UNITED STATES ENVIRONMENT AL PROTECTION AGENCY WAS HINGTON D .C

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OFF I CE OF C H EM I CAL SAFET Y AND POLLUTI ON PRE V

ENTI ON

MEMORANDUM

SUBJECT:


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TO: Bentazon Usage Information (PC# 103901)
Caleb Hawkins , Environmental Protection Specialist //**~** Biological Analysis Branch

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## {~**~** Rafael Prieto, Environmental Protection Specialist**/J ~A**  

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Elizabeth Hill, Economist 

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Colwell Cook , Acting Chief

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# tJBiological Analysis Branch Timothy Kiely, Chief 

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Moana Appleyard, Chemical Review Manager Linda Arrington, Chief Risk Management and Implementation Branch V Pesticide Reevaluation Division (7505P)

BEAD Product Review Panel date: December 16, 2015

### SUMMARY
This document describes the use and usage of bentazon (also referred to as sodium bentazon) , which is undergoing registration review in the Office of Pesticide Programs (OPP). The Biological and Economic Analysis Division (BEAD) is providing information on the use and benefits of bentazon as part of the risk-benefit process which informs the decision phase of registration review. This memo describes key crops where bentazon is used , typical treatment rates , application timing and intervals , information on water holding times for rice, and crops where applications are made by 

### air. This information will be useful in characterizing the risk assessment for bentazon, aiding in the risk management decision, and in informing any risk mitigation measures that are found to be necessary. The primary mitigation measure proposed by OPP that could impact growers is to limit the number ofapplications to one per year across all crops. Typically, no more than one application is made annually, although multiple applications do occur in some limited instances for dry beans/pea, sweet corn, and soybeans. Based on usage data and extension documents , BEAD finds that limiting the number of applications could potentially limit growers ' options for problematic weed control and resistance management.
To slow the spread of herbicide resistant weeds the Agency is requiring weed resistance to be addressed during the registration review process. This is a tiered approach where the situations with the least concern for herbicide resistant weeds (fewest number of herbicide resistant weed species) will have to address the fewest resistance e lements l}lld the situations with the highest concern (highest number ofherbicide resistant weed species) will have to address the most resistance management elements. As the concern for resistance increases more extensive resistance components will be required from the registrant. Bentazon is an inhibitor of photosynthesis at photosystem II site B (Group 6). Bentazon is of moderate concern for resistance because there is at least one weed species resistant to this Mechanism ofAction (MOA) found in the U.S. and there are no bentazon resistant crops grown in the U.S. 

### 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 ofany use ofthe pesticide. OPP has completed risk assessments for bentazon and is considering the risks and benefits to determine if changes to the use directions should be made.
Bentazon is a selective, contact, early post-emergent herbicide registered to control broadleaf weeds and sedges in numerous agricultural field crops and around trees and vines in various fruit and nut crops. Bentazon is also registered for use to control weeds in residential and recreational lawns around ornamental plants. Bentazon is a salt which rapidly dissolves in water to produce a sodium ion and a bentazon acid anion; it is always applied as a spray.

2The Reregistration Eligibi lity Decision document (RED) for bentazon was issued in 1994. In 2000, EPA reassessed tolerances ofbentazon in compliance with the Food Quality Protection Act (FQPA)

. EPA published draft human health and ecological risk assessments in 2014. For the human health assessment, no data deficiencies were identified in either the toxicity or exposure databases and the Agency concluded that bentazon does not pose human health risks. The most recent ecological risk assessment concluded that risks to listed and non-listed terrestrial plants in uplands and semi-aquatic habitats were of concern to the Agency as well as acute risks for small to medium birds that consume plants or small insects, and small mammals that feed on short grass (listed species only). The Agency is considering modifications in the use ofbentazon, such as reductions in the number of annual applications, reductions in application rates, and limiting aerial applications, to reduce potential exposure ofbentazon to terrestrial plants and mammals.
PURPOSE
BEAD is assisting in the registration review decision by providing information to help characterize the risks and benefits ofbentazon, and possible impacts ofmitigation. Possible impacts from increasing droplet size and reducing the number of applications may include yield loss and the encouragement of herbicide resistance in certain problematic weed species. This memo provides information on application rates, application frequency, rice production practices , and herbicide resi stance management.
USAGE & APPLICATION TIMING
Information on usage is presented in Table 1. Bentazon is applied to approximately 1.9 million acres of cropland annually in the United States. The crops that are most dependent on bentazon in terms of percent crop treated (PCT) include dry beans /peas (42% PCT) , peas (33% PCT) , bush beans (31 % PCT), and peanuts (29% PCT ). The maximum seasonal rate across all crops is 2 lb s ai/A whi le the maximum single application rate ranges from 1to1.5 lbs ai/A. Maximum single application rates are not typically applied. Market research data (MRD) from 2009 to 2013 indicates that the average application rate for specific crops ranges from 0.35 to 0.73 lbs ai/A (Table 1).

