UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

JUN 2 4 2013 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: 

FROM: 

THRU: 

TO: 

BEAD Chemical Profile (BCP) for Registration Review: Picloram Salts and 

Esters Case (005101, 005102, and 005104) 

Biological 

Sunil Ratnayake, 

Analysis 

Biologist 

Branch \ 

r-\An ''''-flf'""'~ !.- ~ ~ 

Jihad Alsadek, Economist .J ~ A- · A-~ Science Information and Analysis Branch 

Stephen Smearman, Economist /i.J...., 61

f1. I _ ... 41 ~,., 

Economic Analysis Branch ~fA.t..V'J~vY'I.CY' ' 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Diann Sims, Chief ,iCl/L.~~~.,.........u Science Information and Analysis Branch 

Timothy Kiely, Chief ~ VVl ~ Economic Analysis Bran~'!( J 

Biological and Economic Analysis Division 503P) 

Christina Scheltema, Chemical Review Manager 

Risk Management and Implementation Branch 3 

Pesticide Re-evaluation Division (7508P) 

Product Review Panel Date: March 20, 2013 

INTRODUCTION 

The purpose of this document is to convey usage information and a broad overview of the pest 

management roles of picloram. 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 inf~rmation and data available to BEAD as of March 20,2013. 
Picloram was first registered as a pesticide in the U.S. in 1964 and the Registration Eligibility 

Decision was issued in 1995. This chemical belongs to the pyridine family of herbicides and it is 

a restricted use pesticide (RUP). According to the WSSA (Weed Science Society of America) 

mechanism of action classification picloram is identified as a member of the group 4 herbicides. 

Picloram is a systemic herbicide used for control of woody plants and a wide range of broadleaf 

weeds in range management programs. It can be applied as a pre-or post emergence treatment. 

Picloram is a synthetic auxin and this type of herbicides kills susceptible plants by mimicking the 

plant growth hormone auxin (indole acetic acid). Applications of picloram at effective rates, 

causes uncontrolled and disorganized plant growth that leads to plant death (Tu et al., 2001). In 

general, picloram is more toxic to broadleaf weeds than to grasses species. Picloram may be 

used with other herbicides such as bromoxynil, diuron, 2, 4-D, MCPA, triclopyr, and atrazine to 

broaden the weed control spectrum. Picloram is a restricted use chemical with long-term 

residual effects. No more than one pound a.e. should be applied per growing season for right-ofway and in other non-ag. sites, and application should be made every two years in forest sites. 

IDSTORY OF BEAD ASSESSMENTS FOR PICLORAM 

A search of the BEAD Official Records data base did not fmd any benefits assessments or 

Section 18s for picloram. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Picloram is formulated as emulsifiable, soluble concentrate, and as a solution-ready-to-use. 

Picloram can be applied by broadcast, spot treatment as foliar (leaf), bare soil spray, as a basal 

bark treatment, and/or by air as broadcast spray. 

USE SITES 

Agricultural Use Sites 

Picloram is an herbicide registered for use on barley, fallow, oats, wheat, pastureland, and in 

forestry. 

Non-Agricultural Use Sites 

Picloram is an herbicide registered for use on ornamentals, conservation reserve program land, 

non-agricultural sites, rights-of-way, industrial sites, storage yards, fencerows, industrial storage 

areas, and hedgerows. 

USAGE 

Agricultural Usage 

The use trend for picloram decreases during the 1998-2011 timeframe. Ninety-eight percent of 

the usage is on pastureland during this time period and decreased almost 50 percent during this 

time period, as presented in Figure 1. The remaining 2 percent is used on barley, fallow, and 

wheat. 

2 
Fi ·cultural Usa e Data for Picloram in Pounds A.I. on Pastureland 1998-2011) 

PoundsA.i. 

0 

8 N 

g g 8 N N N N 

Years 

Source: Proprietary Data, 1998 -2011 

~ 0 

N 

...... 

0 

0 

N 

~ 0 

N 

~ 0 

N 

0 

...... 

