herbicide resistant weeds. This MOA is of moderate concern for weed resistance development because ofthe existing cases ofconfirmed herbicide resistant weeds. Currently there are no herbicide resistant crops . Proposed herbicide resistance management elements for sodium acifluorfen are described herein. 

### BACKGROUND FIFRA Section 3(g) mandates that EPA periodically review the registrations of all pesticides to insure that they do not pose unreasonable adverse effects to human health and the environment
. This periodic review is necessary in light of scientific advancements, changes in policy, and changes in use patterns that may alter the conditions underpinning previous registration decisions. In determining whether. effects are unreasonable, FIFRA requires that the Agency consider the risks and benefits of any use ofthe pesticide. Page2OPP has completed human health and ecological risk assessments for sodium acifluorfen
. No human health ri
. sks were identified
. Ecological risks were evaluated for non-target plant species, fish and birds. For non-target plant species , risks were found in areas adjacent to treated fields due to spray drift. Aerial applications typically pose the greate st risk since the drift is more likely and more widespread
. Other variables that may affect risk drivers in the risk as sessment include application rates, droplet size, and boom height. Sodium acifluorfen was first registered as a pesticide in the U
. S
. in 1980 (USEPA, 2004). The registration review docket for sodium acifluorfen (EPA-HQ-OPP-2010

- 0135) opened in March 2010. Sodium acifluorfen is a s elective , po s t
-emergent contact herbicide regi s tered for use to control annual broadleafweeds and some grasses in soybeans, rice , peanuts, and strawberries. There are currently no registered residential uses . Sodium acifluorfen is a member ofthe di

phenyl ether group ofherbicides and it belongs to a class ofcompounds , light dependent peroxidizing herbicides (LDPH) , known to have a phototropic mode ofaction in plants. LDPHs act in plants through inhibition ofthe enzyme protoporphyrinogen oxidase, leading to cell membrane disruption through reactive oxygen species in the presence oflight. The registered sodium acifluorfen products are liquid concentrates , which are applied using ground or aerial equipment. Also, sodium acifluorfen is formulated or packaged with other herbicides , such as bentazon, imazaquin, sethoxydim, or glyphosate. Sodium acifluorfen can be applied using an aircraft, boom sprayer, and other ground application equipment. 

### USAGE Sodium acifluorfen is applied to approximately one million acres ofcropland annually in the United States (Market Research Data, 2010-2014). The crops that are most dependent on sodium acifluorfen in terms of average percent crop treated (PCT) include peanuts (17%) and rice (5%)
. For soybeans about 1% ofthe crop is treated on average which accounts for about 800 ,000 acres ofthe one million acres treated annually with sodium acifluorfen
. For the years 2013 and 2014, reported use of sodium acifluorfen use on soybeans has increased dramatically
. The number of soybean acres treated increased to approximately 2.2 million acres in 2014 compared to approximately 200,000 thousand treated in 2012
. In terms ofpounds applied, between 2004 and 2012 , the average annual pounds (lbs) active ingredient (AI) applied were as follows : peanuts (50,000 lbs Al/year), rice (20,000 lbs Al/year), and strawberries (500 lbs AI/year)
. For soybeans the average pounds applied from 2004 to 2012 was 80,000 lbs AI/year. However, the average number ofpounds applied for soybeans over the time period from 2010 to 2014 jumped to 800,000 lbs AI/year reflecting substantial increases in the number ofpounds ofactive ingredient applied in 2013 and 2014
. During the 2004 to 2012 time period
. , on average, one application of sodium acifluorfen was applied per year to these registered uses . More recently, between the years 2009 to 2013, 2
. 5% oftreated peanuts, 4.6% oftreated rice, and 10% oftreated soybeans, received an annual average oftwo applications. Information on the use of sodium acifluorfen is presented in Table 1
.

