UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C ., 20460

MEMORANDUM

JUN 1 7 2010 OFFICE OF

CHEMICAL SAFETY AN D POLLUTION

PREV£NT!ON

SUBJECT: Addendum to the Docwnent "Evaluation of a Request for a Public Interest

Finding for the Conditional Registrati on of Aminocyclopyrachlor and

Aminocyclopyrachlor Methyl for Weed and Brush Control (DP#376722)"

[z....... "/t~u Ph,/lV's}J". , 7.1 .... ;0".( l u lCJ

FROM:

T HRU:

William Phillips, U. Ph.D_. Agronomist i::ct'// J "-

Biological Analysis Branch /

Biological and Economic Analysis Divisi (750 P)

Arnet Jones, Chief ---.....t; / L

Biological Analys is Branch ,1- :T.............. ahf)

Biological and Economic Analysis ivision ( 503P)

TO: Mindy Ondish

Fungicides Branch

Registration Division (7505P)

PRO DUCT REVIE W PANEL: June 16, 2010

BACKGROUN D

A request was submitted to the United States Environmental Protection Agency (Agency)

by the registrant E.1. DuPont de Nemours and Company (DuPont) to determine whether a request

for the conditional registration of a new active ingredient for the broadleaf herbicide

aminoeyciopyraehlor aeid (DPX-MAT28) and methyl (DPX-KJM44) (aminoeyclopyraehlor) is

in the public interest.

To make the determination whether a conditional registration is in the public interest

BEAD conducted an analysis that resulted in a memo' outlining the findings of this analysis.

The criteria by which BEAD evaluated this request were based on the 1986 Federal Register

Notice on public interest findings, and consisted ofthe following: I)that there is a need for the

new pestic ide that is not being met by currently registered pesticide s, and/or 2)that the

I Phillips. II. W. Evaluation of a Request for a Public Interest Finding for the Conditional Registration of

Aminocyc1opyrachlor and Aminocyc1opyrachlor Methyl for Weed and Brush Control (DP#376722)
benefits to use rs from the new pesti cide are greater than those from currently registered

pesticides or non-chemi cal control measures. In its review of the orig inal submission from the

registrant document, BEAD determined that the data on herbicide efficacy comparisons was

incomplete and lacked data rigor. Therefore, the information provided by the registrant for

aminocyclo pyrachlor failed to meet the criterion that new herbicide controls weed spec ies that

are not controlled by currently registered herbicides.

In addition to the efficacy of this herbi cide, the Age ncy was asked to evaluate two

additional ways in which the registrant claimed that aminocyclo pyrachlor could meet the

conditional registration criteria for being in the public interest. The registrant asserted that I) the

use of this herbi cide reduced the amount of herbicide appli ed when compared to older chemicals

and 2) the low volatility of this herbi cide would be a benefit in reducing phytoto xicity to nearby

plants. The evaluation ofthese two additional assertions by the registrant were deferred by

BEAD to RD, EFED, and BED as it was not BEAD's regulatory role to make these

determinations. Thu s, this addendum to the original document will not address these issues.

Since the time that the original document was written, BEAD has received 23 new data

sets for as many weed species from the registrant. The data from DuPont was from statistically

analyzed efficacy trials from several universitie s and included each weed species menti oned in

the original submission. Due to the large amount of data submitted and the short amount of time

allo wed for review, BEAD has selected leafy spurge as a model weed for the determination of

the comparative efficacy of aminocyclopyrachlor. This weed pe st was selected on the basis of

several factors. Overall, this weed was selected because ofthe significant problems associated

with controlling this weed species in various parts of the country. In addition, leafy spurge is

considered a "noxious" weed species by the US Departm ent of Agriculture (USDA). Through

their "TEAM Leafy Spurge" program, USDA ARS characterizes this weed as causing " ...

significant problems in the northern Great Plains by invading grazing lands f or cattle and

horses, reducing rangeland productivity and plant diversity, degrading wildlife habitat,

displacing sensitive species and drastically reducing land values. " BEAD considers these issues

important enough to warrant the selection ofthis species as a significant test of

aminocyclo pyrachlor's ability to control noxious and inva sive weeds as a potential alternative to

currently registered herbi cides as asserted by the registrant. The following are herbicides that

can be used to control weeds like leafy spurge and are registered for use in the same sites;

Aminopyralid, Bromacil, 2,4-D, Dicamba, Picloram, Triclopyr, Clopyrlid, Glyphosate, and

Imazap yr.

