{ "id": "epqhhhfnmt", "slug": "tridiphane", "title": "Tridiphane", "updated": "2026-10-21", "topic_path": [ { "id": "life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/topics/life" }, { "id": "life.production", "label": "Applied biology and nonhuman health", "api_url": "https://www.edgepedia.org/api/v1/topics/life.production" }, { "id": "life.production.plant_health", "label": "Plant disease and plant protection", "api_url": "https://www.edgepedia.org/api/v1/topics/life.production.plant_health" }, { "id": "life.production.plant_health.pesticides", "label": "Pesticides", "api_url": "https://www.edgepedia.org/api/v1/topics/life.production.plant_health.pesticides" }, { "id": "life.production.plant_health.herbicides", "label": "Herbicides", "api_url": "https://www.edgepedia.org/api/v1/topics/life.production.plant_health.herbicides" }, { "id": "life.production.plant_health.herbicides.chloroacetamide-and-chloroacetanilide-herbicides", "label": "Chloroacetamide and chloroacetanilide herbicides", "api_url": "https://www.edgepedia.org/api/v1/topics/life.production.plant_health.herbicides.chloroacetamide-and-chloroacetanilide-herbicides" } ], "geo": [ { "id": "geo.us.t1946.life.production.plant_health.herbicides", "label": "United States · 1946 to 2000: Herbicides", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life.production.plant_health.herbicides", "path": [ { "id": "geo.us", "label": "United States", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us" }, { "id": "geo.us.t1946", "label": "United States · 1946 to 2000", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946" }, { "id": "geo.us.t1946.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life" }, { "id": "geo.us.t1946.life.production", "label": "Applied biology and nonhuman health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life.production" }, { "id": "geo.us.t1946.life.production.plant_health", "label": "Plant disease and plant protection", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life.production.plant_health" }, { "id": "geo.us.t1946.life.production.plant_health.pesticides", "label": "Pesticides", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life.production.plant_health.pesticides" }, { "id": "geo.us.t1946.life.production.plant_health.herbicides", "label": "Herbicides", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t1946.life.production.plant_health.herbicides" } ] }, { "id": "geo.us.t2001.life.production.plant_health", "label": "United States · 2001 to 2020: Plant disease and plant protection", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t2001.life.production.plant_health", "path": [ { "id": "geo.us", "label": "United States", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us" }, { "id": "geo.us.t2001", "label": "United States · 2001 to 2020", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t2001" }, { "id": "geo.us.t2001.life", "label": "Life and health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t2001.life" }, { "id": "geo.us.t2001.life.production", "label": "Applied biology and nonhuman health", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t2001.life.production" }, { "id": "geo.us.t2001.life.production.plant_health", "label": "Plant disease and plant protection", "api_url": "https://www.edgepedia.org/api/v1/geo/geo.us.t2001.life.production.plant_health" } ] } ], "excerpt": "Tridiphane (nelpon, Dowco 356), CAS 58138-08-2, is an obsolete oxirane grass herbicide and synergist that inhibits glutathione S-transferases, boosting atrazine in corn; first reported 1981, withdrawn in the EU in 2002.", "snippet": "Tridiphane (nelpon, Dowco 356), CAS 58138-08-2, is an obsolete oxirane grass herbicide and synergist that inhibits glutathione S-transferases, boosting atrazine in corn; first reported 1981, withdrawn in the EU in 2002.", "node": "life.production.plant_health.herbicides.chloroacetamide-and-chloroacetanilide-herbicides", "markdown": "# Tridiphane\n\n**Tridiphane** (also known as nelpon or Dowco 356) is a synthetic oxirane (epoxide) herbicide, 2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane, that acts as a grass herbicide and, more importantly in practice, as a synergist that blocks the enzymatic detoxification of partner herbicides such as atrazine.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) • [2](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane) It was first reported in 1981, was withdrawn in the European Union in 2002, and is now considered obsolete, though it may remain available in some countries.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm)\n\n| Key fact | Detail |\n|---|---|\n| Chemical identity | (RS)-2-(3,5-dichlorophenyl)-2-(2,2,2-trichloroethyl)oxirane; CAS RN 58138-08-2; formula C₁₀H₇Cl₅O; molecular mass 320.43 Da[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n| Pesticide type | Herbicide and synergist; substance group: oxirane compound[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n| Mode of action | Enzyme inhibitor that inhibits meristematic activity; HRAC resistance class K3, WSSA class 15[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n| Synergism | Inhibits plant glutathione S-transferases, hindering rapid detoxification of partner herbicides, particularly atrazine, in post-emergent corn mixtures[2](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane) |\n| Key dates | First reported 1981; withdrawn in the EU 2002; GB and EC Regulation 1107/2009 status: not approved[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n| Example uses | Control of giant foxtail, crabgrass, and proso millet in cereals and corn[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n| Physical form | White solid, supplied as an emulsifiable concentrate; water solubility 1.8 mg/L at 20 °C, pH 7; log P 4.3[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) |\n\n## Chemistry\n\nTridiphane is a small-ring compound: a three-membered oxirane ring bearing a 3,5-dichlorophenyl group and a 2,2,2-trichloroethyl group on the same ring carbon.