Azoxystrobin in the Environment

ENVIROfacts Syngenta Crop Protection

AZOXYSTROBIN

The Active Ingredient in Quadris and Abound One of the Active Ingredients in Quilt®

Chemical Structure: Chemical Nomenclature:

Methyl (E)-2-{2[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3- N N methoxyacrylate (IUPAC) O O CAS No.: 131860-33-8 Use: Broad Spectrum fungicide CN CH O OCH 3 3

Molecular Formula: C22H17N3O5 Physical Properties: State: Pale brown crystalline powder Molecular Weight: 403.4 Melting Point: 116°C Sp. Gravity: 1.34 g/cm3 Physicochemical Chemical Stability: Properties: Aq. Photolysis (t1/2): ca. 14 days in pure sterile water 6.7 mg/L and 3 days in natural river water Aq. Solubility: 2.5 -10 Log Kow 1.1x10 Pa at 20°C Aq. Hydrolysis (t1/2): Stable at environmental pH and Vapor Pres.: (8.2x 10-13 mm Hg) temperature 7.3 10-9 Pa m3 mol-1 Henry’s Law Constant: Neither acidic nor basic Volatility: Not volatile from soil or plant Dissociation constant (pKa) properties surfaces Environmental Fate Profile: Ecotoxicological Profile: Birds: practically nontoxic Lab metabolism half-life : 57 -136 days oral LD50 >2000 mg /kg dietary LC50 >5200 ppm as Lab soil photolysis half-life : 11 days Bees and other non-target practically nontoxic Field Soil Half-life: average 14 days arthropods: contact LD50 >200 µg /bee harmless to non-target Koc : 300 -1690 arthropods

Mobility Classification - low mobility to immobile Earthworms LC50 284 mg/kg soil

Sediment/water dissipation unavailable Fish: highly to moderately toxic rate (DT50) : acute LC50 = 470 - 2160 µg/L

Aquatic Invertebrates: very highly to moderately toxic acute EC50 = 55 - >4000 µg/L

Aquatic Plants/Algae: EC50 = 57 – 10000 µg/L

Application Rates: Margin of Safety (Environmental Risk):

Applied at 5.0 to 24.6 fl oz (product) per acre (0.08 to 0.4 lb. Azoxystrobin is of low toxicity and consequently low risk to birds, active ingredient per acre) depending on crop and/or target mammals, bees and other non-target terrestrial organisms. disease. Applied as a foliar spray or as soil spray at planting. Although highly toxic to aquatic organisms, actual field use of Also applied as Protégé seed treatment at 0.1 to 3.75 fl oz azoxystrobin results in a low risk of effects due to azoxystrobin’s (product) per 100 lb. seed (0.65 to 24.3 g. active ingredient low application rates and dissipation rate in the environment. per 100 kg. seed) depending on crop and/or target disease.

ENVIRONMENTAL OVERVIEW

The safety of a chemical in the environment and any potential risk to non-target plants and animals is a function of its toxicity (hazard) and also exposure. Low or no exposure of non-target organisms limits the potential for toxicological effects in the environment. The level and duration of exposure is determined by the application rates and the fate and transport of the chemical in the environment.

In the terrestrial environment azoxystrobin is rapidly dissipated. Soil photolysis (breakdown by sunlight) and microbial degradation are both important degradation mechanisms for azoxystrobin. The resulting breakdown products (degradates, metabolites) of azoxystrobin are themselves readily degraded and thus are only present at low levels and do not accumulate in soil. They are ultimately mineralized to carbon dioxide. Azoxystrobin and its breakdown products do not leach to groundwater due to a combination of their degradation rates and relatively low mobility in soil. The biological activity of each of the major degradates of azoxystrobin has been evaluated. These tests show that there are no toxicological or ecotoxicological concerns with these compounds. Based on These findings and the limited exposure the risk assessment needs to focus on the parent substance, azoxystrobin. Toxicity studies show that azoxystrobin is of low toxicity to terrestrial organisms, including birds, mammals, bees and other insects, and earthworms. Based on a combination of low exposure and toxicity it can be concluded that azoxystrobin will not present an unacceptable risk to the terrestrial environment.