Page3

### Table 1. Sodium Acifluorfen : Average versus Maximum Nu mber of Applications and A lication Rates

Peanuts 1, 228 ,001 2 09 , 634 17 0
. 375 0
.240 Rice 2 , 878 , 190 12 0, 254 5 0.183 Rice 0 .25 

### Arkansas 1, 356,795 86 ,749 6 .5 0
. 188 Soybeans 78,243 , 010 866,550 0
. 3 75 0.265 Strawberries 58,000 5 5 < I 0.354 Strawberr ies 0 .3 75

·chi an 720 55 8% 0.354 Market Research Data, 2010-2014
. Numbers have been rounded
. *EPA, EFED Label Data Report, 2009 Table 2 below provides information on aerial applications for s odium acifluorfen
. While aerial application is permitted for all labeled crop s , Market Research Data indicate that sodium acifluorfen i s applied aerially to two crops only, rice and soybeans. Aerial application to rice and soybeans accounts for 10% ofthe total acres tr eated with sodium acifluorfen per year. Most of the aerial applications of sodium acifluorfen are made on rice with an average ofup to 83 , 000 acres treated annually. Thi s accounts for approximately 70% ofthe acres treated aerially with sodium acifluorfen annually from 2010

- 2014. For soybeans , aerial applications are made on about 33 , 000 acres treated on average , which ·accounts for the remaining 30% ofthe acres treated aerially with sodium acifluorfen annually from 2010-2014 (Market Research Data, 2010-2014)
. On average, 4% ofthe s odium acifluorfen applied to soybeans is made aerially , while approximately 

### 66% ofthe sodium acifluorfen applications to rice are made aerially. Aerial applications are ma de to accommo date wet or overgrown field s that are unable to be entered by foot or ground machinery. For weed control in st rawberries, sodium acifluorfen is typically applied using ground equipment as a band application during renovation (over the top of straw mulch) or after transplanting the plants (before laying plastic mulch). Of all the rice acres treated aerially, Arkan sas accounted for 75% ofthe rice aerial applications with sodium acifluorfen followed b y Missis s ippi and Louisiana with about 12% each and Texas with approximately 2%
. For ground applications, California accounted for approximately 85% of sodium acifluorfen applied to rice followed by Arkansas with 10%
.

Page4

### T bl 2 P a e 

# . ercen o o 1um Cl UO 

### en rea e 

### v 1r
. t 

### f 

### S d
. A 

# ·o rfi 

### T t 

### dB A
. Average Average Average Percent Percent of the Crop Total Acres Acres Treated of Crop Acres Sodium Treated Aerially Treated Aerially Acifluorf en Applied Aerially Rice 125,488 82 , 831 66% 70% Rice (Arkansas) 90,820 67,745 75%* 60% Sovbeans 952 , 178 3 3 , 076 4% 30% Market Re s earch Data, 2010

-2014
. *Arkansas rice acres treated aerially ac counted for approximately 84% ofthe total rice acre s with aerial treatments . 

### Recommended Application Rates a nd Timing Sodium acifluorfen is applied on peanut as a pre-emergence treatment (before the emergence o f crop) or early post and late post treatmens (after the crop emergence) with no more than 0
. 5 lb s AI applied per acre per season . For rice, the recommended application timing is from three leafto ear ly boot ·stage (Acifluorfen 2L Product label , 2012)
. The maximum application rate for rice is 0
. 25 lbs AI per acre per season (Acifluorfen 2L Product label , 2012)
. According to the label recommendation, sodium acifluorfen s hould not be applied on rice after the boot stage. This is a growth stage after the establishment ofpermanent flood and generally , permanen t flooding is established 4 weeks after planting. N ot more than two applications should be made on rice per season. Prior to application , the rice crop must pass the 3-leaf stage. On the basis ofMarket Research Data, the highest amount of sodium acifluorfen applied on rice is for late post-applications, which i s three weeks after planting or later . For soybean , sodium acifluorfen is applied as a pre-plant bum

-down treatment prior to planting. 

### In addition, sodium·acifluorfen is also applied on soybean at the early growth stage ofweeds
. This is mostly during the two to s ix leaf stage ofweeds depending on the weed species
. According to the product label , not more than 0
. 5 lbs AI per acre per season s hould be applied on soybean
. The second application of sodium acifluorfen i s as a late post application to manage new flushes ofweed populations during the mid-season
. According to Market Re search Data the most usage of sodium acifluorfen on soybean is applied as lat e post applications , which is three weeks after planting or later
. There must be a minimum of 15 day appFcation intervals between two applications. For weed control in strawberries sodium acifluorfen is appli ed as a band application after the final land preparation
. However this application must be made before laying plastic mulch and transplanting the crop (Acifluorfen 2 Product label, 2012)
. On strawberries only ground equipment i s used to apply sodium acifluorfen and the maximum application rate for strawberrie s is 0
. 375 lbs AI per season (Acifluorfen 2L Product label , 2012, Registration no . 82534-2-88783)
. .
Page 5

### Ap plication Rates and Number of
. Applications of Sodium Acifluorfen There were three crops to which sodium acifluorfen was applied multiple times per year between 2010 and 2014. Peanuts, rice, and soybeans each had up to 2 applications per year. For peanuts, rice and soybeans, about 2% , 4
. 5% and 8% of the acres respectively, report two applications (Market Research Data, 2010-2014)
. Strawberries acres received only one application of sodium acifluorfen seasonally. The maximum, average and upper bound application rates and the percent ofacres treated multiple times for peanuts, rice, soybeans and strawberries is presented in Table 3. 

