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Publication #PI-67

Pesticide Toxicity Profile: Strobilurin Pesticides1

Frederick M. Fishel2

This document provides a general overview of human toxicity, a listing of laboratory animal and wildlife toxicities, and a cross-reference of chemical, common, and trade names of the strobilurin pesticides registered for use in Florida.

General

The strobilurin pesticides are a group of relatively new fungicides, with azoxystrobin receiving EPA registration in 1997. Trifloxystrobin followed in 1999 and, most recently, pyraclostrobin received registration. They are effective against several important plant pathogens, but also have some unique properties. They are the first family of fungicides to provide control of all three major types of plant pathogenic fungi and because of their strong affinity for plant waxes, they are capable of translocating from the upper leaf surface to the lower, providing control on both surfaces. The strobilurins have a wide range of sites where they may be applied and dependent upon product, they are registered for use on citrus, small and tree fruits, turfgrass, field and vegetable crops, and many specialty commodities. Soon after they were released, resistance was first reported with certain fungi in Asia and Europe, and this has since occurred in North America. Because the strobilurins have a very site-specific mode of action (mitochondrial respiration inhibition resulting in prevention of spore germination and mycelial growth), they have a relatively high resistance risk. Strobilurin products pre-packaged with fungicides having different modes of action, including chlorothalonil, propiconazole, fludioxonil, or mefenoxam are commercially available. Product formulations of the strobilurins include dry flowables or water dispersible granules, emulsifiable concentrates, and liquid flowables.

Toxicity

The strobilurin pesticides are regarded as a family of relatively safe pesticides in terms of acute, chronic, and long-term effects. With acute oral, dermal, and inhalation effects, they are classified Category III and carry the signal word CAUTION on their labels. In other terms, this translates into the following quantities that would be expected to cause acute toxicity to a 150-pound person: oral ingestion of 500 to 5,000 mg/kg body weight, dermal exposure of 2,000 to 20,000 mg/kg body weight, or inhalation of 2.0 to 20.0 mg/l. The acute oral ingestion would equate to one ounce to one pint as the lethal dose. They are considered to be non-oncogenic in rat chronic toxicity studies. There were no reports of reproductive, teratogenic, developmental or carcinogenic effects; they are quickly metabolized and excreted. The strobilurins are toxic to fish and aquatic invertebrates. Their product labels have statements regarding use precautions around water and areas of groundwater concern. Other ecological effects appear to be negligible. Mammalian toxicities for the strobilurin pesticides are shown in Table 1. Table 2 lists the toxicities to wildlife by the common name of the pesticide. Table 3 provides a cross-listing of many of the trade names that these products are registered and sold by in Florida.

Additional Information

Crop Protection Handbook. 2005. vol. 91. Willoughby, Ohio: Meister Publishing Co. http://www.meistermedia.com/publications/handbook.html.

Nesheim, O.N., Frederick M. Fishel, and Mark Mossler. 2002. Toxicity of pesticides. UF/IFAS EDIS Document PI-13. http://edis.ifas.ufl.edu/pi008.

Seyler, L.A., et.al. 1994. Extension toxicology network (EXTOXNET). Cornell University and Michigan State University. http://extoxnet.orst.edu/index.html.

Tables

Table 1. 

Strobilurin pesticide mammalian toxicities (mg/kg of body weight).

Common name

Rat oral LD50

Rabbit dermal LD50

Azoxystrobin

>5,000

>2,000 (rat)

Kresoxim-methyl

>5,000

>2,000 (rat)

Pyraclostrobin

>500–>2,000

>4,000 (rat)

Trifloxystrobin

>4,000

>2,000

Table 2. 

Strobilurin pesticide wildlife toxicity ranges.

Common name

Bird acute oral LD50 (mg/kg)*

Fish (ppm)**

Bee

Azoxystrobin

PNT

HT

PNT

Kresoxim-methyl

57

MT

---

Pyraclostrobin

ST–PNT

HT

PNT

Trifloxystrobin

ST–PNT

HT–VHT

PNT

* Bird LD50: Practically nontoxic (PNT) = >2,000; slightly toxic (ST) = 501 – 2,000; moderately toxic (MT) = 51 – 500; highly toxic (HT) = 10 – 50; very highly toxic (VHT) = <10.

** Fish LC50: PNT = >100; ST = 10 – 100; MT = 1 – 10; HT = 0.1 – 1; VHT = <0.1.

Bee: HT = highly toxic (kills upon contact as well as residues); MT = moderately toxic (kills if applied over bees); PNT = relatively nontoxic (relatively few precautions necessary).

Table 3. 

Cross-reference list of common, trade, and chemical names of strobilurin pesticides.

Common name

Trade names*

Chemical name

Azoxystrobin

Abound®, Amistar®, Dynasty®, Heritage®, Quadris®

Methyl (E)-2-2-6-(cyanophenoxy)pyrimidin-4-yloxy-phenyl-3-methoxyacrylate

Kresoxim-methyl

Sovran®

Methyl (E)-2-methoxylimino-2(2-(o-toloxymethyl) phenyl) acetate

Pyraclostrobin

Cabrio®, Headline®

Carbamic acid [2-[[[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxy]methyl]phenyl]methoxy-, methyl ester

Trifloxystrobin

Flint®, Gem®, Compass®

Benzeneacetic acid, (E,E)-alpha-(methoxyimino)-2-((((1-(3-trifluororomethyl)phenyl)ethylidene)amino)oxy)methyl)-methyl ester

* Does not include manufacturers' prepackaged mixtures.

Footnotes

1.

This document is PI-67, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date September 2005. Revised September 2012. Reviewed September 2015. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Frederick M. Fishel, professor, Agronomy Department, and director, Pesticide Information Office; UF/IFAS Extension, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.