3Table 1. Bentazon: Average versus Maximum Number of Applications and Application Rates and Rate Distributions, 2009-2013 Avera**::::;;;:r:~'::;:".":'-:-;-,- ~....,..~** **'='="'."""':-: ":':":"'"~"'"'.'""T** **"'."""7'" -:-"-=--** **~-,-.,.,--==:-::-:~~**

256 31% 1.5 0.571
Com 91 ,499 < 1% 1.5 0.614 0.75 Dry 2 , 727 42% I.I 1.5 0.528 Beans/Peas Lima Beans 36 16% 1.5 0

.927 Peanuts 1, 18 3 29% 1. 5 0.438 0.75 Peas (Fresh/ 178 33% 1.5 0.732 Green/ Sweet Rice 2,917 1% 0.500 0.75 Sorghum 6 ,45 8 < 1% 0.349 0.5 Milo Soybeans 76 , 824 < 1% I.I 1. 5 0.480 0.75 Sweet Com 559 4% 1.04 1.5 0.723 MRD, 2009-2013. Numbers have been rounded. l Ninety percent or more ofall application treatments were at the specified rate or lower for each crop listed

. BEAD doe s not have information on the average number ofapplications for all crops. This table doe s not include all ofthe crops for which bentazon is registered. 

### Bentazon Aerial Usage
Table 2 provides information on aerial applications for bentazon. Most aerial applications of bentazon are made on rice (26,4 00 total acres treated annually), or 0.9% of the average number of crop acres grown**annu~ly** from 2009-2013. Aerial applications are also made to dry beans/peas, with 8,200 total acres treated annually, which equates to 0.3% of the average number of total crop acres grown annually from 2009-2013 (Market Survey Data, 2009-2013). Less than one percent of bentazon applied to dry beans/peas were made aerially. In contrast, the vast majority ofbentazon applications to rice were made by air, with over 74% of bentazon applications made aerially. For both dry beans/peas and rice , aerial application rates were slightly higher than the rates used for ground applications ofbentazon, but were still well below the label max rate (the rate used for the risk assessments).

4

### Table 2. Bentazon: National Aerial Applications, Tot.al Area Treated (acres), Percent Crop 

### Treated,-and Application Rate Ob. a.i./acre), 2009-2013 Average

. Total Area Average Aerial Percent of Total Crop Treated Aerially 1 

### Application Rate Area Treated that (acres) (lb/A) is made Aerially2 Dry Beans/Peas 8 , 200 0.533 <1% Rice 26 ,400 0.689 74% MRD, 2009-2013. Numbers have been rounded

. I Total area treated represents the summation of acres treated by a particular chemical, even those acres that have received multiple applications. 2 This column represents all aerial applications made across total acres treated,'even those acres that received multiple applications. This percentage has the potential to s light ly differ in comparison to the percentage ofbase acres treated (i.e., acres treated without regard to the number of applications that occurred) with bentazon; typically only one application ofbentazon is made annually to dry beans/peas and rice , making total acres and base acres treated

- and thus the percent oftotal and base acres treated aerially-similar

.


### Multiple Applications of Bentazon Typically, no more than one application is made annually, although multiple applications do
occur in some limited instances for dry beans/peas , sweet com, and soybeans (Table 1). For dry beans , approximately 150 ,000 acres (13% of acres treated with bentazon) in the United States receive two applications, while a small percentage ofacres have been treated three times. Typically the use of second applications are sporadi c from year to year, with the exception of Michigan and Minnesota where third applications occur regularly on dry beans , accounting for 7% and 15% of base acres treated annually from 2009 to 2013 (Table 3).
For soybeans, usage is sporadic across years for all states in which b entazon usage was reported, with most ofthe soybean acres treated with bentazon in Mississippi receiving two applications (96% ofbase acres treated with bentazon); however, these second applications-and usage of bentazon overall-is mostly limited to a single year. This may be the result of a problematic pest occuring during that time period. Overall, 22% of bentazon base acres treated recevied a second application in the United States (34,908 acres).