### In terms ofthe application rate for each crop, approximately 95% ofthe peanut acres are treated at a rate equal to or below 0.25 lbs Al per acre with an average single application rate of0
.233 lbs AI per acre well below the single maximum application rate of0.375 lb s AI per acre. For rice, approximately 70% ofthe acres are treated at a rate equal to or below 0
.20 lbs AI per acre with an average single a pplication rate of 0.175 lbs AI per acre which is also well under the maximum single application rate of 0
.250 lbs AI per acre. For soybean , about 80% ofthe soybean acres are treated at a rate equal to or below 0.25 lbs AI per acre with an average single application rate of 0
.241 lbs AI per acre , also well under the maximum single application rate of 0.375 lbs AI per acre. For strawberry, approximately 70% ofthe strawberry acres that are treated with sodium acifluorfen, are treated at the single maximum rate of 0.375 pounds AI per acre. The average single applicat ion rate is 0.354 pounds AI per acre with 0% ofthe acres treated multiple times. All ofthe sodium acifluorfen use reported on strawberry is from Michigan.
. The reported use and rates indicate that the majority of acres are treated at rates below the maximum (which are used in the risk assessments). Thus, the risks identified in the risk assessments are unlikely to be realized in field situations. (See Table 3) 

### T b l 3 A Ii f 

### Ra

a e 

# . .pp ca 1 0 0 

### tes andMJ"JA Ii 

### f S d " A ifl rfi 

### b C u tip
.e .pp cations o o mm c uo en 1 y 

### rop . *Maximum Single Average Single Upperbou nd Rate Cr op Application Rate Applicatio n Rate (%o f Acres (lbs Al/acre) (lbs Al/acr e) Tr eated) -95% at**0.25** lbs Peanuts 0 .3 75 0
.233 AI/acre

- 70% at**0.2** lbs Rice 0.250 0
. 175 AI /acre

- 80% at**0.25** Soybeans 0.375 0.241 lbs AI/acre

- 70% at 0 .37 5 lbs Strawberry 0.375 0
. 354 AI /acre Market Research Data, 2010-2014
. Numbers have been ro unded
. *EPA, EFED Label Data Report, 2009

Page6 % of Acres Treated Mult iple Times 2.0% 4.5%

8% 0%

### Target Pests of Sodium Acifluorfen Sodium acifluorfen controls many annual broadleafweeds such as momingglory (lpomea spp.), black nightshade (Solanum nigrum), cocklebur (Xanthium strumarium), ragweed (Ambrosia artemisiifolia) , smartweed (Polygonum spp.), wild buckwheat (Polygonum convolvulus) and wild mustard (Sinapis arvensis) species (WSSA, 2014)
. Also, sodium acifluorfen at higher rates can be applied to control several grass weed species such as seedlingjohnsongrass and foxtail species (WSSA , 2014). Hemp sesbania (Sesbania exaltata), redstem (Ammannia baccifera), and barnyardgrass (Echinochloa crusgalli) are the most troublesome weeds in rice production. Sodium acifluorfen is recommended for common annual weed species found in the rice production fields, especially for the control ofhemp sesbania, and redstem, (Texas Rice Production Guide Lines, 2014)
. Major weed species found in peanut production are morning-glory species (lpomoea spp.), Hemp sesbania (Sesbania exaltata), sicklepod (Cassia obtusifolia), and Palmer amaranth (Amaranthus Palmeri) , (Market Research Data)
. Major weeds species found in soybean production are red root pigweed (Amaranthus retroflexus) , morning glory (lpomoea spp.), common waterhemp (Amaranthus
. rudis), hemp sesbania, and s icklepod
. (Market Research Data). Some ofthese weed species are resistant to glyphosate and ALS inhibiting herbicides**(He~p,** 2016). In recent years, the use ofPPOinhibitors has increased, especially for controlling glyphosate- and ALS-resistant weeds in soybean (Legleiter et al
. , 2009)
. 