D ISCUSS IO:\

Leafy Spurge

Leafy spurge is a perenn ial weed that reproduces by an aggressive root system as well as

seed transported and spread by bird s and humans. It is con sidered a noxious weed that occurs

primarily in 35 of the United States? and its control is required by legal statute in 22 states.' The

2 Mitchell, R., C. Moffet, and R. Sosebeez. 2007. A Physiological Basis for Controlling Leafy Spurge on Nebras ka

Rangeland. Rob Mitchell, Corey Mocty, and Ron Sosebeez USDA Agricultural Research Service, Lincoln,

Nebraska. Publications from USDA·ARS I UNL Faculty. University ofNebraska - Lincoln

3 USDA ARS TEAM Leafy Spurge. http://www.team.ars.usda.gov/index.html

2
sites where this weed is found are mainly pasture, rangeland, grass prairies, as well as noncultivated areas. Leafy spurge is an economically important plant since it reduces viable forage

for high-grazing anima ls such as cattle and horses, as well as being toxic to these species. This

weed costs private landowners, federal agencies, and state governments millions of dollars in

control efforts.

Biolog ical and Cultural Control

Biological, cultural, and herbicidal controls should be used together in an integrated

system to control leafy spurge. Many ofthese systems will use insects, animal grazing, and

burning, cultivation, and herbicide applications. Control using insects include the release of flea

beetles, while the use of grazing as a method to control requires low grazing animals such as

sheep and/or goats. Research has demonstrated that using multiple grazing species can reduce

leafy spurge populat ion densities as much as 80-90% in three to five years using prescribed

stocking rates and specific herbivore types." Unfortunately, many animal production systems

focus on single species and as a result, the addition of different animal types would result in a

drastic change in operation for many ranchers. Cultural control consists primari ly ofbuming and

cultivation of areas that are infested with leafy spurge. Cultivation is a very effective tool for the

control of this weed and its spread; however, cultivation is very limited in remote areas of

rangeland and environmentally sanative areas. Overall, in combination these methods plus

conventional herbicides can result in the successful control of leafy spurge. More information on

biological and cultural control of leafy spurge is maintained at the USDA ARS TEAM Leafy

Spurge website.

5

Herbicide Control

The primary herbicides used to control leafy spurge are 2,4-D, aminopyralid, picloram,

and triclopyr. The registrant states that aminocyclopyrachlor should be considered a replacement

for these herbicides. In general, most of these herbicides are effective to some degree at

controlling leafy spurge; and when in combination as a tank mix with one another, in sequential

applications, or both, their efficacy can be enhanced. The herbicide that is most often

recommended to control leafy spurge is picloram." Picloram is commonly recommended to

control leafy spurge when in combination with 2,4-D. This combination is popular since it

allows for a reduced rate ofpicloram to be used, which reduces the per acre treatment cost. ' In

addition, it has been reported that the two herbicides working together have a higher efficacy

than each working alone. Nevertheless, the hallmark of an efficacious herbicide that will control

perennial weed species is long-term control.

4 S. Merritt. 2002. Specie s Grazing and Leafy Spurge, A Comprehensive, Easy-To-Read Manual On Using MultiSpecies Grazing As An Effective Leafy Spurge Management Tool. USDA-ARS TEAM Leafy Spurge Area-Wide

IPM Program. http://www.team.ars.usda.gov/grazingmanual.pdf

5 TEAM=The Ecological Area-wide Management. http://www.team.ars.usda.gov/index.html

6 Vegetation Management Guide, Missouri Department of Conservation.

http://mdc.mo.gov/nathis/exotic/vegmawsixteen.htm

7 Goodwin, K. R. Sheley, R. Nowierski and R. Lym. Leafy Spurge :Biology, Ecology and Management

3
NEW DATA SUO"1 ISSIO:\ AND EVALUATION

Data Submission

The efficacy data provided by the registrant was from a set oftrial results conducted by

cooperators from 24 university researchers. University herbicide evaluation trials are generally

conducted in field plots where various herbi cide treatments are appl ied to specific plots (see

hypothetical example in Table 1). Usually, each herbicide is applied to three plots to replicate

treatment effects. These plots contain a species, or multiple species, of target weeds. The data

gathered from these plots. among many types, are the percent of weeds that are controlled.

These eva luations are conducted at various preplanncd intervals. Table 2 provides an example of

how the data from university trials are anal yzed for each herbicide at three different times

following treatment.

Table I . A hypothetical example of the structure of a single university herb icide trial: Evaluation

of herbicide A l control ofweedZ versus industry standard herbicides at the University of X

research farm.