### T bl 3 M 1. 1 A I'



### a e 

# . u tip e .pp 1cataons o f 

### B b 

# s entazon •Y 

### tate, 2009 2013 A to vera2e. Dry Beans Percent of Bentazon Treated Acres Base Acres Acres Treated Acres Treated Three Treated More State Treated Twice Times than Once Idaho 25 ,3 83 53 1 0 2% Michigan 110 ,414 7,21 I 0 7% Minnesota I 17 ,434 17,310 451 15 % Montana 11 ,2 71 119 0 1% Nebraska 72,811 821 0 1% New York 6 , 064 64 0 1%
5Dry Beans Percent of Bentazon Treated Acres Base Acres Acres Treated Acres Treated Three Treated More State Treated Twice Times than Once North Dakota 745 ,33 4 123 ,027 17% United States 1, 144,417 149, 08 3 451 13% 

### Sovbeans Arkansas 51 ,277 1, 184 0 2% Mississiooi 31,821 30,537 0 96% North Dakota 26 , 860 3, 187 0 12% United States 157 , 885 34,9 08 0 22% MRD, 2009

-2013. Multiple applications have also historically occurred on sweet com, but detailed in fonnation on multipl e applicati ons is unavailable from MRD (2009

-2013). This tabl e provides national base acr es treated and a li st the tota l acres treated twice. The only states listed in the tabl e are states fo r which BEAD has data on multiple applications. Any mitigation limiting the number of applications to one per season could negatively impact yield and herbicide resistance management in a number of crops. BEAD 's data on multiple applications are limited and may not capture all instances of multipl e app lications to control problematic weeds. Extens ion documents identify sequential, lower rate applications in a number ofcrops and for spec ific problematic weeds (Table 4).


### Table 4 : Lists of crops and target weeds where multiple applications of bentazon are su22ested by univer s ity ae:ricultural exten sion documents.* Crops Weeds Corn 

### Kochia Sorghum Lambsquaters Pulses (lentils , soybeans , beans, pea, peanut, Redroot Pigweed etc.) Wild buckwheat Yell ow Nutsedge Canada thistle *Thi s li st is not exhausti ve. Compiled from Iowa State Un iversity Extens i on , South Dakota State Universi ty Extension , University ofGeorgia Extension, Penn State University Extension
. North Dakota State University Extension states that bentazon is more effective against kochia, lambsquarters , redroot pigweed, and wild buckwheat in dry beans when the chemical is applied in split treatments at lower concentrations, rather than a single application at the labeled rate (Zollinger et al., 2016). Furthermore, Zollinger et al. (2016) recommends up to 4 sequential app lications for greater control ofproblema tic broadleafweeds in soybeans. Sp lit treatments (7- 10 days apart) ofbentazon are also recommended for control of yellow nutsedge in soybean and corn (Penn State, University, 2009). There are likely other crops where bentazon is used in



### 6lower concentration, split treatments for particular weeds. Multiple applications ofbentazon may be needed to control particularly resilient weeds species and multiple germination events. Furthermore, limiting growers to one application for problematic weeds may encourage herbicide resistance.


### Herbicide Resistance Management
l'he EPA, Office of Pesticide Programs ' (OPP) , goal is to extend the useful life of chemica ls used for pest control by slowing the development ofresistance. The Agency announced at the Herbicide Resistance Summit II sponsored by the National Academy of Sciences (September I 0, 2014) , that it would take a more proactive role in developing regulatory approaches for managing resistant weeds. The Summit 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 of this problem and its impact on agricultural productivity.
Bentazon, Group 6 , inhibits photosynthesis at photosystem II site B. Bentazon is considered of moderate concern for herbicide resistance becaus e there is at least one Group 6 MOA resistant weeds species found in the U.S. and there are no bentazon resistant crops grown in the U.S. Therefore the registrant(s) should address elements 1 through 8 in Table 5. Table 5 lists the complete set of resistance management elements that can help slow the spread ofherbicide resistant weeds and Table 6 indicates which elements should be addressed based on mechanism ofaction (MOA) and use on herbicide resistant crops. Nine of the eleven items will be instructions placed on the label to provide information to the user (elements I through 7, I 0 and 11 where applicable) , and three ofthe e le ments will be instructions to the registrant (elements 8, 9 , and 11 where applicable). More information on herbicide resistance management is located in appendices I-III.