### Droplet Size and Efficacy of Sodium Acifluorfen The droplet size effects the efficacy and off site 

### drift ofa pesticide application. The optimum droplet size for any herbicide or plant growth regulator is not something that can be generalized; rather, it should be selected based on data and knowledge
. Deposition ofthe most effective amount of active ingredient on**pl~t** foliage and reduction ofoff-site 

### drift are the major objectives of selecting an optimum
. droplet size. In some cases, droplet size and application rates are correlated; that is, coarser droplets are associated with higher application rates to maintain efficacy. However, 

### in some systemic herbicides or defoliants, coarse droplet size with less coverage will still allow effective control. The optimum droplet size is impacted by chemical/physical parameters ofthe pesticide and other factors such as drying ofthe chemical prior to actual uptake and 

### air pressure used 

### in the application. In addition, the interaction of concentration and plant uptake, and**th~** interaction ofthe active ingredient with other chemicals in a 

### tank mixture are some ofthe other Jactors that should be considered on selection ofoptimum droplet size. BEAD has limited information on the relationship of droplet size and efficacy for sodium acifluorfen. 

### RESISTANCE MANAGEMENT The development and spread ofherbicide resistant weeds 

### in agriculture is a widespread problem that has the potential to fundamentally change production practices in US agriculture
. While Page7herbicide resistance weeds have been known since the 1950s, the number of species and their geographical extent, has been increasing rapidly
. Currently there are 249 weed species worldwide with confirmed herbicide resistance, especially since the turn ofthe century . In the United States there are 155 weed species with confirmed resistance to one or more**herbicid~s.** Management ofherbicide resistant weeds, both in mitigating established herbicide resistant weeds, and in slowing or preventing the development of new herbicide resistant weeds is a complex problem without a simple solution. Coordinated efforts ofgrowers, agricultural extension, academic researcher, scientific societies, pesticide registrants, and state and federal agencies are required to address this problem. In September 2-014, the Weed Science Society ofAmerica sponsored an international meeting,
. the Herbicide Resistance Summit Il , hosted by the National Research Council (WSSA, 2014). This meeting was organized to facilitate a more unified understanding ofthe herbicide resistance issues across the country, understanding ofdifferences ofviewpoints, and approaches to solutions. The meeting was attended in person or via webinar by participants from approximately 100 locations across the United States , Australia, Canada and Germany , underscoring the significance and widespread nature ofthis problem and its impact on agricultural productivity. The Agency announced at this meeting that it would take a more proactive role in developing regulatory approaches for managing resistant weeds (Housenger, 2014)
. Shortly after this meeting, the Secretary ofA¢culture announced USDA 's herbicide resistance actions that were developed in collaboration with the Environmental Protection Agency (USDA , 2014)
. The EPA, Office of Pesticide Programs (OPP) is proposing measures for the pesticide registrants to provide gro wers and users with detailed information and recommendations to slow the development and spread ofherbicide resistant weeds. This is part ofa more holistic, proactive approach recommended by crop consultants, commodity organizations, professional/scientific societies, researchers, and the registrants themselves. OPP's approach is measured, based on the inherent risk ofweed resistance developing for a given herbicide, considering the tar get weeds and the agronomic practices ofthe registered crops. Situations with the least concern for the development of herbicide resistant weeds will have the fewest resistance management elements and the situations with the highest concern will have additional resistance management elements
. Additional details are provide in the attached appendices, as follows: Appendix I

- Guidance for**Pe~ticide** Registrants on Pesticide Resistance Management Labeling (EPA, 2001)

. Appendix II-Definition ofResistance and Likely Resistance

Appendix III

- Best Management Practices for Herbicide Re s istant Weed s (from the Herbicide Resistance Action Committee and the Weed Science Society ofAmerica
.

Page 8

### Implementation Timeline and Opportunities for Public Comment on Herbicide Resistance Approach OPP is proposing to implement herbicide resistance**m~asures** for existing chemicals during registration review, and to implement herbicide resistance measures for new chemicals and uses at the time ofregistration. In registration review, proposed herbicide resistance elements will be in every herbicide preliminary interim decision. Comments on these chemical specific measures are welcomed. In addition, OPP will issue a PRN that will provide registrants with addition guidance. All stakeholders are encouraged to comment on the herbicide resistance management approach, rationale , and proposed elements
. Public comments received concerning the sodium acifluorfen docket and the PRN docket will be considered prior to the final decision on sodium acifluorfen. 