In the aquatic environment, exposure will be limited by the physical and chemical properties of azoxystrobin, which will result in low exposure via run off. Once in water bodies, azoxystrobin will be dissipated by adsorption to sediment and subsequent microbial degradation. These factors along with low application rates mean that exposure of non-target species in aquatic environments will be low. Laboratory studies show that azoxystrobin is toxic to aquatic organisms. However, risk assessments show that risk to aquatic organisms and the aquatic environment is low.

COMMON QUESTIONS AND ANSWERS

Q. From an environmental perspective why was azoxystrobin categorized as a reduced risk pesticide by the US Environmental Protection Agency (EPA)?

A. Syngenta proposed azoxystrobin as a reduced risk pesticide due to its very favorable environmental and toxicological profile combined with low use rates.

Q. Can azoxystrobin move off-target after application?

A. Yes. As with any agricultural pesticide, off-target movement is possible following use of azoxystrobin. Results from field studies and simulation modeling for azoxystrobin indicate that leaching will be insignificant and run-off will be low. As with all pesticides, spray drift can potentially occur with azoxystrobin and measures should be employed to minimize drift (see product label). Risk assessments have shown that potential concentrations of azoxystrobin in surface waters which could result from run-off and drift will not present an unacceptable risk to aquatic organisms.

Q. Where is azoxystrobin located after application? Does it bind to plant foliage or soil?

A. After foliar application some of the azoxystrobin is taken up by plant leaves and it shows some movement within the plant. Any azoxystrobin which reaches the soil either directly during application or by wash-off is bound by soil organic matter and movement in soil is limited.

Q. What happens to azoxystrobin following rainfall? Does it wash off the plant foliage? When runoff from the field occurs following heavy rainfall, does azoxystrobin move with the soil or water in the runoff?

A. Some azoxystrobin will remain within the leaf and on the leaf surface, however some will also be washed off. In a run-off event azoxystrobin will move with both the soil and water in the run-off. The proportion adsorbed will depend on the relative amounts of soil and water in the run-off, although based on its soil adsorption coefficient most will be in the water phase.

Q. Is azoxystrobin degraded in the environment after application? What is the method of degradation ?

A. Yes. In soil azoxystrobin is degraded by soil surface photolysis (sunlight induced breakdown) and by microbes. Both processes result ultimately in the complete mineralization of azoxystrobin to carbon dioxide. Based on an extensive set of field studies it can be concluded that persistence of azoxystrobin in soil is not directly correlated with soil properties such as pH or organic matter. However studies indicate that degradation rates in soil increase with soil microbial activity. Soil surface degradation rates of azoxystrobin also increase with both sunlight intensity and day length.

In plants, azoxystrobin is degraded on the leaf surface by photolysis and is also taken up by the plant and broken down. The degradation products of azoxystrobin in and on plants are of no toxicological concern and have no significant fungicidal activity.

Q. How is azoxystrobin degraded in water if it enters water bodies?

A. In water, azoxystrobin dissipates rapidly due mainly to adsorption to sediment. In clear shallow water bodies, photolysis could also be an important route of dissipation. Once azoxystrobin is adsorbed to sediment it is microbially degraded to an acid metabolite (Compound 2), which is of no concern with respect to either man or to the environment and which is not fungicidally active.

Q. What happens to azoxystrobin in saltwater? Could it affect saltwater organisms?

A. The fate of azoxystrobin will follow the same pathways in salt or freshwater environments. Studies with saltwater organisms show they respond to azoxystrobin in the same way as freshwater organisms and have similar sensitivities.

Q. Can azoxystrobin accumulate in the sediment of water bodies and have an adverse effect on aquatic life?

A. In aquatic environments the major initial route of dissipation is by adsorption to bottom sediments where it is ultimately degraded. The potential for accumulation in sediments is low. Long-term toxicity studies with sediment-dwelling organisms have shown a huge margin of safety between potential environmental concentrations and concentrations that cause a toxic effect.