### Table 5. Elements of 

### resistance mana Ian

Element List Mechanism of Action (MOA) Group Number.
• This information is critical to allow the user to rotate between effective MOk's to reduce the buildup ofresistant pests. );;> Re istrant is res onsible for lacement on label. List seasonal and annual maximum number of applications and amounts. • This information is cr itical to allow the user to know how many 2 applications and amounts can be applied in order to develop an effective IPM plan for the season and the entire year. );:>- Re istrant is res onsible for lacement 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 3 HRAC proposed guidelines for herbicide labels.
• This is an educational opportunity to remind users to look for and follow a resistance management plan. 

## »- Re istrant is res onsible for lacement on label.

7User should scout before and after application. 

# • Reminding the user to scout can help insure that the proper pesticide is 4 applied based on the weed species and growth stage and determine if the 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 5 likely resistance users could proactively identify and attempt to control weeds in the early stages before they become widespread in their fields. );> Registrant is responsible for placement on label. User should report lack of performance 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 6 cases lack of performance could be an early 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. 7 

# • 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 of likely 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 8 available in a timely manner to users , consultants, extension, etc

. so that they are aware ofand proactively address the problem. 

## • Provide weed species, crop or site, state, and herbicide used

. );> Registrant is responsible for reporting. For sites of high concern provide growers with:

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

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

# • This is an educational opportunity to remind users ofthe importance of resistance management. );> Registrant is responsible for creating or providing educational materials. For combination products with multiple MOA, list which herbicide is controlling 10 which weed (a 3 way mixture may only have 1 effective MOA for some problem weeds). List minimum recommended rate if resistance is suspected.

8

# • Using a combination products with only one effective MOA can select for herbicide resistant weeds. 

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

# • Registrant is responsible for placing the list on label or otherwise providing the information. Any additional specific requirements (e.g. mandatory crop rotation, unique agronomic aspects, additional training , time limited registration, etc.). 

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

# • The elements may be on the label, the technical use agreement for the seed trait, or as a reporting requirement.**~** Registrant is responsible. Footnote: Mechanism ofAction Group number comes from the WSSA, definition ofresistance and likely resistance, PR Notice 2001

- 5 and BMP language are in Appendix 1

- 3. Resistance elements for fungicides and insecticides.


### T bl 6 H b' .d R

. 

## c f 

### C *

a e 

# . er 1c1 e es1stance ate2or1es o oncern Low Concern M ode rate Concern High Concern
• Any new herbicide with a new or

novel mechanism ofaction, or MOA's with no MOA's with a few resistant • Herbicide resistant crop(s) for resistance weed weed species in the U.S. that technology (conventionally species in the U.S. bred or GM) , or • MOA ' s with most resistant weeds

in U.S. 1. MOA on Label Elements I through 4 plus Elements I through 8) plus 2. List seasonal and 5. Definition of likely and 

### 9. Provide growers with: annual maximum confirmed resistance Resistance Management P lan, number of 6. Farmer should report Remedial Action Plan, applications and lack ofperformance to Educational materials on pounds registrant or its agent resistance management 3. Resistance 7. List confirmed resistant 10. For combination products with management species in separate multiple MOAs , list which language from table and list effective herbicide is controlling which PRN 2001-5 or or recommended rates weed and minimum BMPs for these weeds with recommended rate 

### 4

. Scout before and the table 11. Any additional specific after application 8. Registrant report new requirements (e.g. mandatory cases of likely and crop rotation , unique agronomic confirmed resistance to aspects , time limited EPA & users yearly registration, etc.). 

