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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D

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.. 20460 

## MAR 0

## 32015 OFFICE OF PREVENTION , PESTICIDES AND TOXIC SUBSTANCES MEMORANDUM SUBJECT:

FROM:

THRU:

TO: 

### Benefit Assessment on the Use ofQuinclorac in Rice Production (PC 128974) Sunil Ratnayake, Biologist Biological Analysis Branch

# ~**V\1~** Jihad Alsadek, Economist

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# ~ Science Information and Analysis Branch T J Wyatt, Economist 

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### ...lDtS' Biological and Economic Analysis Divi on (7503C)

# ~ Arnet Jones, Chief Biological Analysis Br 

### Diann Sims,

# Chief~ Science Information and Analysis Branch Timothy Kiely, Chief 

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# j . C Biological and Economic Analysis Division (750 Margaret Hathaway, Chemical Review Manager Risk Management and Implementation Branch RMB II Pesticide Re-evaluation Division (7503 P) PEERREVIEW PANEL: 

### February 11, 2015 SUMMARY 

### As part ofthe re-evaluation process ofregistration ofquinclorac, this document contains an assessment ofbenefits ofthe use ofquinclorac inrice production. Quinclorac is a selective and systemic herbicide applied for the control ofgrasses and certain broadleaf weeds in rice production.Jt is widely used for the control ofpropanil resistant barnyardgrass biotypes. Qpinclorac can be applied eitherpre-emergence, postPage 1emergence, or as a late-season salvage treatmentto control grasses and some broadleaf weeds found in the rice production. Clomazone, pendimethalin, and thiobencarb are available alternative pre-emergence treatments for control ofbamyardgrass. Similarto quinclorac, these herbicides provide residual activity. Bispyribac-sodium, cyhalofopbutyl, fenoxaprop, propanil, pendimethalin, penoxsulam, clomazone, and thiobencarb are herbicides that can be used as post-emergence treatments. Quinclorac provides a wide application window and canbe applied as pre-emergence, early post-emergence or late-season salvage treatment in drill seeded rice

_ and as an early post-emergence foliar treatment or late-season salvage treatment in water seeded rice. Despite the activity against grassy weed species, quinclorac will generally not cause herbicide injury to the rice crop. Furthermore, according to the classification of mechanism ofaction ofherbicides, quinclorac belongs to the mechanism ofaction Group 4 (WSSA, Undated 2). Itis often tank-mixed with other herbicides such as clomazone (Group 13), pendimethalin (Group 3) propanil (Group 7), and thiobencarb (Group 8) to minimize the development ofherbicide resistance in weed species found in rice production. In addition, the weed spectrum controlled by the individual herbicide varies considerably and bytank-mixing ofthese herbicides, compatible herbicides can be applied in a single application to minimize the cost ofherbicide application and achieve a broader spectrum ofweed control. Usage 

### Information on Quinclorac Onthe basis ofavailable proprietary data, the highest agricultural usage ofquinclorac is for weed control in rice production. Nationally, about 300 thousand pounds active ingredient (lbs. a.i.) ofquinclorac is applied annually onrice with an average of30 percent crop treated (BEAD, 2012). This usage onrice was mainly inArkansas, Louisiana, Mississippi, Missouri, and Texas. The p.igh proportion ofrice treated with quinclorac suggests that itprovides benefits to rice growers. Quinclorac can be applied either pre-emergence, post-emergence, or as a late-season salvage treatment to control grasses and some broadleafweeds that escape previous applications or emerge later in the season. Also, quinclorac is widely used for the control ofpropanil resistant bamyardgrass biotypes found inthe rice production (WSSA, Undated) In the United States, rice is grown in Arkansas, California, Louisiana, Mississippi, Missouri, and Texas (USDA ERS, 2013). Arkansas, with over 42% ofthe nation's total rice production, produces more rice than any other state. In 2013, about 1.1 million acres ofrice were harvested in Arkansas, with total production of81 million cwt (USDA ERS, 2014). Between 2008 and 2012, about 45 percent ofthe rice acreage in Arkansas was treated with quinclorac (Proprietary data, 2009-2013). About 60 percent ofthe acreage is treated by air eventhough aerial applications are proscribed in some areas around Crowley's Ridge in Poinsett and Craighead Counties to prevent damage to other crops from potential spray drift. Usage ofquinclorac in Californiais limited and according to proprietary data (2009- 2013), less than tenpercent ofthe rice area was treated for bamyardgrass control.
Page2Given the importance ofrice production and the extent ofusage ofquinclorac inthe state, Arkansas is the primary focus ofthis document, butthe results are indicative ofthe role quinclorac plays throughout rice production in the region. Use 