### Herbicide Resistant Management Concerns with Sodium Acifluorfen Sodium acifluorfen acts to inhibit tl?.e protoporphyrinogen oxidase (PPO) enzyme , a key enzyme in the production ofprecursor molecules needed for the photosynthesis. PPO inhibitors also result in the formation of highly reactive molecules that attack and destroy lipids and proteins membranes. This herbicide is classified by the Weed Science Society ofAmerica (WSSA) as belonging to mechanism ofaction (MOA) Group 14. This MOA has three confirmed herbicide resistant weeds
. This MOA is ofmoderate concern for weed resistance development because ofthe existing cases ofconfirmed herbicide resistant weeds. Currently there are no protoporphyrinogen oxidase (PPO) resistant crops . Therefore , registrants should address elements one through eight in Table 4. Table 4 lists the complete set ofresistance management elements that can help slow the spread ofherbicide resistant weeds and Table 

### 5 indicates which elements should be addressed based on mechanism of action (MOA) and use on herbicide resistant crops. These elements include instructions for the user, label language, and instructions to the registrant.

Page9

### Table 4. Elements ofResistance Manae:ement or Stewardship Plan. 

### Element Description 1



### 2

3

4



### 5

6

7



### 8 List Mechanism of Action (MOA) Group Number. • This information is critical to allow the user to rotate between effective MOA's to reduce the buildup ofresistant pests. );> Registrant is responsible for placement on label. List seasonal and annual maximum number of applications and amounts . • This information is critical to allow the user to know how many applications and amounts can be applied in order to develop an effective IPM plan for the season and the entire year. );> Registrant is responsible for placement on label. Resistance Management language from PR Notice 2001-5, and/or Best Management Practices (appropriate to crop) from Weed Science Society of America (WSSA) 

### & Herbicide Resistance Action Committee (HRAC), and/or HRAC proposed guidelines for herbicide labels. • This is an educational opportunity to remind users to look for and follow a resistance management plan. 

## > Registrant is responsible for placement on label. User should scout before and after application. • Reminding the user to scout can help insure that the proper pesticide is applied based on the weed species and growth stage and determine ifthe pesticide applied provided effective control. · 

# > Registrant is responsible for placement on label. 

## > User is responsible for following the recommendations. Definition of Likely Resistance
. • It can take up to five years to confirm herbicide resistance. By describing likely resistance users could proactively identify and attempt to control weeds in the early stages before they become widespread in their fields. 

# > Resristrant is responsible for placement on label. User should report lack ofperformance to registrant or their representative. • Reporting lack ofperformance can help provide the user with additional resources for the identification and control ofproblem weeds
. In some cases lack ofperformance could be an ear ly indication of likely resistance and contacting the registrant can help insure the weed is controlled before resistance becomes widespread in their fields
. 

# > Registrant is responsible for placement on label. 

## > User is responsible for following the recommendations. List confirmed resistant weeds in a separate table and list effective or recommended rates for these weeds with the table. • This is an educational opportunity to clearly indicate which weeds are prone to resistance and remind the users to select the correct rates for their crop and site. 

## > Registrant is responsible for placement on label. Registrant report new cases oflikely and confirmed resistance to EPA and users yearly. This will be in addition to any adverse effects reporting. • · This will allow the information likely and confirmed resistance to be Page 10available in a timely manner to users , consultants, extens ion, etc . so that the y are aw are of and proactively addres s the problem
. 

# • Provide weed species, crop or site, state , and herbicide used
. );> Recistrant i s responsible for reporting. For s ites ofhigh concern provide growers with :

0 Resistance Management Plan 0 Remedial Action Plan (to control res istant weeds this season or next season) 0 Educational materials on resistance management. 9 

# • Plans should be locally dev eloped and easily modified
. EPA recommends that registrants work with Extension, Consultants , Crop Groups, HRAC , & USDA
. 

# • This i s an educational opportunity to remind users ofthe importance of resistance management. );> Registrant is responsible for creating or providing educational material s. For combination products with multiple MOA, list which herbicide is controlling which weed (a 3 w ay mixture may only have 1 effective MOA for some problem weeds)
. List minimum recommended rate 

### ifre s i stance i s suspected
. 

# • Using a combination products with only one effective MOA can select for 10 herbicide re s istant w eeds
. 

# • Thi s will allow users to select herbicide combinations with multiple effective MOAs for the problem weeds on their fields
. 

# • Registrant i s responsible for placing the list on label or otherwi se providing the information
. Any addit i onal specific requirements (e .g. mandatory crop rotation, unique agron omic aspects , additional training, time limited registration, etc.). 