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



### 9Bentazon is at moderate risk ofresistance for weed species in the U.S., as there is at least one case ofherbicide resistance to this MOA in the United States (Heap, 2016). Regarding resistance to bentazon specifically, there are confirmed cases in Canada (Amaranthus species) and in Brazil (Sagittaria montevidensis), but no cases are documented in the United States (Heap, 2015). Considering that redroot pigweed (Amaranthus retrojlexus) has already developed resistance in Canada, and that university extension documents recommend split applications for controlling this species in dry beans , it is important not to limit the number ofapplications of bentazon in certain crops or situa tions where redroot pigweed, kochia, or lambsquarters is the target pest. Reducing the number ofapplications to only one per season cou ld negatively impact grower options

. Rice
Water holding time
Market research data indicate that bentazon is applied early postemergence-preflood and late postemergence pre-flood and post

-flood. Bentazon is used in drill-seeded rice culture and continuous flood cultures , and the chemical is applied to dry fields and flooded fields after rice has emerged. This herbicide must come into direct contact with plants; therefore , continuous flooded rice culture field s are sometimes partially drained in order to expose weeds to treatment. This application would likely occur while weeds are immature and the rice is tillering (several weeks before the draining ofthe field and subsequent harvest).
Weed control typically begins within days of flooding and continues until the canopy closes and weeds can no longer proliferate. Partial to full canopy closure can be expected in the final maturation stage (85-115 days after planting) , at which point the rice will begin to flower and ripen until harvest 130-165 days after planting (University of California, Davis, 1998). Water is typically drained 2-3 weeks prior to harvest to allow the field to dry enough to support harvest machinery. Considering that the underlying herbicide strategy for weed control is to kill weeds or stunt weed growth so that rice can gain a competitive height advantage (University of Florida, 2015), applications of bentazon will likely occur early to midseason (30-50 days pre-harvest). Label changes that would result in growers holding water in the fields for several days after bentazon application would likely have little impact on current management practices and weed control. In addition, any mitigation measures should avoid having growers drain and apply bentazon contemporaneously. Additional information on rice production practices can be found in U.S. EPA (2015).
Herbicide Resistant Management Concerns in Rice
Bentazon is a management tool used in rice to control ALS-resistant weeds. For example, the most problematic weeds in Arkansas rice include banyardgrass , red rice, and sedges (Cyperus spp.) (Tehranchian et al., 2 015 ). Mixing bentazon with propanil may limit the spread of ALSresistant sedges in rice fields as this mixture provides >96% control of ALS-resistant smallflower umbrella sed ge (Norsworthy, 2013). Sagittaria montevidensis (California arrowhead) is a



### I Ocommon weed species in rice production in the U.S. and there is confirmed resistance to bentazon in Brazil (Heap, 2015). 

### Droplet Size and Efficacy of Bentazon
The droplet size effects the efficacy and off site drift of a 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 of the most effective amount of active ingredient on plant foliage and reduction of off-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 of the 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 the interaction ofthe active ingredient with other chemicals in a tank mixture are some of the other factors that should be considered on selection ofoptimum droplet size. BEAD has limited information on the relationship ofdroplet size and efficacy for bentazon.
A study by Prokopf and Veverka (2003) concluded that " good coverage provided by fine droplet spectra is a prerequisite of high efficiency of the contact compound bentazon." Propkof and Veverka evaluated the efficacy ofbentazon using Galium aparine (stickywilly) and Chenopodium album (lambsquarters) using droplet spectra that ranged from 189 μm to 911 μm (fine to ultra course droplet size) 1 • The efficiency of Basagran 600 (600 g a.i./l) to control stickywilly dropped below 90% at 586**μman~** below 75% at 911 μm (ultra course)

. Control of lambsquarters dropped below 90% at 586 μm and below 61 % at 911 μm
. Control efficiency was highest (>95%) when droplet size was 183 μm (fine). Based on this study, there was no significant difference in efficacy for droplet sizes that ranged from 193 μm (fine) to 484 μm (very coarse), and droplets within this range would likely have similar control.
The American Society of Agricultural & Biological Engineers (ASABE) droplet volume median diameter (VMD) classification system differs slightly from the classifications used by Prokopf and Veverka. Coarse droplets , as defined by ASABE, range from 326 μm to 400 μm (Grisso and Hipkins , 2014). Based on Prokopfand Veverka's study, a label recommendation that limits droplet size in the ASABE coarse VMD range (326 μm to 400 μm) would likely not affect the efficacy of bentazon for ground applications.

