Page **1** ofS **UNITED STA** 

**TES ENVIRONMENTAL**  **PROT E**  **C TION**  **AGEN C**  **Y** WA SHINGTO N , D. C

. 20460 

## DE **C 0**  **6 2013** 

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION
**MEMORANDUM**
**SUBJECT: FROM:** 

**TH R**  **U:**

**T O**  **:** B EAD Chemical Profile for Registration Review: Dithiopy r (128994) Sunil Ratnayake, Biologi st /\ 

# Jr""\ Biological Analysis Branch (_ \ Cy nthia Doucoure, Environmental Protection Specialist 

### {j

_ - Science Information and Analysis Branch Stephen Smearman , Econo m i st Economic Analysi s Branch Biological and Economic An alys is Division (7503P) Arnet Jones, Chief 

# /J ...+.. 

### 'i Biological Analysis Branch 

# Ylf Diann Sims, Chief 

# 4

. · " Science Information and Analysis Branch Tim o thy Kiely , Chief L Economic Analysis Branch \ J ) \ Biological and Eco nomic Analysis Division ( 3P) V. Dutch, Chemic a

l Review Manager Risk Management and Implementation Branch 4 Pesticide Re
- evaluation Division (7508P)


### Product **Review Panel**  **date: July**  **17, 2013** Page 2 of5

**INTRODUCTION** The purpose of this document is to convey usage information and a broad overview of the pest management roles of pesticides that are beginning to undergo registration review. The anticipated audience consists of the team of EPA staff currently evaluating the re gi s tration status of dithiopy

r, and eventually th

e general public. This document builds upon the data already provided in the Label Use Information System (LUIS) reports and the Screening Le vel Usage Analysis (SLUA) that BEAD provides to the Registration Review teams. The document is based on information and data available to BEAD as ofNovember 201 3
. Dithiopy r was first registered in the U.S. in 1991 as a conventional herbicide (USEPA, 1 991 )
. Dithiopy r herbicide belongs to the pyridines group of herbicides (Weedscience.org, 2013). It is applied as a pre and post- emergence herbicidefor the co n t rol of grasses and small seeded broad leaf weeds. This herbicide is not registered for agricultural uses and it is predominantly used for the control of grass weed species in no n-agricultural sites described below. According to the Weed Science Society of America (WSSA) mechanism of action classificatio n, dithiopyr belongs to the group 3 herbicides. The mechanism of action of this group of herbicides is inhibition of assembly of microtubules in the process of cell division of suscep t i ble weeds (Weedscience.org, 2013).
**HISTORY OF**  **BEAD ASSESSMENTS**  **FOR DITHIOPYR**  A search of the BEAD Official Records data base did not find any relevant assessments for dithiopyr. **COMMON FORM**  **U L** **A T** **I ONS**  **AND APPLICATION**  **METHODS** Dithiopy r is formulated as emulsifiabl e , suspension, and soluble concentrates, water soluble pouches, granules, and liqui d s ready
- to - use. Dithiopy r is applied as a ground broadcast application using rotary- or drop
- ty pe spreader s , conventional liquid applicati o n equipment including hand
- operated sprayers (backpack, tank or pump -up type ) , and hose
- end sprayers. Dithiopy r is also used as a crack and crevice treatment using a foam applicator.
**USE SITES**  Agricultural Use Sites Dithiopy r is not registered for use on agricultural crops. No n- Agricultural Use Sites Dithiopy r is lab e l ed for use on landscap e , field, and container grown ornamentals l o cated in ornamental garden s , park s , golf courses, and residential areas; on no nbearing fruit and nut trees (nonfood producing trees); on turf sites (resident i al and institutional l awns, athletic f i eld s,Page 3 of5

commercial sod farms, and golf course fairways, and roughs); and uncultivated nonagricultural areas including roadsides, utility right
- o f
-ways, railway s , and industrial areas.
PROFESSIONAL TURF AND ORNAMENTAL USAGE IN THE U.S. Dithiopy r is used primari l y in th