### ofQuinclorac in Rice Production Quinclorac is a selective and systemic herbicide applied for the control ofgrasses and certain broadleafweeds in rice production. Quinclorac can be applied

## as a preemergence, or early post emergence treatment in drill seeded rice and post-emergence foliar treatment on water seeded rice. Also, quinclorac can be applied as a late-season salvage treatment in rice production systems (Bennett, 2003). In Arkansas, most of quinclorac usage is as post-emergence treatments (proprietary data, 2009-2013). According to proprietary survey data, rice growers primarilytarget barnyardgrass with the use ofquinclorac. Weed control experts in Arkansas estimate 70% yield reduction of rice can occur due to the heavy, season long weedinterference ofbarnyardgrass (Univ. of Arkansas, 2013). The problem is exacerbated because biotypes ofweeds withresistance to several herbicides, including clomazone, propanil, and quinclorac, have been found in Arkansas (WSSA, Undated). Currently, !hesethree herbicides are the most widely used herbicides, in terms ofarea treated, for the control ofbarnyard grass in the rice production as shown in Table 1 (Proprietary Data, 2009-2013). T bl 

### 1 H b" "d

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### b e use or d tr 

### l . th arnyar Lgrass con o IJl d f e nee pro uc 

### wn . Average area treated for Average cost per acre 2 Chemical barnyardgrass (2009-2013) ($) Quinclorac 749,000 18.10 Bispyribac-sodium 68,000 27.40 Clomazone 1,197,000 11.30 Cyhalofop-butyl 144,000 29.50 Fenoxaprop 92,000 24.70 Pendimethalin 89,000 6.60 Penoxsulam 39,000 19.40 Propanil 608,000 16.30 Thiobencarb 92,000 13.40 Source: Proprietary data, 2009-2013. 1 Alabama, Arkansas, Louisiana, Mississippi, and Missouri. 2 Average chemical cost per acre for a treatment targeting barnyardgrass across acres treated with varying application rates. 

### Available Alternatives Weed management decisions in rice are made based onthe situations in individual fields. 

### Itrequires a good knowledge ofthe types ofweeds in the field, efficacy ofherbicides on different weeds, herbicide application timing, application rates, and residual effects. Moreover, herbicide selection must consider potential injury to the rice, especially herbicides for control ofgrass weed species. Resistance managementpractices, such as Page 3

