Pesticide Toxicity Profile: Thiophthalimide Pesticides¹

Frederick M. Fishel²

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

General

There are currently only two members of the chemical family of thiophthalimide pesticides that remain on the market in the U.S. – captan and folpet. (A previous member, captafol, has been discontinued for use in the U.S.) Captan, one of the most widely used fungicides in the world, has many crops on its label, including fruits, nuts, and ornamentals, and is used for control of fungal and bacterial diseases. It also has application as a seed protectant. Practically every acre of Florida strawberries receives captan applications as well as approximately half of the U.S. apple acreage. The first commercially-available captan product entered the U.S. market in 1949. Current commercial formulations available include wettable powders, dusts, water dispersible granules, and flowables. There are also many products containing captan formulated especially for home garden use. There are limited numbers of uses for folpet in Florida, but it is labeled as a foliar treatment for control of scab on avocado. It is formulated as a wettable powder for this use. There are several commercial products of folpet in combination with bis(tributyltin) oxide. This combination is applied to wood products as a stain for prevention of damage caused by mildew and other wood decay organisms. Folpet first entered the market in 1962.

Toxicity

These fungicides may cause moderate irritation of the skin, respiratory tract, and eyes. Captan has a low acute toxicity and generally carries the signal word, CAUTION. It is not likely that captan would cause reproductive effects in humans at usual levels of exposure. Although the EPA concluded that captan does not produce birth defects or mutagenicity, they classify captan as a probable human carcinogen. Animal studies have shown that captan is rapidly metabolized and residues are excreted in the urine. Folpet is considered slightly toxic by ingestion. Long-term effects have varied in laboratory animals exposed to folpet. Mammalian toxicities for the thiophthalimide 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 some 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.meisterpro.com/modules.php?name=MP_Pages
Nesheim, O.N. 2002. Toxicity of pesticides. UF/IFAS EDIS Document PI-13. http://edis.ifas.ufl.edu/PI008.
Reigart, J.R. and J.R. Roberts. 1999. Recognition and management of pesticide poisonings, 5^th ed. United States Environmental Protection Agency Publication EPA-735-R-98-003.
Seyler, L.A., et.al. 1994. Extension toxicology network (EXTOXNET). Cornell University and Michigan State University. http://extoxnet.orst.edu/index.html. Visited July 2005.

Tables

Table 1.

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

Common name	Rat oral LD₅₀	Rabbit dermal LD₅₀
Captan	9,000	---
Folpet	>10,000	>5,000

Table 2.

Thiophthalimide pesticide wildlife toxicity ranges.

Common name	Bird acute oral LD₅₀(mg/kg)*	Fish (ppm)**	Bee^†
Captan	ST	HT	PNT
Folpet	ST	HT	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 thiophthalimide pesticides.

Common name	Trade names*	Chemical name
Captan	Captan®	N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide
Folpet	Folpet®	N-[(trichloromethyl)thio]phthalimide
*Does not include manufacturer's prepackaged mixtures.

Footnotes

This document is PI-63, one of a series of the Pesticide Information Office, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date September 2005. Reviewed: September 2008. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

Frederick M. Fishel, Associate Professor, Agronomy Department, and Director, Pesticide Information Office; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, 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 does 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 extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim Dean.