# • During discussions with the Agency other elements may be deemed 11 appropriate to help reduce s the spread ofresistance. 

# • The elements may be on the label , the technical use agreement for the seed trait, or as a reporting requirement. );> Rel?istrant is responsible
. 

### Footnote: Mechanism ofAction Group number comes from the WSSA , definition ofresi stance and likely resistance, PR Notice 2001-5 and BMP language are 

### in Appendix 1-3. Resistance elements for fungicides and insecticides
.

Page 11

### Table 5. Herbicide Resistance Catffones of Concern*

MOA ' s with no resistance weed species in the U
. S.
1
. MOA on Label 2. List seasonal and 

### annual maximum number of applications and pounds 3. Resistance management language from PRN 2001-5 or BMPs 4. Scout before and after application 

# - - -

MOA ' s with a few resistant

weed species in the U.S.
Elements 1 through 4 plus 5
. Definition of likely and confirmed resistance 6
. Farmer should report lack ofperformanc
. e to registrant or its agent 7. List confirmed resistant species in separate table and list effective or recommended ·rates for these weeds with the table 8
. Registrant report new cases oflikely and confirmed resistance to EPA & users yearly ,.. 

# .. _ ' -. Higfi 

### eoncern .,, • Any new herbicide with a new or

novel mechanism ofaction, or • Herbicides for which resistant

crop(s) have been developed (conventionally bred or GM), or • MOA's with most resistant weeds

in U
. S. Elements 1 through 8) plus · 

### 9. Provide growers with : Resistance Management Plan, Remedial Action Plan, Educational materials on resistance management 10. For combination products with multiple MOAs , list which herbicide is controlling which weed and minimum recommended rate 11. Any additional specific requirements (e.g. mandatory crop rotation, unique agronomic aspects, time limited · relristration, etc.)
. 

# * Ifnew resistant weed species are found a MOA may move to higher level ofconcern.



### REFERENCES Acifluorfen 2L. Product Label (EPA Reg
. No
. 82534-2-88783). 2012
. Summit Agro USA, LLC. 8000 Regency Parkway Suite 285, Cary, NC 27518. Online Publication
. Available at: http://www.agrian .com/pdfs/Acifluorfen 2L Label.pdf. Accessed on March 3 , 2016. BEAD, 2014
. Acifluorfen Screening Level Usage Analysis (SLUA). Biological and Economic Analysis Division, Office ofPesticide Programs, US Environmental Protection Agency
. July 7, 2014. EPA
. 2001. Guidance for Pesticide Registrants on Pesticide Resistance Management Labeling
. Pesticide Registration (PR) Notice 2001-5. http: //www.epa. gov/s ites/ production/files/20l4-04/do cuments/pr200 1-5 .pdf. Fraser, K. 2013. Glyphosate resistant weeds intensifying
. Accessed online on July 23 , 2015 at http:// stratusresearch.com/blog/glyphosate-resistant-weeds-intensifying
. Page 12Heap, 

### I. 201 6. The Internatio nal Survey**ofHerbi id~**  Resistan t Weeds. Online
. Internet. Tues day, November 10, 2015. Available at : www.weed science.org. Access ed on March 4, 2016
. HR.AC
. 2015. Herbic ide Res i s tance Management, Proposed HR.AC Stewardship Guideline s for Herbicide Labels. Accessed online on September 24, 2015 at http: //www. hracglobal .com/ p ages/hrac stewardshi p guide linesforherbicidelabels.aspx Acces sed on March 3 , 2016. Legleiter, T. R. , & Bradley, K. W. (2008). Glypho sate and multiple herbicide resistance in common waterhemp (Amaranthus rudis) popula tions from Missouri. Weed Sci. , 56 , 582

- 587
. http://dx
. doi.org/1O .l 6 l 4/WS-07

- 204.1
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### J. Fernandez-Cornejo , 

### J
. Unger, C
. Osteen, D. Schimmelpfennig , T. Park, and D. Lambert
. 2015
. The Economics of Gl

y

phosate Resistance Management in Corn and Soybean Produc tion , ERR-184, U
. S
. Department ofAgriculture, Economic Research Service, April 2015. Market Res earch Data
. 2010-2014. Data collected and sold b y a private market re search 