1 American Society ofAgricultural & Biological Engineers Standard 11REFERENCES Basagran® Herbicide Product Label. Registration No. 7969-45-66330. Online Publication. Available at: http: //www.cdms.net/LDat/ld89N004.pdf. Accessed on October 30, 2015.
Extension Toxicology Network. 1993. Bentazone. Online Publication Available at: http: // pmep.cce.comell.edu/profiles/extoxnet/24d-captan/bentazon-ext.html. Accessed on October 27, 2015.
Owen, M. 2015. Iowa State University Extension. Herbicide Guide for Iowa Com and Soybean Production: Weed Management Update for 2016. Tuesday, February 23 , 2016. Available at: http://www.weeds.iastate.edu/mgmt/2015/WC94.pdf Grisso, R. D

. and Hipkins, P.A. (2014). Droplet Chart/Selection Guide. Available at: https: // pubs.ext.vt.edu/442/442-031 /442-031 pdf

. pdf. Accessed on November 16 , 2015. Heap, I. The International Survey ofHerbicide Resistant Weeds. Online. Internet. Tuesday, November 10, 2015. Available at: www.weedscience.org
HRAC

. 2015. Herbicide Resistance Management, Proposed HRAC Stewardship Guidelines for Herbicide Labels. Accessed online on September 24, 2015 at http: //www.hracglobal.com/pages/hracstewardshipguidelinesforherbicidelabels.aspx
Johnson, P .O, Deneke, D. , Vos, D. , Alms, J. , Wrage, L.J. 2015. South Dakota State University. 2015 Weed Control: Sorghum. Tuesday, February 23, 2016. Available: http s://igrow.org/up/reso urces /03-3013

-2015.pdf
Market Research Data (M RD ). Various years. Data collected and s old by a private market research firm

. Data collected on pesticide u se for about 60 crops by annual surveys of agricultural users in the continental United States. Survey methodology provides statistically valid results , typically at the state level.
Odero , D .C. and Rainbolt , C. , 2014. Weed Management in Rice. University of Florida IFAS Extension. Available: http s://edis .if as. ufl.edu/pdffiles/WG/WGOO 100.pdf. Accessed November 11 , 2015.
Penn State University. 2015. The Agronomy Guide: 2015-2016. " Weed control reccomendations for grain sorghum, forage sorghum , sorghum x sudan hybrids. Available at: http: //extension.psu.edu/agronomy-guide /pm/tables/table2-3-1. Accessed on February 2 Prokopf , M

. and K. Veverka. 2003. Influence of droplet spectra on the efficiency of contact and systemic herbicides

. Plant Soil and Environment 49 (2): 75-80. Available at http://www.agriculturejouma ls.cz/publicFiles/52830.pdf. Accessed on November 2, 2015.

12Norsworthy, J. K., Riar, D.S. , & Scott, R. C. (2013). Control options for ALS-resistant smallflower umbrella sedge in Arkansas rice. BR Wells Arkansas Rice Research Studies. University of Arkansas Agricultural Experiment Station Research series, 617, 222-226. 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. Bur gos, W.W. Witt, and M. Barrett. 2012. Reducing the Risks of Herbicide Resistance: Best Management Practices and Recommendations. Weed Science 20 12 Special Issue: 31-62. Available online at: http://www.wssajournals.org/doi/pdf/l 

### O. l 614/WS-D-11-00155. l
Tehranchian, P. , Riar, D .S., Norsworthy , J. K. , Nandula, V. , McElroy, S., Chen, S., & Scott, R. C. (2015). ALS

-Resistant Smallflower Umbrella Sedge (Cyperus difformis) in Arkansas Rice: Physiological and Molecular Basis of Resistance. Weed Science.
Texas Rice Production Guidelines. 2014. Texas A& M Agri life Extension. Texas A&M University. Online Publication. Available at: http://extentopubs.tamu.edu/pdf/2014 Rice Production Guidelines.pdf. Accessed on October 30, 2015. University of Arkansas. 2013. Arkansas Rice Production Handbook. University of Arkansas Division of Agriculture. Available at: http:/ /www. uaex.edu/publications/pdf /mp192/mp192.pdf. Accessed on November 11, 2015. University of California, Davis. 1998. Crop Profile for Rice in California. Online. Available: http: //www .ipmcenters .org/cropprofiles/docs/carice.pdf. Acces sed on November 12, 2015. University of Georgia. 2009. 2009 Peanut Update. Accessed on February 23 , 2016 at: http: //www.caes.uga.edu/commodities/fieldcrops/peanuts /2009peanutupdate /documents/Pe anut_ Weed.pdf
U.S. EPA. 1985

