UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

JUN 12 2013 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile for Registration Review: 2,4-DP-p (Dichlorprop-p) Case 

(2,4-DP-p acid, 2,4-DP-p dimethylamine salt (2,4-DP-p DMAS), and 2,4-DP-p EHE) 

(031402, 031403,031416,031464 and 031465) 

FROM: 

THRU: 

Bill 

Biological 

Phillips, 

Analysis 

Ph.D. Agronomist 

Branch ~ 

~ 

Sepehr 

Science 

Haddad

Information 

, Environmental 

and Analysis 

Protection 

Branch 

Special 

:;;/' 

is• ~ ~ ~ ~ ""' 

Derek Berwald, Ph.D. Economist ~~ ___.,.~~~.,-- Economic Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Timothy Kiely, Chief a VV\ ~ Economic Analysis Branch 

Biological and Economic Analysis Di ·sion (7503P) 

TO: Christina Scheltema, Chemical Review Manager 

Risk Management and Implementation Branch 3 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel date: April17, 2013 

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 registration status 

of 2,4-DP-p and eventually the general public. This document builds upon the data already 

provided in the usage and label use data packages that are also provided to Registration Review 

teams by BEAD. The document is based on information and data available to BEAD as of March 

20, 2013. 

2,4-DP-p, or dichlorprop-p, is a postemergence herbicide that controls actively growing annual 

and perennial broadleafweeds, trees and brush. In lawns, turf and pasture 2,4-DP-p controls 

such hard to control broadleafweeds as dandelion (Taraxacum officina/e) and ironweed (Veronia 

altissima) while on roadsides, industrial sites, rights-of-way, and forests many aggressive perennial 

weed species plus tree and brush species, such as multiflora rose (Rosa multiflora), are 

controlled. 

2,4-DP-p is a synthetic auxin herbicide that is in the Weed Science Society of America group 4 

herbicides. The "-p" designation in the active ingredient (ai) indicates that this is the isolated 

"R" isomer, or the active fraction of the ingredients. Based on the chemistry of this herbicide it 

is considered volatile (vapor pressure 1 x 1 o-s Pa (20 C)) and has little soil activity (Senseman, 

2007). 

The mechanism of action of this herbicide is not well understood but the chemical is thought to 

act much like the endogenous plant hormone auxin. Auxins are primarily responsible for cell 

elongation and cell division. The mode of action of this herbicide is abnormal cell growth and 

elongation at the growing points and plant nodes, leaf attachments, and internodes, length of 

stem between nodes. The abnormal growth results in a distorted and constricted vascular system 

and ultimately total blockage of the vascular system. 

This herbicide is used in premixes of multiple herbicides that are broadcast over lawns and turf 

in order to control difficult to manage broadleaf weeds. Overall this is the predominant use of 

this herbicide with 60% of the annual total of four million pounds applied. This herbicide is 

commonly formulated into ready-to-use turfgrass products that contain multiple herbicides as 

well as some containing fertilizers. These products are used to control a broad spectrum of 

weeds, primarily broad leaf weeds, in a variety of turfgrasses in commercial and homeowner 

settings. One of the most common product mixtures is 2,4-D+dichlorprop-p (2,4-DP-p) 

+mecoprop-p, which is used to control numerous problematic broadleaf weed species in 

turf grass. 

Another area where this herbicide is used is in the control of trees and brush. Applications to 

trees and brush are via "spray to wet" foliage using water as the diluent and several specialized 

methods that sometimes include mixing the herbicide with oil or diesel fuel. One of the 

application methods using the oil or diesel fuel mixture is the basal bark application where the 

lower trunk of the tree is treated. In addition, this mixture can also be applied as a cut-stump 

treatment where applications are made to the freshly cut stump of a tree. This type of treatment 

is used to prevent any regrowth of the tree from the stump or any below ground vegetative 

propagules. Additionally, 2,4-DP-p can be applied as a frill treatment where the tree is cut into 

with an axe around the circumference of the lower trunk and the inside of the cut is then treated 

with the herbicide mixture. 

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The herbicide 2,4-DP-p ( dichlorprop-p) was initially registered in 1968. The Reregistration 

Eligibility Decision (RED) document was issued in 2007. As a part of the RED the use of aerial 

application was removed from the label and changes were made to the use rate. BEAD has not 

identified alternatives or evaluated the benefits to 2,4-DP-p in past work, including the RED 

process, so little background information is available. 

COMMON FORMULATIONS AND APPLICATION METHODS 

2,4-DP-p is formulated as granular, emulsifiable and soluble concentrate, wettable powder, 

Ready-to-Use solution. Methods of application are by boom sprayers, handheld nozzle or wand 

sprayers, knapsack sprayers, and granular spreaders. 

USE SITES 

Agricultural Use Sites 

2,4-DP-p is registered for use on pasture. 2,4-DP-p is not registered for any food crops in the 

United States. 

Non-agricultural Use Sites 

2,4-DP-p is registered for use on ornamental lawns, recreational turf, sports fields, sod farms, 

roadsides, industrial sites, rights-of-way, and forests. 

USAGE 

Agricultural Usage 

Note: all rates in this document are expressed in pounds acid equivalent (a.e.). Acid equivalent 

is the acid portion of the active ingredient (a.i.). 