### firm
. Data collected on pesticide use for about 60 crops by annual surveys ofagricultural users in the continental United States
. Survey methodology provides stati stically valid results , typically at the state level. Norsworthy, J
.K., S. M. Ward , D. R. Shaw, R. S
. Llewellyn, R. L. Nichols, T. M
. Webster, K
. W. Bradley , G
. Frisvold, S
. B
. Powles , N. R. Burgos , W
. W. Witt, and M
. Barrett. 20 12
. Reducing the Ri s ks ofHerbicide Res istance : Best Management Pr actices and Recommendations
. Weed Science 2012 Special Issue : 31-62. Available online at: http :/ /www.wssa j ournals.org/doi/ pdf/l 0. 1 6 14/ WS

-D- 11 -00155.1
. Accessed on March 4 , 2016
. Ratnayake, S. 2015. Rice Production Practices in the United States and Use ofCyhalofop-butyl for Weed Control in Rice Product ion , Revi sed (DP# 420989)
. Publication ofUSEPA. Biological and Economic Analysis Divi sion
. Shaw, D.R. , W. H. Morris , Webster, E. P ., and D
. Smith
. 2000. Effects of Spray Volume and Droplet Size on Herbicide Depo sition and Common Cocklebur Control. Weed Technology, Volume 14:321-326
. Accessed on March 4 , 2016. · Texas Rice Product i on Guidelines
. 2014
. Texas A& M Agri life Extension. Texas A&M University
. Onl
. ine Publication
. Available at : http: //extento pub s. tamu .edu/ pdf/2014 Ri ce Production Guidelines. pdf
. Accessed on October 30, 2015
. · University ofArkansas. 2013. Arkansas Rice Production Handbook. University of Arkansas Division ofAgriculture. Available at : http: //www.uaex
.edu/ pub lications/pdf /mp l 92/mpl92.pdf. Accessed on November 11 , 2015
. . Page 13USEPA (United States Environmental Protection Agency). Office ofPesticide Programs
. 2004. Online Publication
. Available at: http ://www3. epa . gov / pesticide s/chem search/ re g actio ns/ rereg i stratio n/ red PC

114402 24-Feb- 04
.pdf Accessed on Nov
. 11, 2015. Weed Science Society ofAmerica. 2014. Herbicide Handbook 10th edition.

Page 14

### APPENDIX 

### I. Guidance for Pesticide Registrants on Pesticide Resistance Management La . beling (EPA, 2001) 

### Herbicides 1. The following general resistance management labeling statements are recommended for herbicide products containing only a single active ingredient or only active ingredients from the same group:
a ."For resistance management, (name ofproduct) is a Group (mode ofaction group number) herbicide. Any weed population may contain or develop plants naturally resistant to (name ofproduct) and other Group (mode ofaction group number) herbicides. The resistant biotypes may dominate the weed population ifthese herbicides are used repeatedly in the same field. Other resistance mechanisms that are not linked to this mode ofaction but are specific for individual chemicals, such as enhanced metabolism, may also exist. Appropriate resistance-management strategies should be followed." For products containing active ingredients from different groups, the statement should be modified to reflect the situation,**f~r** example : b. "For resistance management, please note that (name ofproduct) is both a Group (mode of action group number) and a Group (mode of action group number) herbicide. Any weed population may contain plants naturally resistant to Group (mode ofaction group number) and/or Group (mode ofaction group number) herbicides. The resistant individuals may dominate the weed population ifthese herbicides are used repeatedly in the same fields. " 2. The following additional resistance management labeling statements are recommended for herbicides, although each bulleted statement may not be appropriate or pertinent for every product label:

" To delay herbicide resistance:
a . Rotate the use of (name ofproduct) or other Group (mode of action group number) herbicides within a growing season sequence or among growing seasons with different herbicide groups that control the same weeds in a field. b. Use 

### tank mixtures with herbicides from a different group if such use is permitted; Use the less resistance-prone partner at a rate that will control the target weed(s) equally as well as the more resistance-prone partner.
c. Adopt an integrated weed management program for herbicide us e that includes scouting and historical information related to herbicide use and crop rotation, and that considers tillage (or other mechanical control methods), cultural (e.g., higher crop seeding rates; Page 15precision fertilizer application method and timing to favor the crop and not the weeds), biological (weed-competitive crops or varieties) and other management practices. d. Scout after herbicide application to monitor weed populations for early signs ofresistance development. Indicators ofpossible herbicide resistance include: (1) failure to control a weed species normally controlled by the herbicide at the dose 

### applied, especially 

### if control is achieved on adjacent 

### weeds; (2) a spreading patch ofnon-controlled plants ofa particular weed species ; (3) surviving plants mixed with controlled individuals ofthe same species. If resistance is suspected, prevent weed seed production in the affected area by an alternative herbicide from a different group or by a mechanical method such as hoeing or tillage
. Prevent movement ofresistant weed seeds to other fields by cleaning harvesting and tillage equipment when moving between fields , and planting clean seed
. e. 

