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Pyriproxyfen - Registration of a Major Change of Label for Esteem® 3/01

New York State Department of Environmental Conservation
Division of Solid & Hazardous Materials
Bureau of Pesticides Management
Pesticide Product Registration Section
50 Wolf Road, Albany, New York 12233-7254
Phone: (518) 457-7446 FAX: (518) 485-8990

March 23, 2001


Mr. Harry Radke
State Registration Project Manager
Valent U.S.A. Corporation
1333 North California Blvd., Suite 600
P.O. Box 8025
Walnut Creek, CA 94596-8025

Dear Mr. Radke:

Re: Registration of a Major Change in Labeled (MCL) Use Pattern for the Active Ingredient Pyriproxyfen Contained in the Pesticide Product Esteem® 0.86 EC Insect Growth Regulator (EPA Reg. No. 59639-95)

    The New York State Department of Environmental Conservation ("The Department") has completed review of your application (received 09/30/99) and supplemental information supplied to date regarding registration of the referenced pesticide product in New York State. The subject application and data package were deemed complete for purposes of technical review on March 15, 2000 following one determination of incompleteness. Pursuant to the review time frame specified in ECL §33-0704.2, a registration decision date of August 12, 2000 was established. By mutual agreement, the registration decision date was subsequently waived to allow Valent U.S.A. Corporation (Valent) to respond to issues raised in the ecological effects risk assessment.

    Esteem® 0.86 EC Insect Growth Regulator (11.23% pyriproxyfen) is an alternate brand name for Knack® Insect Growth Regulator (EPA Reg. No. 59639-95). Esteem® is labeled to control certain insects on apples, pears and walnuts. During the technical review, Valent submitted amended product labeling bearing new almond and citrus crop uses. The maximum Esteem® application rate on crops (apples and pears) relevant to New York State is 32 fluid ounces per acre per season, which is equivalent to 0.22 pounds pyriproxyfen per acre per season.

    Previously registered use patterns for the active ingredient pyriproxyfen include products for indoor non-food/feed, indoor residential, domestic animal, indoor (greenhouse, lath and shadehouse) and outdoor ornamental, and outdoor perimeter area applications. The proposal to register a pesticide product bearing terrestrial food crop uses represents a MCL for pyriproxyfen in New York State.

    The Department conducted toxicological, environmental fate and ecological effects risk assessments for pyriproxyfen and the Esteem® formulation.


    Esteem® 0.86 EC Insect Growth Regulator is identical in formulation to Distance® Insect Growth Regulator (EPA Reg. No. 59639-96). The toxicological properties of Distance® and the active ingredient pyriproxyfen were previously reviewed by the Department (reference correspondence from S. Hammond to H. Radke and M. Serafini to H. Radke, October 19, 1999 and June 29, 2000, respectively).

    Neither the formulated product nor the active ingredient was very toxic on an acute basis to laboratory animals by the oral, dermal or inhalation routes of exposure. Whereas, the formulated product was moderately irritating to rabbit skin and mildly to moderately irritating to their eyes, the active ingredient was not very irritating to animal eyes or skin. Neither the formulated product nor the active ingredient caused dermal sensitization (tested in guinea pigs). In addition, the active ingredient pyriproxyfen did not cause oncogenic or reproductive effects and was negative in several genotoxicity studies. Some developmental effects (at maternally toxic doses) were reported in rats, but not in rabbits. The United States Environmental Protection Agency's (USEPA) Office of Pesticide Programs developed a reference dose (RfD) of 0.35 milligrams per kilogram body weight per day (mg/kg/day) based on a no-observed-effect level (NOEL) of 35 mg/kg/day in a two-year rat feeding study (decreased body weight of female rats at 183 mg/kg/day) and an uncertainty factor of 100.

    The USEPA established tolerances for pyriproxyfen in or on wet apple pomace at 0.8 parts per million (ppm), pome fruits at 0.2 ppm and walnuts at 0.02 ppm. The USEPA estimated that chronic dietary exposure to these residues would be 0.8 percent of the RfD for the general United States population, 1.2 percent for non-nursing infants and 2.2 percent for children 1 to 6 years old. This chronic exposure analysis is based on the assumption that 100 percent of crops are treated and contain tolerance level residues.

    There are no chemical-specific federal or State drinking water/groundwater standards for pyriproxyfen. Based on its chemical structure, pyriproxyfen falls under the 50 micrograms per liter (μg/L) general New York State drinking water standard for an "unspecified organic contaminant" (10 NYCRR Part 5, Public Water Systems).