Based on private market usage data from 1998-2011, agricultural usage averaged approximately 

8,000 pounds a. e. on approximately 24,000 acres of pasture treated. The average rate over this 

time period was 0.334 pounds a.e./acre. Pasture was the only site for which private market usage 

data was reported. Figure 1 presents 2,4-DP-p (dichlorprop) usage in pounds a.e. over the 1998-

2011 timeframe. Figure 2 presents total area treated in acres over the same time frame 

(Proprietary Data, 1998-2011 ). The use of 2,4-DP-p has fluctuated over time, but there is no 

discernible trend. 

3 
0 

1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Years 

Source: Proprietary Data, 1998-2011 

FIGURE 2. 2,4-DP- Use on Pasture Total Area Treated in Acres (1998-2011) 

100,000 . 

0 -

1998 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Years 

Source: Proprietary Data, 1998-2011 

According to a previous BEAD analysis (2013), nationally less than one percent of pasture is 

treated with 2,4-DP-p. Generally, such a low percentage would indicate that a chemical plays a 

very minor role in pest control because, for example, target pests are not that important or more 

cost-effective alternatives are available. In this case, however, it needs to be considered that 

pasture production is a very low-input activity in comparison to crop production. Further, use of 

2,4-DP-p on pasture appears to be geographically concentrated. The states with the highest use 

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of2,4-DP-p on pastureland in the 2007-2011 timeframe are listed in Table 1. The majority of 

use is in Missouri (70%), followed by Tennessee (17%) (Proprietary Data, 2007-2011). This 

information should be used with caution, because these data are from surveys where there are 

very few samples in the survey that show use of2,4-DP-p. 

TABLE 1. States with Highest Use (Missouri & Tennessee) of2,4 DP-p- Percent of Total 

Lbs. Applied, Total Acres Treated, and Average Application Rates from 2007 to 2011 

State %Total Lbs %Total Average Annual 

A.E. Applied Acres Application Rates 

Treated (Lbs A.E./A) 

Missouri 70% 74% 0.294 

Tennessee 17% 17% 0.315 

Source: Proprietary Data, 2007-2011 

Non-Agricultural Usage 

In terms of non-agricultural usage, data are available from Kline & Co. up until 2006, but since the 

data are dated, the information for non-agricultural usage included in this section is based on 

information provided to the Agency by the 2,4-DP-p Task Force (registrants of2,4-DP-p) and 

reflected in the 2007 RED. The Task Force provided information stating that the majority of2,4-DPp is co-formulated with other chlorophenoxy herbicides for use on residential lawns, with smaller 

usage in other recreational turf and other non-agricultural grassy areas. Based on usage information 

provided by the 2,4-DP-p Task Force in 2007, total annual domestic usage of2,4-DP-p is 

approximately 4 million pounds: 60% is applied to residential turf, 10% is applied to sod farms, 9% 

is applied to golf courses 8% is applied to sports turf, 8% is applied to commercial turf; and 5% is 

applied to uncultivated non-agricultural land. According to the Task Force, geographical use areas 

for applications to turf are in roughly the following descending order: Midwest, Northeast, South, 

Northwest, and West (U.S. EPA, 2007). 

ROLE OF PESTICIDE IN PEST CONTROL 

This herbicide is an important component in controlling many of the problematic broadleaf 

weeds in homeowner and commercial turf grass by broadening the spectrum of weeds that these 

product mixtures can control. For homeowners products containing this herbicide are easy to use 

and convenient for the control of aesthetically displeasing weeds such as dandelion. In addition 

to the turf grass use there are those uses that are important but for which there is not a lot of 

chemical required, such as brush and tree applications. Pasture use is small and does not require 

a lot of chemical; however, BEAD is unaware of whether this use is important to pasture weed 

control. 

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INFORMATION THAT MAY BE USEFUL FOR BEAD'S FUTURE WORK ON 

2,4-DP- p 

BEAD is unsure why the majority of the agricultural use is centered in the state of Missouri, or 

why specific areas show up as high use areas in the private data. In addition, BEAD does not 

have data to provide information on the current use of this herbicide in turf grass other than what 

was provided in the RED. If these areas and uses are considered significant in the future 

registration review risk assessments the task force may need to provide some information 

regarding these uses. 

REFERENCES 

BEAD. 2013. 2,4-DP Screening Level Usage Analysis. Biological and Economic Analysis 

Division, Office of Pesticide Programs, US Environmental Protection Agency. January 30. 

Proprietary Data. 1998-2011. 

Senseman, S.A. 2007. Herbicide Hand Book Ninth Edition. Weed Sci. Soc. of Am. 810 E. 

lOth Street, Lawrence, KS 66044-8897. U.S.A. 

USDA, 2007. Census of Agriculture. Online: 

http://www.agcensus.usda.gov/Publications/2007/index.asp. 

U.S. EPA, 2007. Reregistration Eligibility Decision for Dichlorprop-p (2,4-DP-p). Online at: 

http://www .epa. gov I oppOOOO 1 I chem _search/reg_ actions/reregistration/red_ PC-031402 _ 2 9-Aug07.pdf 

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