### tilling, crop rotation, and the use ofherbicides with different modes ofaction are important to minimize the development ofweed re.sistance in rice production. Many registered herbicides are available as alternatives for the weed control in rice production. A list ofthese herbicides that can be used at different application timings in rice production is given in Table 2. In addition to controlling grass weed species, including barnyardgrass, these herbicides controls certain broad leafweed species found inthe rice production. As shown in Table 2, spectrum ofweeds controlled by the individual herbicide varies and depending on the weed spectrum found in the field, effective herbicides on different weeds canbetank-mixed and applied in a single applicationto minimize the development ofweed resistance, cost ofherbicide application, and to achieve a broader spectrum ofweed control. Clomazone is the most commonly applied pre-emergence treatment and it is relatively inexpensive than other herbicides (Table 1). Clomazone provides residual activity and it can also be applied as pre and post-emergence treatments. However, it is rarely applied as post-emergence treatment for weed control in rice production. Only one application of clomazone per year is allowed under the label. According to proprietary data, rice growers rarely use pendimethalin and thiobencarb for the grass weed control including, barnyardgrass despite the fact that they are relatively inexpensive (Table 1 ). Also, both of these herbicides have relatively narrow windows for pre-emergence applications to avoid injury to the rice. Early post-emergence applications ofthese chemicals are often tankmixed with other compatible herbicides, including quinclorac, to provide broader spectrum ofweed control including broadleafweeds (Univ. ofArkansas, 2013). Quinclorac is commonly applied as post-emergence treatments for weed control in rice production. Cyhalofop-butyl, fenoxaprop, bispyribac-sodium, propanil, pendimethalin, penoxsulam, clomazone, and thiobencarb also can be used as post-emergence treatments for weed control in rice production. Propanil and quinclorac are extensively used for weed control in rice production (Table 1). Due to the extensive use ofthese herbicides, certain biotypes ofbarnyardgrass have developed resistance to both ofthese herbicides (Univ. ofArkansas, 2013). Bispyribac-sodium and cyhalofop-butyl can also be used as late-season salvage treatments. However, proprietary data indicate that growers rarely use these herbicides and they are more expensive thanthe quinclorac (Table 1 ). Bispyribacsodium does not provide residual weed control. However, bispyribac-sodium and penoxsulam more commonly used for broadleafweed control and they are effective on controlling bamyardgrass found in the rice production. In addition, cyhalofop-butyl and fenoxaprop are effective for bamyardgrass control, including biotypes resistant to propanil and quinclorac. However, they cannotbe mixed with some common herbicides used for broadleafweed control (Univ. ofArkansas, 2013).

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### Table 2.**H~rbicides** 

### Used as Alternatives to Quinclorac for Weed Control in Rice Production1•
Stage of Remarks Application Herbicide

Clomazone is a pre-emergence herbicide with residual activity. It is applied for weed control in dry seeded rice, 14 days before or7 days after the drill seeding ofrice activity

. Clomazone Clomazone controls annual grasses and some broadleafweeds

. Major grassy weeds controlled are bamyardgrass, braadleafsignalgrass, crabgrass, panicum species, and sprangletop

. Majorbroadleafweeds controlled are spurred anoda, velvetleaf, ragweed, lambs quarter. Clomazone does not have a late post-emergence activity and it can be applied only once per season. Pre-emergence

Pendimethalin can be applied as pre-emergence or early post-emergence treatments. It has Pendimethalin a long residual activity

. In additionto bamyardgrass, it is effective on sandbur, goosegrass, Post-emergence witchgrass, crabgrass,junglerice, seedlingjohnsongrass, crowfootgrass, sprangletop, broadleafsignalgrass, and panicl!ffi species. Pendimethalin is applied only afterrainfall or shallow irrigation for the germination ofrice seeds.
Thiobencarb Thiobencarb is applied as a delayed pre emergence treatment. It provides "excellent control ofsprangletop, bamyardgrass and several aquatic weeds. Thiobencarb provides residual activity. Applications ofthis herbicide are made I to 5 days before rice emergence or about 5 to 9 days after planting, Clomazone can be applied as an early post-emergence treatment at I to 2 leafstage ofrice. Clomazone It controls annual grasses and some broadleafweeds. Major grassy weeds controlled are bamyardgrass, broadleafsignalgrass, crabgrass, panicum species, and sprangletop

. Major broadleafweeds controlled are spurred anoda, velvetleaf, ragweed, lambs quarter. It can be tank mixed with quinclorac. Clomazone does not have a late post-emergence activity
Fenoxaprop can be applied as a post-emergence treatment to control annual grasses in rice Fenoxaprop production

. Foliar coverage ofemerged grasses is important. Controls bamyardgrass, broadleafsignalgrass, fall panicum, seedlingjohnsongrass, and sprangletop

. Irrigated water must be drained from the field priorto fenoxaprop application to expose the weeds

. Fenoxaprop is not as effective as other chemicals on broadleafspecies.
Propanil is applied as a post-emergence herbicide to control grassy weeds and some Post-emergence broadleafweeds in rice production

. Propanil is effective in controlling barnyard grass. Due Propani! to the extensive use, biotypes ofbamyardgrass have develop resistance to this herbicide. In addition to bamyardgrass propanil controls crabgrass, broadleafsignalgrass, goosegrass, panicum species, foxtail species, and broadleafweed species such as woolly croton, curly dock, hemp sesbania, and redrootpigweeds. Propanil does nothave residual activity and to broaden the weed control spectrum and efficacy, propanil can betank mixed with quinclorac, pendimethalin, clomazone and thiobencarb.

