Clopyralid - Registration of Scorpion III 3/96
New York State Department of Environmental Conservation
Division of Solid & Hazardous Materials
50 Wolf Road, Albany, New York 12233-7250
Phone 518-457-6934 FAX 518-457-0629
March 29, 1996
Mr. Robert D. Vatne
State Regulatory Affairs Manager
9330 Zionsville Road
Indianapolis, IN 46268-1054
Dear Mr. Vatne:
Re: Registration of the New Active Ingredient Clopyralid, Contained in
the Pesticide Product Scorpion III (EPA Reg. No. 62719-264)
DowElanco applied for New York State registration, on September 5, 1995,
for Scorpion III (EPA Reg. No. 62719-264) which contains the new active
ingredient clopyralid along with flumetsulam (Broadstrike), and 2,4-D
(2,4-dichlorophenoxyacetic acid). Scorpion III is a selective herbicide
for postemergence broadleaf weed control in field corn.
The water soluble packets contain 25% clopyralid, 9.3% flumetsulam and
50% 2,4-D. The maximum use rate of the product is 0.25 lb. of Scorpion
III per acre. This is equivalent to 0.063 lb. of clopyralid per acre,
0.023 lb. of flumetsulam per acre and 0.125 lb. of 2,4-D per acre.
Label language indicates that the maximum amount of flumetsulam which
can be applied per acre per year from the combination of any
flumetsulam-containing product is 0.07 pounds. The product is applied
by ground application to field corn once a year.
On December 14, 1994, the New York State Department of Environmental
Conservation (the Department) conditionally registered two products,
Broadstrike + Dual (EPA Reg. No. 62719-239) and Broadstrike + Treflan
(EPA Reg. No. 62719-222), also submitted for registration by DowElanco,
that contain flumetsulam (Broadstrike).
The Division of Fish and Wildlife (DFW) expressed concerns regarding the
potential toxicity of flumetsulam to non-target aquatic plants.
Therefore, as a condition of registration, DowElanco was to perform an
acceptable controlled mesocosm study to be completed and delivered to
the Department by October 31, 1995. DowElanco responded in a letter
dated January 31, 1995 that appropriate mitigation measures have been
taken to limit exposure to nontarget aquatic plant species and that a
mesocosm study was not warranted. The Department responded to DowElanco
in a letter dated February 15, 1995 that a mesocosm study would not be
required at that time. This letter also requested that DowElanco
contact Jim Colquhoun, Chief of the Division of Fish and Wildlife's
Bureau of Environmental Protection, regarding a runoff study to be
conducted by DowElanco with flumetsulam. A meeting was held on August
2, 1995 and additional information was submitted to DFW for review.
DowElanco has maintained that the information submitted is sufficient to
mitigate concerns for potential toxicity to nontarget aquatic plants.
In response to the application for registration of Scorpion III, the DFW
thoroughly revisited the additional information provided as a result of
the August 2, 1995 meeting. The DFW disagrees with the conclusion of
The Department has completed the review of the information supplied to
date in support of the pesticide product registration application for
Scorpion III, which contains the new active ingredient clopyralid.
Clopyralid and 2,4-D are not toxic to mammals, birds, or aquatic
organisms. However, the Department remains very concerned with the
potential for flumetsulam to cause toxicity to nontarget aquatic plants
The concerns are based on the high toxicity flumetsulam exhibited to
representative aquatic plants (Selenastrum capricornutum and Lemna
gibba) in the laboratory. Flumetsulam is stable to degradation by
photolysis in both soil and water, with average half-lives of 90 days
and 150 days, respectively. Laboratory and field studies show
flumetsulam to be persistent in soil and water and mobile. It is also
reported to leach, especially in well-drained and low organic matter
DowElanco has provided information derived from computer models (GLEAMS
and EXAMS II) and narrative data to simulate environmental effect
concentrations of flumetsulam after application at the maximum label
rate. The estimated loss in runoff ranged from 0.01 to 1.96h, with an
average of 0.14k. The United States Environmental Protection Agency
(EPA) estimated the loss of flumetsulam in runoff to be between 21k and
30k of the total application, based on the PRZM model. It is impossible
to determine which model is providing more reliable runoff predictions
without field validation specific to flumetsulam.
DowElanco stated at the August 2, 1995 meeting with the DFW staff that
model validations were currently being conducted to compare estimates to
actual field data on a wide range of pesticides for PRZM and GLEAMS. We
can expect results some time this year. According to DowElanco's most
recent data submission, model simulations were performed with the
Pesticide Leaching Model (PELMO) which was developed on the basis of the
PRZM model. PELMO, after modifications, accurately predicted runoff
from field experiments using the pesticides bifenox, dichlorprop-p, and
isoproturon. This model must be validated with other runoff experiments
using a wide range of chemicals before it can be used as a standard to
predict pesticide losses.
