imazethapyr Major Change in Labeling for Pursuit Herbicide 10/96
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
October 15, 1996
Ms. Michaeleen E. Linahan
State Registration Manager
Agricultural Research Division
American Cyanamid Company
P.O. Box 400
Princeton, NJ 08543-0400
Dear Ms. Linahan:
Re: PURSUIT Herbicide, EPA Reg. No. 241-310 - Major Change in Labeling
Adding Use on Alfalfa, and PURSUIT DG Herbicide, EPA Reg. No. 241-350
Application for Registration.
The New York State Department of Environmental Conservation (DEC) has
reviewed and accepted for registration in New York State the
applications to register the referenced pesticide products containing a
major change in use for imazethapyr. Both products are classified as
general use pesticides in New York State.
American Cyanamid Company submitted an application and supporting
documentation on January 23, 1996 for the registration of a major new
use of PURSUIT Herbicide (EPA Reg. No. 241-310) on alfalfa. PURSUIT
Herbicide contains the active ingredient, imazethapyr, and was
previously registered for use on soybeans. The new use on alfalfa
constituted a Major Change in Labeling because the use rate was 50%
higher than the previously registered uses and because alfalfa is a very
large crop in New York State. American Cyanamid Company also submitted,
on January 30, 1996, an application for the new formulation PURSUIT DG
Herbicide (EPA Reg. No. 241-350) for the same uses.
The data packages for these products were reviewed by DEC's Division of
Fish, Wildlife, & Marine Resources (DFW&MR); our Technical Support &
Laboratory Services Section (TS&LS); and the New York State Department
of Health (NYSDOH). We have concluded that the use of the products as
labeled is not likely to result in significant adverse impacts to human
health or the environment in New York State.
The DFW&MR Bureau of Environmental Protection (BEP) did not object to
registration. According to their aquatic and terrestrial models,
imazethapyr is not toxic to fish, aquatic invertebrates, aquatic plants,
nontarget insects, mammals, or birds on an acute and chronic basis.
Bioaccumulation in the environment is also highly unlikely. Therefore,
labeled use of imazethapyr should not adversely impact the fish and
wildlife resources of New York State.
NYSDOH stated in their review that their previous review of imazethapyr
during initial registration did not identify any sign)ficant
toxicological concerns and that a current search of the literature did
not find any sign)ficant new information on the toxicity of imazethapyr.
Neither PURSUIT Herbicide nor PURSUIT DG Herbicide was very toxic
following acute oral, dermal or inhalation exposures in rats. PURSUIT
Herbicide did not cause sign)ficant irritation to skin or eyes, but
PURSUIT DG Herbicide was reported to be moderately irritating to eyes
and slightly irritating to skin. With regard to crop residues, based on
their evaluation of the toxicity of imazethapyr and the food residue
data, NYSDOH concluded that the use of PURSUIT products on alfalfa does
not appear to pose sign)ficant dietary exposure potential or risks.
There are no chemical specific federal or State drinking water standards
for imazethapyr. Based on its chemical structure, imazethapyr falls
under the 50 micrograms per liter general drinking water standard for an
"unspecified organic contaminant" (10NYCRR Part 5 - Public Water
The TS&LS Section stated in their review dated September 17, 1996 that
they did not object to the registration of PURSUIT on alfalfa. They
conducted computer modeling using the LEACHP model with the following
Koc of 97
Aerobic 1/2 life = three years
Application rate = 1.5 oz. A.I. per acre
Degradation rate = 6.0 x 10 -4
The modeling predicted that potential concentrations of imazethapyr
would not exceed 30 micrograms per liter in groundwater for Howard soils
nor about 25 micrograms per liter in groundwater for Riverhead soils.
In addition, field dissipation studies done with an application rate of
2 oz. A.I. per acre per season (one and one third times the labeled
rate) in a permeable sandy loam indicated that the half life is in the
two to four month range which is less than the three years predicted in
Only one major degradate was found, 5-ethyl-3-pyridine carboxylic acid
at 19.8%, but it was found during the aqueous photolysis study. Aqueous
photolysis is not a significant factor in the breakdown of the parent
Based on the environmental fate data review, the United States
Environmental Protection Agency's comments and the computer modeling, it
is the opinion of the TS&LS staff that the use of imazethapyr will not
cause a groundwater impact in New York State when used according to
label directions. They did state, however, that, if higher application
rates were proposed in the future, they will probably cause adverse
groundwater impacts. Therefore, should American Cyanamid propose
additional use patterns with an increased application rate in the
future, please be prepared to address the issue of impact to New York
State groundwater with definitive analytical data.
After consideration of the reviews by NYSDOH, DFW&MR, and by the TS&LS,
the Department has determined that registration of the Major Change in
Labeling (MCL) for the use of both PURSUIT Herbicide products on alfalfa
in New York State is appropriate.
If you have any questions regarding the above, please contact Frank
Hegener, of my staff, at (518) 457-7446.
Norman H. Nosenchuck, P.E.
Division of Solid & Hazardous Materials
cc: w/enc. - D. Rutz/W. Smith, Cornell University
N. Rudgers, NYS Dept. Of Ag. & Mkts.
N. Kim/A. Grey, NYS Dept. Of Health