Page 5Stage of Remarks Application Herbicide
Pendimethalin can be applied as an early post-emergence treatment. It has a long residual activity

. Pendimethalin can be tank mixed with herbicides such as propanil, quinclorac, Pendimethalin thiobencarb and clomazone to brpaden the spectrum ofweed control. In addition to bamyardgrass, itprovides a good control ofgrass weeds such as field sandbur, goosegrass, witchgrass, crabgrass,junglerice, seedlingjohnsongrass, crowfootgrass, sprangletop, broadleafsignalgrass, and panicum species. To have a better weed control application s of this herbicide should be made at 1-3 leafstage ofthe bamyardgrass.

Thiobencarb can be applied as a post-emergence treatment to control grassy and some Thiobencarb broadleafweeds

. The post-flood applications ofthiobencarb control weed species such as bamyardgrass,junglerice, spamgletop, duck salad, and redstem

. Ifneeded, thiobencarb can be tank mixed with other herbicides such as clomawne, pendimethalin, propanil, and quinclorac to increase the efficaoy andrange ofweed control.

Cyhalofop-butyl Cyhalofop-butyl is a broad spectrum grass herbicide which controls tough grasses such as propani! and quinclorac resistance bamyardgrass, sprangletop, broadleafsignal grass, fall panicurn, knot grass, andjungle rice. Itoffers a broad application window and can be applied from 1-2 leafstage to 60 days before harvest.
Bispyribac-sodium has a broad application window and can be applied as pre-flood, postBispyribac-sodium flood, or late post-treatments
. It provides a good control ofbamyardgrass and rice flatsedge

. In addition, this herbicide controlsjohnsongrass, duck salad, dayflower, Indian jointvetch, Pennsylvania smartweed, and northernjointvetch

. This herbicide does not have residual activity. To increase the spectrum ofweed control, bispyribac-sodium can be tank mixed with thiobencarb, 2, 4 -D, clomawne, and pendimethalin.

Penoxsulam is applied as a post-emergence treatment on rice from seedling emergence (drill seeded rice) to 60 days before harvest. Penoxsulam controls broadleafand certain Post-emergence grass weeds in rice production, including barnyardgrass,junglerice

. Eclipta, hemp Penoxsulam sesbania, rice flatsedge, cocklebur, duck salad, pigweed, and smartweed are the otherweed species controlled by penoxsulam. To increase the weed control spectrum this herbicide can be tank mixed with propanil, quinclorac, pendimethalin and other compatible herbicides

.

Bispyribac-sodium Bispyribac-sodium can be applied as a mid-season salvage treatment. It is effective in controlling propanil resistant bamyardgrass. In addition, it controls rice flatsedge. Later season Johnsongrass, duck salad, dayflower, Indianjointvetch, Pennsylvania smartweed, and northernjointvetch. To increase the weed control spectrum bispyribac-sodium can be tank (mid-season) mixed with herbicides such as thiobencarb, 2, 4-D, clomawne, and pendimethalin

salvage treatment Cyhalofop-butyl Cyhalofop-butyl offers a broad application window and itcan be applied from 1-2 leaf stage ofrice to 60 days before harvest. It is a broad spectrum grass herbicide and effective against propanil and quinclorac resistant bamyardgrass biotypes

. Cyhalofop-butyl does not have a residual activity.