e professional turf and ornamental markets as a pr e-emergence herbicide in the U.S., as reported in private market research studies for the ye ars 2004, 2006, and 2011. When i t comes to di t hiopy r sales by brand, Dimension®, is one of the top herbicides used on golf courses and by lawn care operators and is g aining ground in other sectors. Total use of Dith i opyr in terms of pounds a.i. applied, has reportedly increased by nearly 200% since 2004 as shown in Table 1
. Acre treatments of the brand, Dimension®, have also increased by 17% since 2004. The predominant use in the professional turf and ornamental market is on golf c ou rses and lawns. However, the most recent ye ars of data show use increasing in terms of pounds ai applied and in acre treatments for areas such as horticu ltural nurseries, institutional turf, and landscape co n t ractors as shown in Tables 1 

### & 2.
Tabl e 1
. Dith

i opyr Pounds A.I. Appl ied, 2004, 2006, and 2011 Sector Pounds 

### A.l. Applied: Pr e - em e rgence (Th o usand Lb A.l. ) 2004 2006 201l Golf Courses 48 66 95 Lawn Care Operators ( LCOs ) 102 97 223 Horticultural Nurseries N/A N/A 42 Insti t utional Turf N/A 

## NIA 46 Landscape Contractors N/A 15 38 Turf Farms N/A 

## NIA 5 Total 150 178 

### 449 Source: EPA Propnetary Data, USA, 2005,2007, and 2012
Table 2
. Product ( Dimension® ) Acre Treatments, 2004, 2006, and 20 1 1 Sect or Product (D i me nsion® ) Acre T

r e a tme n t s : Pre - emergence Thousand Acres ) 2004 2006 2 0 11 Golf Courses 222 198 1 68 Lawn Care Operators ( LCOs ) 502 382 369 Hortic ul tural Nurseries N/A N/A 118 Institutional Turf 

## NIA 56 102 L andscape Contractors 

## NIA 55 80 Turf Farms 7 24 19 Total 731 715 856 Source: EPA Proprietary, 

### 2005, 2007, and 

### 2012Page 4 of5

BEAD also found one ye ar of data in USDA NASS (2009) for dithiopy r, which shows that 100 pounds of dithiopy

r were applied on nursery and floriculture at an average appl ication rate of 0.472 lb/acre. This application rate is only slightly lower than the dithiopyr maximum single application rate of 0.498 lb/acre on ornamental lawns, turf, and landscape ornamentals as found on dithiopyr labels.
**BIOLOGICAL ASPECTS**  **RELEVANT TO**  **DITIDOPYR** Dithiopy r is an herbicide appl ied for the control of annual grasses and broadleaf weeds in nonagricultural sites. D i

t hiopyr is effective on controlling major grass weed species such as bar ley 

### (Hordeum spp.) l arge crabgrass 

### (Digitaria sanguinalis),smooth crabgrass 

### (Digitaria ischaemum ), sout hern crabgrass 

### (Digitaria ciliaris ) , barnyardgrass 

### (Echinochloa crus- galli), goosegrass 

### ( Elusine indica), and foxtails 

### (Setaria spp.) (Dimension® EC. Product Label. 2003). In addition, dithiopy r is used to control annual broa dl eaf species such as carpet weed 

### (Mollugo verticillata ), Chickweed 

### (Stellaria spp.) henbit 

### (Lamium spp.) prostrate knotweed 

### (Polygonum aviculare ), redroot pigweed 

### (A maranthus retrojlexus), and spurge 

### (Euphorbia) species. According to the Weed Science Society of America (WSSA) mechanism of action classification, dithiopy r belongs to the group 3 herbicides and presence of bioty pes of 6 weed species resistant to group 3 herbicides has been reported in the United States (Weedscience.org, 2013). These weed species are Palmer amaranth 