. Chemical fact sheet for bentazon and sodium bentazon. Fact sheet no. 64. Office of Pesticide Programs

. Washington, DC

. U.S. Environmental Protection Agency (EPA). 2009

-2013. Proprietary Data.
U.S. Environmental Protection Agency (EPA). 2015. BEAD Response to the Dow AgroSciences Comments on Rice Production Practices and Use of Cyhalofop-butyl for Weed Control in Rice Production

. Office ofPesticide Programs, Biological and Economic Analysis Division Zollinger, R.K., Christoffers, M. , Dalley, C. , Endres , G. , Gramig , G. , Howatt, K. , Jenks , B ., Lym, R., Ostlie, M., Peters, T. , Robinson, A. , Thostenson, A. , and Valenti, H. 2016. North Dakota Weed Control Guide. Fargo, ND, North Dakota State University Extension Service, Publication W-253. Available at: https://www

.ag.ndsu.edu/weeds/weed

- control-guides/ndweed-control-guide-1

13

### APPENDIX I. Guidance for Pesticide Registrants on Pesticide Resistance Management Labeling
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 of action group number) herbicide. Any weed population may contain or develop plants naturally resistant to (name of product) 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 of action but are specific for individual chemica ls , 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, for example:
b. " For resistance management, please note that (name of product) is both a Group (mode ofaction group number) and a Group (mode ofaction group number) herbicide. Any weed population may contain plants naturally resistant to Group (mode of action 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 use 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 ;

14precision 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 ear ly 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 of the
same species. Ifresistance 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 of resistant 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, di scontinue use of this 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). "

15APPENDIX II. Definition of Resistance and Likely Resistance According to the Weed Science Society of America " Herbicide resistance is the inherited ability of a plant to survive and reproduce following exposure to a dose ofherbicide normally lethal to the wild type. In a plant, resistance may be naturally occurring or induced by such techniques as genetic engineering or se lection 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 genet ic manipulation to make the plant tolerant; it is naturally tolerant. " (http: // weedscience.org/documents/resistancecriterion.pdO.

Indicators of likely herbicide resistance (called possible resistance in Norsworthy et al 2012, Page 39) include (1) failure to control a weed species normally controlled by the herbicide at the do se applied, especially if control is achieved on adjacent weeds; (2) a spreading patch of noncontrolled plants of a particular weed species ; and (3) surviving plants mixed with controlled individuals of the same species.

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### APPENDIX III. Best Management Practices for Herbicide Resistant Weeds Crop Selection and Cultural Practices : I

. Understand the biology ofthe weeds present. 2. Use a diversified approach toward weed management focused on preventing weed seed production and reducing the number of weed seeds in the so il 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 harvest and post-harvest to prevent a buildup of the weed seed-bank. 8. Prevent field-to-field and within-field movement of weed seed or vegetative propagules. 9. Thoroughly clean plant residues from equipment before leaving fields. 10. Prevent an influx ofweeds into the field by managing field borders. 11. Fields should be scouted before 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 escapes. 14. Avoid outcrossing to weedy relatives, 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 mechani sm 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 identified through scouting and field history. 3. Difficult to control weeds may require sequential applications ofherbicides with alternative mechanisms of action. 4. Fields with difficult to control weeds should be rotated to crops that allow the use of herbicides with alternative mechanisms of action

. 5. Apply full rates ofthis herbicide for the most 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 herbicide " or any herbicide with the same mechanism of action within a single growing season unless mixed with another mechanism of action herbicide with overlapping spectrum for the difficult to control weeds. 7. Report any incidence ofnon-performance of this product against a particular weed species to the representative (list contact information here)

. 

### Footnote: Most items are taken from the Herbicide Resistance Action Committee I Weed Science Society of America li st of Be st Management Practices.

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