    The available information indicates that use of pyriproxyfen for control of certain insects on apples, pears, and walnuts should not pose significant risks to workers or the general public. While the Esteem® product can be somewhat irritating to eyes and skin, the label requires that applicators wear a considerable amount of personal protective equipment, which should mitigate direct contact.


    Certain required USEPA Data Evaluation Records (DERs) were not available, however, sufficient information was available to determine potential impacts to ground and surface water.

    The input parameters for the Department's groundwater model (LEACHM) were taken from the DERs or from USEPA's Environmental Fate and Effects Division (EFED) memoranda dated March 27, 1996 and July 13, 1999. Using Riverhead soil, an application rate of 0.215 pounds pyriproxyfen/acre/year, a Koc of 11,600 for the parent and 85 for the degradate PYPAC (7.6%) and an aerobic half-life of 9 days, the modeling indicated no parent or degradate in the leachate in the ten year modeling cycle.

    Based on the low application rate, very high parent Koc, very short half-life and LEACHM modeling, it does not appear that use of Esteem®, as labeled, will impact ground or surface water in New York State.


    Esteem® is labeled for control of Codling moths, leaf rollers, scale insects, leaf miners, aphids, and pear psylla on pome fruits. Applications of 10 to 16 fluid ounces per acre in 75 to 400 gallons of water are made at targeted pest life stages. No more than two applications or 32 fluid ounces may be applied per season. Esteem® may not be applied within 45 days of harvest.

    Pyriproxyfen is practically non-toxic to birds or mammals. It is highly toxic to fish and freshwater invertebrates, and very highly toxic to marine invertebrates. Freshwater fish reproduction is affected at low ppb concentrations. Freshwater invertebrate reproduction is affected at low part per trillion concentrations. Freshwater invertebrate life cycle studies were conducted with two major degradates identified as PYPAC and 4'-OH-pyr; both affected reproduction at low ppb concentrations. PYPAC may be highly mobile in soil, 4'-OH-pyr is likely to exhibit low mobility. The environmental fate of both is poorly characterized.

    Potential ecological impacts of Esteem® were modeled using the Department's MAMTOX, AVTOX and AQUALIFE models. All toxicity and fate parameters for modeling inputs were taken from the data package.

    MAMTOX and AVTOX modeling indicate low potential for mammalian or avian toxicity.

    AQUALIFE runoff modeling was conducted for a single application at the 10 oz/acre rate and two applications at 16 oz/acre. It was assumed that 50% of the applied material was intercepted by the target plants and was unavailable for runoff. The 36-day field dissipation rate was used to calculate the parent compound residue remaining from the first application in the two application scenario. Of the applied precipitation, 60% was assumed to reach the model pond.

    The mean aqueous photolysis half-life of pyriproxyfen in shallow clear water is 4 days, other aquatic degradation pathways are considerably slower so it is possible for it to persist in deeper waters. The AQUALIFE model does not consider chronic effects if a chemicals shortest aquatic half-life is less than 10 days. If the predicted water concentrations exceed toxicity thresholds by a large degree it is possible to get chronic exposures even with compounds with relatively short half lives. Given the extreme reproductive sensitivity of aquatic invertebrates to this compound, the half-life in water was set at 11 days to evaluate the potential for chronic effects in situations where photolysis is reduced, and to determine if chronic exposures might occur before water concentrations fall below effects thresholds through degradation.

    No acute toxicity thresholds were exceeded in either modeled scenario. The predicted pyriproxyfen concentration in the model pond resulting from a runoff event occurring after one application at the lowest label rate exceeds the daphnia chronic lowest-observed-effect level (LOEL) and NOEL at all three runoff levels and in all pond depths, except at the lowest runoff rate in the 6 foot depth. The concentration in 6 feet of water at the low runoff rate is predicted to be 30 parts per trillion (ppt). The daphnid LOEL is 31 ppt. Although technically the concentration did not exceed the threshold, being only one part per trillion lower it can be considered equal to it. The pyriproxyfen water concentrations ranged from being equal to the daphnid LOEL to a level 13 times the LOEL.

    Following the second allowed application of Esteem® at the 16 oz/acre rate, a runoff event is predicted to result in model pond pyriproxyfen concentrations that exceed the daphnid chronic LOEL by 2.6 to 39 times. Labeled use of Esteem® is not likely to cause acute toxicity to fish or wildlife resources, however, the risk of significant freshwater aquatic invertebrate reproductive impairment is high.