0 

N 

From 2007-2011, the annual total agricultural usage averaged approximately 810,000 pounds 

acid equivalent (a.e.) for 5.3 million treated acres with an overall application rate of0.2lbs. a.e. 

per acre, versus an overall application rate of0.1lb. a.e. for the long time period 1998-2011. 

On average, the states with the most agricultural usage in terms of pounds a.e. applied are Texas 

(26%), Oklahoma (12%), and Arkansas (10%), and the top states in terms of the total area treated 

are Texas (31 %), same percentage for Oklahoma (12%), and Arkansas (9%). 

(Proprietary Data, 2007-2011). 

Table 1, for the same time frame (2007-2011), shows the crops with the most use in terms of 

total pounds of active equivalent (a. e.) applied, and percent of total acres treated. 

Source: Proprietary Data, 2007-2011 

Agricultural Usage by Crop Reporting Districts 

Another measure of usage is the use intensity. In this analysis, the use intensity is expressed as 

the pounds a.i. applied per 1 ,000 acres of land in farms. This differs from the application rate, 

3 
which is expressed as the pounds a.i. applied per treated area. The average application rate for the 

period 2007-2011 is 0.2 lb. a.i. per acre. As shown in figure 2 the highest use intensity is 240 lbs. per 

1,000 acres ofland in farms. Figure 2 spatially represents picloram usage by crop reporting district 

for 2007-2010. The areas depicted in red on the map in Western Louisiana and Northern 

Arkansas is the pastureland areas. 

Non-Agricultural Usage 

Recent non-agricultural data are not available for this chemical; the most recent is for 2006. 

BIOLOGICAL ASPECTS RELEVANT TO PICLORAM 

Picloram is an herbicide used to control a variety of annual and perennial broadleaf weeds and 

woody species. Picloram is readily absorbed by plant roots, foliage, and it is readily translocated 

throughout plants. It can persist in an active form in the soil from several months to years, and 

can also be released from the roots of treated plants into the soil, where other non-target species 

may take it up and be injured or killed (Hickman et al. 1990). Examples of weeds successfully 

controlled using picloram include: leafy spurge (Euphorbia esula), knapweeds (Centaurea spp.), 

horsenettle (Solanum carolinense), milk weed (Asclepias L.), field bindweed (Convolvulus 

arvensis), and Russian thistle (Sa/sola kali) (Picloram K Specimen Label, 2013). 

It has been reported that yellow starthistle (Centaurea solstitialis) has developed resistance to 

picloram. In addition, presence of wild mustard (Sinapis arvensis) biotypes resistant to picloram 

has been reported in Manitoba, Canada that had been treated with herbicides with the mechanism 

of action similar to picloram (dicamba, MCPA, and mecoprop). Also, biotypes of carpet burweed 

(So/iva sessilis), a dicot, have developed resistance to clopyralid, picloram, and triclopyr in the 

New Zealand (International Survey of Herbicide Resistant Weeds, 2013). 

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON PICLORAM 

Additional information, in terms of pounds a.i. applied, average application rate, regional 

application, time of application, number of applications per year on non-agricultural sites, such 

as ornamentals, rights-of-way, industrial sites, from the registrant would improve future 

assessments of this chemical. 

REFERENCES 

Alligare, Picloram K Specimen label. Alligare, LLC, 2013. 

http://www.alligarellc.com/ products/PDFs/PICLORAM K LABEL.pdf Accessed on 

March 11, 2013. 

EPA. 1996. Re-registration Eligibility Decision http://www.epa.gov/oppsrrdl!REDs/0096.pdf. 

Accessed on Feb. 11, 2013. 

4 
Extoxnet. 2013 . http://extoxnet.orst.edu/pips/picloram.htm. Access date. Feb. 12, 2013. 

Hickman, M. V., Messersmith, C. G., and R. G. Lym. 1990. Picloram release from leafy spurge 

roots. J. Range Manage. 43(5):442-445. 

International Survey of Herbicide Resistant Weeds. 2013. 

http://www.weedscience.org/summary/MOASummary.asp Accessed on Feb. 25, 2013. 