According to DowElanco's most recent submission, the Pesticide Root Zone
Model (PRZM-2) was discovered to overpredict atrazine runoff in four
field monitoring sites. The DFW assumes PRZM-2 is the most recent
version of PRZM. The study authors made modifications to the model to
improve its predictive capabilities for atrazine. The authors concluded
the modifications should be tested against other chemicals,
formulations, and environmental conditions and refined as necessary to
provide a larger validation. Flumetsulam was not used in any of the
aforementioned studies. No information was submitted comparing
flumetsulam to bifenox, dichloro-p, isoproturon, or atrazine.
In the absence of model validation, the DFW maintains a runoff study
using flumetsulam is needed to provide the information needed to resolve
Clopyralid is not very toxic in laboratory studies. Exposure of the
general public and applicators to clopyralid is expected to be low from
the labeled use of Scorpion III.
There are no chemical-specific federal or New York State drinking
water/groundwater standards for clopyralid. Based on its chemical
structure, clopyralid falls under the 50 micrograms per liter (ug/L) New
York State drinking water standard for an "unspecified organic
contaminant" (10 NYCRR Part 5 - Public Water Systems). This value of 50
ug/L should also be considered a potential State groundwater standard.
Stinger Herbicide (EPA Reg. No. 62719-73), Transline Herbicide (EPA Reg.
No. 62719-73) and Confront Herbicide (EPA Reg. No. 62719-92), also
submitted by DowElanco, have been previously reviewed by this Department
which contained clopyralid labeled for control of broadleaf weeds in
ornamental turf, various agricultural and industrial sites, and rights-
of-way and concerns were raised due to its high leaching potential and
concern for contamination of groundwater. The same concerns for
Scorpion III were not raised because the application rate of clopyralid
in this product is much lower than the rate for the clopyralid products
previously reviewed, and Scorpion III is applied only once a year
instead of the multiple applications allowed for the other products.
Also, Scorpion III is used on field corn only and the label prohibits
use on Long Island.
Scorpion III should not impact groundwater in New York State when used
according to label directions.
The Department has no objections to the registration of the active
ingredient clopyralid in New York State at this application rate.
However, there is an unresolved concern for the potential toxicity of
flumetsulam to non-target aquatic plants. Registration of additional
products which contain flumetsulam only heighten our concerns for
Therefore, the Department hereby accepts for conditional general use
registration Scorpion III (EPA Reg. No. 62719-264) which will expire on
December 31, 1997. The expiration date for Broadstrike + Treflan (EPA
Reg. No. 62719-222) and Broadstrike + Dual (EPA Reg. No. 62719-239) will
also be December 31, 1997. A December 31, 1997 expiration date should
provide adequate time for DowElanco to budget for this runoff study and
provide this Department with runoff data. The registration expiration
date for the remainder of the New York State registered DowElanco
products is December 31, 1996. At that time, DowElanco will have
to pay a renewal application fee for all products, including
Scorpion III, Broadstrike + Treflan and Broadstrike + Dual. The
continued registration of these three products past the December 31,
1997 date will depend upon the submittal and review of an acceptable
As a condition of this registration, Scorpion III (EPA Reg. No. 62719-
264), and the other two registrations which contain flumetsulam,
Broadstrike + Treflan (EPA Reg. No. 62719-222) and Broadstrike + Dual
(EPA Reg. No. 62719-239), DowElanco must perform an acceptable runoff
study to be completed and delivered to this Department by October 31,
1997. DowElanco will be required to notify this Department within
forty-five (45) calendar days of receipt of this letter regarding their
intention to conduct a runoff study.
If DowElanco chooses not to comply with the conditions of this letter,
the Department may propose to cancel the registration of Scorpion III,
Broadstrike + Treflan and Broadstrike + Dual.
The conditions of the runoff study are:
1. Application of flumetsulam, at the maximum rate of 0.07 pounds per
acre, to a small plot.
2. Application should be followed by irrigation, collection, and
analysis of the runoff.
3. The study should examine worst-case rainfall events as well as
4. Other variables that should be investigated are:
a. The length of time between a flumetsulam application
and the occurrence of a runoff event.
b. Differences in runoff resulting from different crop
or cover types.
c. The impact of slope on runoff.
The Department believes that the above conditions should be adequate to
demonstrate the concentrations of flumetsulam likely to be transported
off-site by runoff. There are standard industry, EPA, or possibly
American Society for Testing Materials (ASTM) protocols for this type of
study. An actual long term field study would not be necessary to
validate the models.
DowElanco is reminded that if in the future they apply for registration
of additional clopyralid containing products with a higher application
rate, multiple applications per year and/or additional sites, an
extensive review by the Department would be required.
Enclosed is the New York State stamped "ACCEPTED" label and the
Certificate of Registration.
Please contact Ms. Maureen Serafini, Supervisor of our Pesticide Product
Registration Section, at (518) 457-7446, if you have any questions.
Norman H. Nosenchuck, P.E.
Division of Solid & Hazardous Materials
cc: w/enc. - N. Kim/A. Grey - NYS Dept. of Health
N. Rudgers/R. Mungari - NYS Dept. of Agric. & Markets
D. Rutz/W. Smith - Cornell University