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2ee Recommendation for Rodeo/Hydrothol Tank Mix 4/97

New York State Department of Environmental Conservation
Division of Solid & Hazardous Materials
Bureau of Pesticides & Radiation
Pesticide Product Registration Section
50 Wolf Road, Albany, New York 12233-7257
Phone 518-57-7446     FAX 518-485-8990

                                    April 17, 1997

Ms. Tonya R. Staniforth
State Registration Specialist
Monsanto Company
8OO N. Linden Boulevard
St. Louis, MO 63167

Dear Ms. Staniforth:

Re:  FIFRA 2(ee) Recommendation For - Rodeo Emerged Aquatic Weed and Brush
     Herbicide (EPA Reg. No. 524-343) Tank Mix with Hydrothol 191 Aquatic
     Algicide and Herbicide (EPA Reg. No. 4581-174) For Control of Emerged
     Aquatic Weeds

     The New York State Department of Environmental Conservation has approved
your FIFRA 2(ee)request to tank mix the above herbicides to control emerged
weeds in all bodies of fresh and brackish water which may be flowing,
nonflowing or transient. The use rate will be no greater than 1% by volume of
Rodeo and 0.1% by volume of Hydrothol 191.

     This request was reviewed by the NYS Department of Environmental
Conservation, Bureau of Environmental Protection. No adverse impacts were
anticipated from the proposed application.

     The recommendation calls for mixing a solution with 1% Rodeo with 0.1%
Hydrothol 191 in water, and applying treatments of 100 gallons per acre by
hand-held equipment to emergent vegetation. According to the Rodeo label, the
highest application rate of Rodeo alone to "Annual Weeds" is a 3/4 (0.75)
percent solution. This is a lower application rate then the Rodeo/Hydrothol
mixture calls for. However, under the list of target annual weed species on
the label there were no aquatic plants. Most aquatic emergent vegetation are
listed under the "Perennial Plants" section. The label specifies application
rates for each individual target perennial weed species. All application rates
equal or exceed the 1% solution of the mixture except for cattail, American
lotus, phragmites, and spatterdock, which are limited to a 0.75% solution.
Since the label allows the use of up to a 1.5%  solution on most aquatic
emergent vegetation, the application of the 1% solution with the mixture to
the few plants that are controlled with a 0.75% solution should not be
environmentally harmful by itself.

     Similarly, the 0.1% solution of the Hydrothol 191 in the  proposed
mixture is well below the labeled application rate for Hydrothol 191 alone.
Given that there are 908 grams AI in a gallon of Hydrothol 191, a 0.1'
solution by volume would only contain 0.9 grams. Applied to a one acre-foot
volume of water, the resulting concentration of AI would only be 0.73 ppb.
This is well below the usual treatment concentration of 1 ppm. The application
of a 0.1% solution of Hydrothol 191 in a Rodeo/ Hydrothol mixture would not,
of itself be expected to be environmentally harmful.

     Anyone using Rodeo Herbicide under this recommendation must have the
recommendation in their possession at the time of application.

     If you have any questions on this matter, please contact Betty Seeley, of
my staff, at (518) 457-7446.


                                     Maureen P. Serafini
                                     Pesticide Product Registration Section


cc:  R. Mungari - NYS Dept. of Agriculture and Markets
     B. Smith - Cornell University