Proprietary Data, 1998-2011 

Sabba, R. P, Ray, I. M., Lownds, N., and T. M. Sterling. 2003. Inheritance of resistance to 

clopyralid and picloram in yellow starthistle (Centaurea so/stitialis L.) is controlled by 

a single nuclear recessive gene. http://www.ncbi.nlm.nih.gov/pubmed/14691320. 

Accessed on March 12, 2013. 

USDA, 2007. Census of Agriculture. Online: 

http://www.agcensus.usda.gov/Publications/2007/index.asp. Accessed on March 13, 

2013. 

USDA, 2007-201 l. NASS Crop Reporting Districts. Online: 

http://www.ers.usda.gov/briefing/arms/resourceregions/resourceregions.htm#nass. 

Accessed on March 14,2013. 

5 
Appendix 

Figure 2. Picloram Use Intensity by Crop Reporting District (2007-2011) 

Average Pounds Per 

1,000 Acres of Farmland 

- <1 

2-4 

0 5-7 

8-13 

- 14-24 

This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level prepared by BEAD 

for use in the Environmental Fate and Effects Division documents. These maps are used to help visualize 

where the pesticide being considered is most likely to be used and can be helpful in scenario selection and 

placing the exposure assessment in context. CRDs are boundaries created by USDA NASS which are 

aggregates of counties. Pesticide usage is displayed as average pounds (for the years 2007-2011) per 1,000 

acres of farmland in a CRD to normalize for the variation in farmland between CRDs. Farmland acreage was 

obtained from USDA (2007). Farmland or "land in farms" is defined as follows: 

The acreage designated as "land in farms" consists primarily of agricultural land 

used for crops, pasture, or grazing. It also includes woodland and wasteland not 

actually under cultivation or used for pasture or grazing, provided it was part of 

the farm operator's total operation. Large acreages of woodland or wasteland 

held for nonagricultural purposes were deleted from individual reports during 

the edit process. Land in farms includes CRP, WRP, FWP, and CREP1 acres. 

Land in farms is an operating unit concept and includes land owned and 

operated as well as land rented from others. Land used rent free was reported as 

1 CRP: Conservation Reserve Program; WRP: Wetland Reserve Program; FWP: Farmable Wetlands Program; 

CREP: Conservation Reserve Enhancement Program 

6 
land rented from others. All grazing land, except land used under government 

permits on a per-head basis, was included as "land in farms" provided it was 

part of a farm or ranch. Land under the exclusive use of a grazing association 

was reported by the grazing association and included as land in farms. All land 

in American Indian reservations used for growing crops, grazing livestock, or 

the potential of grazing livestock was included as land in farms. Land in 

reservations not reported by reservation, individual American Indians or nonNative Americans was reported in the name of the cooperative group that used 

the land. In many instances, an entire American Indian reservation was reported 

as one farm (USDA, 2007). 

Usage is based on private market surveys of pesticide use in agriculture (Proprietary Data, 2007-2011). The 

survey data are limited to the states that represent the top 80-90% of acreage for the individual crops; 

therefore, use may be occurring in regions outside the scope of the survey. CRDs showing no usage of 

pesticides may be due to either the lack of pesticide use in the region or non-participation in the agricultural 

surveys. In addition, across the years, there may be variations in the specific crops included in the CRD 

survey. This may result in a lower annual average for the CRD. 

This map displays ratio data (i.e., average pounds per 1,000 acres of farmland) summarized at a very highlevel. Readers are strongly cautioned against trying to over interpret the map without examination of the 

underlying data. The underlying data may explain some of the many reasons that a Crop Reporting District 

may have .a high value for a particular active ingredient such as significant acreage (compared with the CRD 

as a whole) of a crop or crops with a high application rate and frequency of application. 

The reader should pay particular attention to the figure legends and realize that a map prepared for a 

particular chemical is not directly comparable to a map prepared for a different chemical. Scale and units of 

measurement do matter and may be different between maps. 

Sources: 

Proprietary Data. 2007-2011. 

USDA, 2007. Census of Agriculture. Online: http://www.agcensus.usda.gov/Publications/2007/index.asp. 

7