### Ifa weed pest population continues to progress after treatment with this product, discontinue use ofthis product, and switch to another herbicide with a different target mode of action, 

### if available. f. Have suspected resistant weed seeds tested by a qualified laboratory to confirm resistance and identify alternative herbicide options. g . Contact your local extension specialist or certified crop advisors for additional pesticide resistance-management and/or integrated weed-management recommendations for specific crops and weed biotypes
. h
. For further information or to report suspected resistance, contact (company representatives) at (toll free number) or at (Internet site)."


### APPENDIX II. Definition ofResistance and Likely Resistance According to the Weed Science Society ofAmerica "Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose ofherbicide normally**leth~** to the wild 

### type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or selection ofvariants produced by tissue culture or mutagenesis." "Herbicide tolerance is the inherent ability ofa species to survive and reproduce after herbicide treatment. This implies that there was no selection or genetic manipulation to make the plant tolerant; it is naturally tolerant." (http: // weedscience
. org/ documents/ res is tancecriterion
.pdf).
Indicators of likely herbicide resistance (called possible resistance in Norsworthy et al 2012, Page 39) inchide (1) failure to control a weed species normally controlled by the herbicide at the dose applied, especially if control is achieved on adjacent weeds; (2) a spreading patch of noncontrolled plants ofa particular weed species; and (3) surviving plants mixed with controlled individuals ofthe same species.
Page 16

### APPENDIX III. Best Management Practices for Herbicide Resistant Weeds Crop Selection and Cultural Practices: 1. Understand the biology ofthe weeds present. 2. Use a diversified approach toward weed management focused on preventing weed seed production and reducing the number ofweed seeds in the soil seed-bank. 3. Emphasize cultural practices that suppress weeds by using crop competitiveness. 4. Plant into weed free fields , keep fields as weed free as possible, and note areas where weeds were a problem in prior seasons. 

### 5. Incorporate additional weed control practices whenever possible, such as mechanical cultivation, biological management practices, crop rotation , and weed-free crop seeds , as part of an integrated weed control program. 6. Do not allow weed escapes to produce seeds , roots or tubers
. 7. Manage weed seed at harve st and post-harvest to prevent a buildup of the weed seed-bank. 8. Prevent field-to-field and within-field movement ofweed seed or vegetative propagule s . 9
. Thoroughly clean plant residues

- from equipment before leaving fields. 10
. Prevent an influx of weeds into the field by managing field borders. 11. Fields should be scouted befo re application to ensure herbicides and application rates will be appropriate for the weed species and weed sizes present. 12
. Fields should be scouted after application to confirm herbicide effectiveness and to detect weed escapes. 13. 

### Ifresistance is suspected, treat weed escapes with an alternate mode of action or use nonchemical methods to remove escape s . 14
. Avoid outcro s sing to weedy**ela~ives ,**  in crops that outcross . Control weedy relatives 

### in surrounding field margins
. Research has demonstrated that the pollen can move __ feet. 

### Herbicide Selection: 1. Use a broad spectrum soil applied herbicide with a mechanism of action that differs from this product as a foundation in a weed control program . 2
. A broad spectrum weed control program should consider all ofthe weeds present in the field. Weeds should be**iden~fied** through scouting and field history. 3
. Difficult to control weeds may require sequential applications ofherbicides with alternative mechanisms ofact ion. 4. Fields with difficult to control weeds should be rotated to crops that allow the use of herbicide s with alternative mechanisms ofaction. 

### 5
. Apply full rates ofthis herbicide for the mos t difficult to control weed in the field
. Applications should be made when weeds are at the correct size to minimize weed escapes. 6. Do not use more than two applications of''this**herbicid~'~** or any herbicide with the same mechanism ofaction within a single growing season unless mixed with another mechanism ofaction herbicide with overlapping spectrum for the difficult to control weed s . 7. Report any incidence ofnon-performance ofthis product against a particular weed species to the representative (list contact information here). · 

### Footnote: Most items are taken from the Herbicide Re s istance Action Committee I Weed Science Society ofAmerica list ofBest Management Practices. Page 17