### (Amaranthus palmeri ) , wild oats 

### (

Avenafatua

), goosegrass 

### (Eleusine indica), rigid ryegrass 

### (Lolium rigidum), annual bluegrass 

### (Poa annua), green foxtail 

### (Setaria viridis), and Johnsongrass 

### (S orghum halepense). Although the presence of bioty pes of weeds with resistance to dithiopyr is reported, a reduction of usage is not observe d
. This may be due to the effectiveness of this herbicide on controlling major grass weeds found in many non - agricultural site s . Among the major grass weeds, dithiopyr controls several crabgrass species (large crabgrass, smooth crabgrass, southern crabgrass). Pr e -emergence as well as post - emergence applications of dithiopy r are recommended and a better crabgrass control can be achieved by post - emergence appl ications of this herbicide during the early growth stage of crabgrass (before tillering). Postemergence applications at early growth stages can provide 2 to 8 weeks of additional control of crabgrass found in the fields. According to the product label, applications of d i thiopy r can be made as a single application or sequential application in the spring, summer, or fall. However, no t more than 1.5 lb ai/ac should be applied per ye ar using split or sequential applications (Dimen si on® EC, Product lab el , 2003).

**ROLE OF**  **DITIDOPYR IN**  **PEST MANAGEMENT**  Dithiopy r is used primarily for preemergence control of annual grasses and broadleaf weeds in established lawns, golf courses, ornamental turf, commercial sod farms, non - croplands, industrial sites, field grown or container grown nursery ornamentals. The predominant use of dithiopy r inP age 5 of5

the professional turf an d orn a me n tal market is on golf courses and lawns. However, the most r ece nt ye ars of data show use increasing in te r m s of pounds ai appl i ed and in acre treatments for areas such as horti c ultura l nurserie s , in s t itutional tur f

, and landscape contractors. Based on th e available data, it ap pe ar

s that use of dithiop yr on th ese s i tes has been in cr ea s in g overall from 20 04 to 2011, whi

ch i s an indication of the rel a tive importance of dithi

opyr to the professional turf and ornamental market in controlling weeds. The role of dithiop yr in pest management in uncultivated non - agricultural site s , however, i s not apparent due to the l ack of avai lable d a ta.
**INFORM A** **TION THAT**  **MAY BE**  **USEFUL FOR**  **B EAD'S**  **FUTURE WORK**  **O N**  **DITHIOPYR** O btaining additional in f o rmation on the current use of dithiopy r in un c u ltivat

ed non - agricultural and industrial sites would improve future BEAD assessments and may b e r equired as part of the re g istration review of t hi s p es t ic ide. Information n e e ded regarding the curre nt use of dithiopyr on a ll s ites include s the annual pounds of a.i. applied in the U.S., the number of a c r e treatment s , ty pical application rates (s i n gl e and yearly) , and the number of app l i cations per year. **REFERENCES** Dimension® EC. Product Label. 2003. Dow AgroSciences LLC
. Indianap o l i s, fN46268, USA. http : / l pdf.tinnsdev.com / We b/3 5 / 694 5 / 35 6945 LABEL English .pdr?download=true Date Ac cess ed. July 3 , 2 0 1 3
. Dithiopy r. Weedscience.org. 2 0 1 3. http : // www . wec d s c ienc e . org/s umm ary /I l e rb i c i de .asp x . Date Accessed. June 6, 2 0 1 3. International Survey of Herbicide Resistant Weeds. 2013. o http : // www.weedscience.org/s ummary/MO A
. asp x . Date A c c esse d , Ju n

e 1 7 , 2013. Kline & Company
. 2005,20 0 7 , and 2012 Pesticide Fact S he et Numb e r 223. 1991. USEPA. http : // massmc.org

/ip m/do c s/ E PA Factsh e

et Dithiopyr.pdf

. Date Accesse d
. J une 6, 2013. US DA NASS. 2009 Nurs e ry and F loriculture Chemical Use.