Page6Stage of Remarks Application Herbicide Quinclorac is applied for the control ofgrassy weeds, and certain broadleafweeds

.. Rice Pre-emergence, crop has an excellent tolerance to quinclorac and does nottypically damage the rice crop. Quinclorac provides a long term residual activity and it is applied as pre emergence, post Post emergence, or as a mid-season salvage treatment. It can betank mixed with pendimethalin, emergence, and Quinclorac propanil, clomazone orthiobencarb

. Itis effective in controlling grassy weeds such as

Mid-season broadleafsignal grass, crabgrass and bamyardgrass, including some propanil resistance

salvage bamyardgrass biotypes susceptible to quinclorac. Also, quinclorac controls some broadleaf weeds such as hempsesbania,jointvetch, eclipta, and momingglory

. In addition, it provides late post emergence activity. Quinclorachas a wider application window, broad spectrum ofweed control, and it is effective on grassy weeds including propanil-resistant bamyardgrass biotypes which has not developed resistance to quinclorac

. Source: (CDMS, Undated); Umv

. ofArkansas, 2013. 1For more information on herbicide application timing, rice production systems, and comparison ofefficacy ofthe listed herbicides, please refer to Univ. ofArkansas Rice Production Handbook, 2013. Available at: : /www.uaex.edu/ ubhcations/ d£ m I m I 2. df Benefits ofQuinclorac Quinclorac provipes excellent control ofbarnyardgrass, although some biotypes have developed resistance. It also provides control ofst?veral other important weed species, including broadleafsignalgrass, crabgrass, morningglory, and hemp sesbania (Univ. of Arkansas, 2013). Rice has an excellent herbicide tolerance for quinclorac (quinclorac does not cause herbicide injuries onrice crop). Also, quinclorac has a broad application window and it canbe applied as a pre orpost-emergence treatment in drill seeded rice andpost emergence treatment on water seeded rice. Furthermore, depending on the weed situation, quinclorac can be applied as a mid-season salvage treatmentto control grassy weeds which escaped early season herbicide treatments. 

### In addition to grass weeds, quinclorac controls certain broadleafweed such as·eclipta, Northernjointvetch, pitted morningglory, and palmleafmorningglory (Univ. ofArkansas, 2013). Quinclorac belongs to HRAC mechanism ofaction Group 4 and it is often tank-mixed or rotated with other herbicides such as clomazone (Group 13), pendimethalin (Group 3) propanil (Group 7), and thiobencarb (Group 8) to broaden the spectrum ofweed control and minimize the development ofherbicide resistance in weeds found in rice production. REFERENCES: BEAD (Biological and Economic Analysis Division). 2012. Screening Level Estimates of Agricultural Uses ofQuinclorac. Bennett, D. 2003. Facetplays big role inArkansas rice. http://deltafarmpress.com/mag/farming facet plays big/

. Accessed on Jan. 30, 2015. Crop Data Management Systems, Inc. (CDMS). Undated.**http:/ www.cdms.net/l~belsmsds** **lmdefault.aspx .**  Accessed on Feb, 2, 2015. Proprietary Data, EPA. 2009 to 2013.
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### University ofArkansas. 2013. Arkansas Rice Production Handbook. University of Arkansas Division ofAgriculture, Cooperative Extension. PublicationNo. MP 192. Online Publication. Available at: http://www.uaex.edu/publications/pdf!MP192/MP192.pdf

. Accessed on Jan. 15, 2015. USDA ERS. 2014. Rice Year Book. Economic Research Service, U.S. Department of Agriculture. Available at http://www.ers.usda.gov/data-products/rice-vearbook2014.aspx

. Accessed onJan. 29, 2015. Weed Science Society ofAmerica (WSSA). (Undated). Multiple resistant barnyardgrass 

### (Echinochloa crus-galli) resistance to herbicide groups C2/7, and 0/4 USA: Arkansas. http://www.weedscience.org/Case/Case.asp?resultsiD= 1188

. Accessed on January 30, 2015. Weed Science Society ofAmerica (WSSA) (Undated). Summary ofHerbicide Mechanism ofAction According to the Weed Science Society ofAmerica. Available at: http:/ /wssa.net/wp-content/uploads/WSSA-Mechanism-ofAction

. pdf

. Accessed on February 23, 2015.

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