Rate

Treatments Ibs ai/A

Al 10

Al 5

B3 .5

C7 1

"OAT-Days Afte r Treatment

20 DAT'

% Co ntrol

86a

Oc

20b

l 5b

Evaluation Times

60DAT

90a

25b

20b

5c

100 DAT

80a

75a

Ob

Ob

The data submitted by the registrant includ ed statistical analyses from each university trial

for eac h weed species (e.g. weed species A, university 1; weed species A, university 2.. .). In

order to facilitate a comp rehensive comparative analysis for each weed spec ies, the registrant's

analyses would needed to have been conducted by analyzing together the data from all studies.

Since the data analysis provided was not conducted in this manner BEAD's rev iew of the

efficacy data regarding these herbicide uses cannot be quantitatively evaluated across university

trials, nor can the mean treatment effects be statistically compare d across evaluation dates.

However, this ana lysis will discuss the effec ts of herbicide treatments within OATs (e.g. Table 2,

20 OAT, 60 OAT, 100 OAT) quantitatively whil e discussing the data across OATs (e.g. Table 2,

Treatment A l at 20 OAT versus IOODAT) qualitatively.

Data Analysis

University trials selected for this review had to include one ofthree aminoeyclopyrachlor

treatments, 0.089, 0.112, 0.178, or 0.187 pounds acid equivalent per acre (lbs ac / A). The

reason for this requirement is that these rates, while low, are well within the labeled rates and are

the most consistent across trials. The next two criteria that each trial was required to have are

ratings conducted at approximately 30 OAT and 365 OAT. These two dates would allow a

determin ation ofthe efficacy in the short term as well as the long term. Also, the selected studies

must have contained at least one of the herb icides, 2,4-0, arninopyralid, pic1orarn, or triclopyr

4
alone and not in combination with other herbicides. The reason for only evaluating the

registrant' s herbicide with these chemicals alone and not in combination is because the

evaluation criteria is that there is a need for the new pesticide that is not being met by

currently registered pesticides. The criterion is not that there is a need for the new pesticide

that is not being met by curre ntly registered pesticides and/or pesticide combinations.

F INDINGS

The data for all herbicides except picloram were very sparse, however, the data from the

trials that included 2,4-D, aminopyralid and triclopyr demonstrated that late season control of

leafy spurge did not come close to the minimum industry standard of70% control (Table 2).

However, out ofthe 16 trials that included picloram, five of the studies provided late season

control that was above well above 70%. Of the five, in trial number one the late season control

rating was 77%, however this was not statistically different than 43%, and in trial number two

the late season rating was 72% which was not statistically different from 69%. Overall, the longterm controls with picloram in over 80% of the studies were below the industry standards.

Picloram is usually tank mixed with 2,4-D in order to reduce the amount ofpicloram while

maintaining, or often increasing the herbicide efficacy, and also reducing the cost. In fact, data

from one university trial demon strated that the combination of 2,4-D and picloram resulted in

control of 100% and 80% at 43 and 348 DAT, respectively. However, the analysis required in

order to evaluate a pesticide as a replacement for currently registered pesticides is based on the

efficacy of the individual herbicides.

Aminocyclopyrachlor data for the 17 university trials meeting the selection criteria of

having data for the rates 0.089, 0.11 2, 0.178, or 0.187 lbs ae fA were similar for short term

control as well as long-term (- 365 DAT) control (Table 2). With the exception oftwo of the

university research trials, all rates had long-term control ratings for leafy spurge well above the

industry standards.

The two studies that contained data for the lowest rate of aminocyclopyrachlor contained

data for the high rate that was above the industry standard. In university trial number three there

was only a single rating taken at 315 DAT. The control rating for the 0.0891bs ae fA rate was

47%, however the rating for the 0.l871bs ae fA was 93%. In another university trial, number

eight, the percent control for the lowest rate of 0.089 lbs ae fA at 55 DAT was 57%, which was

significantly lower than the rating of95% for the 0.187 lbs ae fA taken on the same date. In

addition, at 358 DAT the lower rate was below industry standards (62%) and the high rate was

not significantly different from 100% control. It is unknown why in both of these trials those

results in the ratings for the 0.089 Ibs ae fA rate were lower for each evaluation period than the

0.187 Ibs aefA rate .

F INDING

BEAD has reviewed the new data analyses and has detennined that in some cases 2,4-D,

aminopyralid, picloram, and triclopyr control of leafy spurge at approximately 30 DAT

performed up to the industry standard of 70% or above; however, at the one year mark

aminocyclopyrachlor consistently controlled leafy spurge above the industry standard while the

aforementioned herbicides did not. Therefore, the late season results of the efficacy analysis

5
meet the criteria that there is a need for the new pesticide that is not being met by currently

registered pesticides.

6
Table 2. Efficacy results of submitted data form DuPont regarding the conditional registration of aminocyclopyrachlor.

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