Q. Are azoxystrobin breakdown products harmful to the environment ?

A. No. The metabolites and photoproducts of azoxystrobin have been evaluated for their potential to present a risk to the environment. The results of these studies show that the degradates are all much less toxic (approximately 1000 X) to aquatic organisms than azoxystrobin.

Q. Is azoxystrobin mobile in the soil and can its use result in groundwater contamination?

A. Following an international program of field soil dissipation trials (designed to test for leaching potential) there have been no cases where azoxystrobin has been found to be mobile in soil. These studies are often carried out under “worst case” conditions with maximum use rates and high levels of irrigation. In addition, results of worst-case laboratory leaching studies show that azoxystrobin does not leach. Given this, there is no risk of azoxystrobin resulting in groundwater contamination.

Q. Will azoxystrobin accumulate in the environment or in non-target organisms?

A. No. Azoxystrobin is degraded in plants, soil and water and therefore will not accumulate in the environment. Based on its moderate lipophilicity azoxystrobin will not accumulate in non-target organisms. This is supported by data on metabolism and excretion in mammals, which shows rapid elimination of azoxystrobin via excreta and very low residues in tissues.

Q. Why do labels for azoxystrobin indicate that azoxystrobin is toxic to freshwater and estuarine/marine fish and aquatic invertebrates while some other fungicide labels do not? Is azoxystrobin toxic to fish, shrimp, and other aquatic organisms?

A. These statements are based on labeling requirements for environmental hazard, based on the laboratory acute toxicity tests. The statements do not indicate environmental risk from actual use of azoxystrobin. Risk is a function of both toxicity and exposure. The toxicity of azoxystrobin to fish, shrimp, and other aquatic organisms means it is categorized as very highly toxic. However, exposure of aquatic organisms to azoxystrobin is low and standard risk assessment procedures demonstrate that azoxystrobin presents low risk to all aquatic organisms.

Q. How safe is azoxystrobin to birds, insects, earthworms, and other animals?

A. Azoxystrobin has an excellent ecotoxicological profile. The toxicity of azoxystrobin to birds, insects, earthworms, and other animals is low and this combined with low use rates means that azoxystrobin presents negligible risk to these organisms.

Q. What Best Management Practices (BMPS) should an applicator and/or grower adopt when using pesticides like azoxystrobin?

A. In areas where extreme weather conditions (severe rainfall events) can be expected and where fields are located near rivers or streams, growers are encouraged to practice land management to limit runoff of soil and water from the field. This can be accomplished through the use of such practices as contour farming, terraces, and buffers.

Q. How can a grower use azoxystrobin in a manner that is consistent with sustainable agriculture practices (IPM, ICM, resistance management, etc)?

A. As with all products, growers should utilize azoxystrobin wisely, as one component of an Integrated Pest Management (IPM) and Integrated Crop Management (ICM) system. Be attentive to proper calibration, coverage, and timing. Implement drift avoidance measures listed on the label. Follow the specific resistance management directions for each crop concerning number of applications, rotation to other products, and spray intervals. All of these practices will help to ensure the continued effectiveness of azoxystrobin in IPM and ICM programs.

Important: Always read and follow label instructions before buying or using these products.

Syngenta Crop Protection, Inc. warrants that its products conform to the chemical description set forth on the products’ labels. NO OTHER WARRANTIES, WHETHER EXPRESS OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY AND OF FITNESS FOR A PARTICULAR PURPOSE, SHALL APPLY TO SYNGENTA’S PRODUCTS. Syngenta Crop Protection, Inc. neither assumes nor authorizes any representative or other person to assume for it any obligation or liability other than such as is expressly set forth herein. UNDER NO CIRCUMSTANCES SHALL SYNGENTA CROP PROTECTION, INC. BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR HANDLING OF ITS PRODUCTS. No statements or recommendations contained herein are to be construed as inducements to infringe any relevant patent now or hereafter in existence.

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