    None of the materials submitted in support of registration of Esteem® establish how long of an exposure of adult aquatic invertebrates is needed to impede reproduction. However, in a discussion of the risks posed to freshwater invertebrates (reference USEPA Environmental Fate and Effects Division risk assessment for pyriproxyfen use on citrus, almonds and fruiting vegetables, dated 07/13/99), the reviewer reports that an analysis of the daphnia and mysid shrimp toxicity test results shows that the effects on reproduction for both species are likely to be occurring in the relatively short time period between egg fertilization and hatching. That is, with 4 to 9 days of exposure or less.

    The pyriproxyfen concentration predicted by AQUALIFE at the lowest runoff rate in one foot of water is three times the daphnia chronic LOEL following one Esteem® application at the lowest labeled pome fruit rate. As described previously, the fastest degradation pathway for pyriproxyfen in water is via photolysis with a half-life of approximately four days. Even under optimum photolytic conditions in the one foot depth model pond the pyriproxyfen concentration might remain above effective concentrations for 8 to 12 days. In deeper waters where degradation will occur by other slower degradation pathways it may persist far longer.

    The ecological effects review concluded that use of Esteem® on an agricultural scale will adversely impact aquatic invertebrate populations in waters near use sites and may produce indirect trophic effects on other aquatic species. In order to more effectively assess the impacts likely to be caused by the labeled use of Esteem®, Valent was granted the opportunity to submit any additional information that addressed the following areas:     By mutual agreement, the established registration decision date was waived to allow Valent to provide additional data and information which could affect the Department's current understanding of the impact of pyriproxyfen on aquatic organisms. The data package, received on September 14, 2000, was forwarded to the Department's Division of Fish, Wildlife & Marine Resources (DFW&MR).

    The following information prompted the DFW&MR to refine their initial risk assessment for Esteem®:

    Researchers at a California mosquito control research lab made pyriproxyfen applications directly to the surface of rice plots. The pyriproxyfen water column concentrations decreased by an average of roughly 11 fold per day before dropping below their method detection limit of 50 ng/L. In low application rate plots no measurable pyriproxyfen was present past day 1. In high rate plots none was detected after day 2. Dip, drag net, and trap samples yielded sufficient numbers in 14 of 23 invertebrate taxa to analyze statistically for treatment effects. Four groups were affected. Approximately 13 percent of newly emerged Odonate adults captured 4-10 days post application were deformed. Daphnoid cladocerans and ostracods experienced slightly depressed reproduction. Fourth-instar chironomids collected 5 hours after the second application and reared in the lab all died during the pupal-adult edysis. Chironomid larvae collected from control plots emerged normally. While the number of replicates for each treatment level is low, the mean number of chironomids drag netted in both the low and high dose plots recovered to levels above control means within 11 days after dosing, and remained higher through the end of the study. Additional sources from the literature and 2000 national Society of Environmental Toxicology and Chemistry (SETAC) conference presentations serve to characterize pyriproxyfen's effects on different species of invertebrates and at different concentrations.


    The Department's initial ecological effects risk assessment determined that use of Esteem®, as labeled, will adversely impact aquatic invertebrate populations in waters near use sites and may produce indirect trophic effects on other aquatic species. A combination of information submitted by Valent, a literature search, and recently completed work presented at the SETAC meeting has allowed for refinement of the initial risk assessment and mitigates concerns for major aquatic impacts. When used as labeled, Esteem® 0.86 EC Insect Growth Regulator should not cause unreasonable adverse effects to humans or the environment.


    The Department hereby accepts Esteem® 0.86 EC Insect Growth Regulator (EPA Reg. No. 59639-95) for registration in New York State. Enclosed for your files are the Certificate of Pesticide Registration and New York State stamped -'ACCEPTED' labeling (Form 1283-D).

    Please note that a proposal by Valent or any other registrant to register a product containing pyriproxyfen, whose labeled uses are likely to increase the potential for significant impact to humans, property or the environment, would constitute a major change in labeled (MCL) use pattern. Such an application must be accompanied by a new application fee and meet the requirements listed in Appendix 1.B. of "New York State Pesticide Product Registration Procedures" (August 1996).

    Please contact Frank Hegener, Chief of our Pesticide Product Registration Section, at (518) 457-7446, if you have any questions.


Maureen P. Serafini
Bureau of Pesticides Management


cc: w/enc. - N. Kim/D. Luttinger, NYS Dept. of Health
R. Zimmerman/R. Mungari, NYS Dept. of Ag. & Markets
G. Good/W. Smith, Cornell PMEP