[3](https://patents.google.com/patent/EP0101168A2/en) The carbon of the oxirane ring is a chiral center, so the compound exists as (R)- and (S)-enantiomers, and commercial formulations are typically sold as racemic mixtures.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) Commercial synthesis is a multi-step organic process centered on constructing the oxirane ring and attaching the two substituents, with epoxidation as the final step.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) A related patent literature describes the same molecule as 1,1,1-trichloro-3,4-epoxy-3-(3,5-dichlorophenyl)butane and names it a preferred hydrophobic, hydrolyzable herbicide for controlled-release latex dispersion formulations, where it was used at about 75 to 95 percent by weight of the polymer solids.[4](https://patents.justia.com/patent/5260259)\n\n## Mode of action and synergism\n\nTridiphane's main value came from what it does to other herbicides. It is itself a highly active grass herbicide under pre-emergence conditions, but it found its most important application as a synergistic additive to atrazine or other herbicides in post-emergent corn herbicide mixtures.[2](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane) Its inhibition of glutathione S-transferases hinders the rapid detoxification of the partner herbicide by this enzyme, so the partner remains active longer in the weed.[2](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane)\n\nField and greenhouse work quantified the effect. A 1985 Weed Science study by Gail Ezra, Jack H. Dekker, and Gerald R. Stephenson, plant scientists at the [University of Guelph](https://www.edgepedia.org/university-of-guelph), found tridiphane to be a potent synergist of atrazine for postemergence control of giant foxtail (*Setaria faberi*) and large crabgrass (*Digitaria sanguinalis*).[5](https://www.cambridge.org/core/journals/weed-science/article/abs/tridiphane-as-a-synergist-for-herbicides-in-corn-zea-mays-and-proso-millet-panicum-miliaceum/E613478BBC56A09488612E0EDE1531C9) The same study found that alachlor, another herbicide detoxified via glutathione conjugation, was markedly synergized by tridiphane at both 2 and 4 kg ai/ha, resulting in 36 to 54 percent growth reduction compared with plants treated with the herbicides alone.[5](https://www.cambridge.org/core/journals/weed-science/article/abs/tridiphane-as-a-synergist-for-herbicides-in-corn-zea-mays-and-proso-millet-panicum-miliaceum/E613478BBC56A09488612E0EDE1531C9) A separate study of tridiphane and [metribuzin](https://www.edgepedia.org/metribuzin) in soybean and tomato found that tridiphane applied 1 or 4 hours before metribuzin caused the greatest phytotoxicity in metribuzin-sensitive soybeans, with increased uptake, increased translocation to the shoots, and decreased root metabolism of metribuzin explaining the interaction.[6](https://www.cambridge.org/core/journals/weed-science/article/abs/phytotoxic-interaction-of-tridiphane-and-metribuzin-in-metribuzin-sensitive-and-tolerant-soybean-glycine-max-and-tomato-lycopersicon-esculentum/E0BE4B526047A6EB491FD5ABECC2860D)\n\nTridiphane also affects mammalian drug-metabolizing enzymes. It has been shown to induce epoxide hydrolase, CYP enzymes (specifically CYP4A), and peroxisomal enzymes, and it functions as a selective CYP inhibitor, inhibiting CYP2B10 while having little or no effect on other CYP isoforms; in vitro it appears to be a competitive inhibitor of CYP, though its in vivo effect was not established in the reviewed work.[2](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane)\n\n## Uses in mixtures\n\nA 1983 European patent application by Schering Agrochemicals Ltd and FBC Ltd (inventors Anthony Joseph Mayes and Bryan Leslie Rea) claimed herbicidal mixtures of [benazolin](https://www.edgepedia.org/benazolin) with one of five partners, tridiphane among them, and specified that mixtures containing tridiphane could be used in cereals and maize.[3](https://patents.google.com/patent/EP0101168A2/en) In glasshouse tests described in that patent, aqueous suspensions of benazolin ethyl ester with tridiphane were sprayed on mayweed (*[Matricaria](https://www.edgepedia.org/matricaria)* spp.) with assessment 7 days after spraying, and synergism was exhibited.[3](https://patents.google.com/patent/EP0101168A2/en) Tridiphane was also compared with imazaquin, BAS 514, and fenoxaprop-ethyl for postemergence control of large crabgrass in turf, where BAS 514 and fenoxaprop-ethyl gave the best control.[7](https://www.cambridge.org/core/journals/weed-science/article/abs/postemergence-control-of-large-crabgrass-digitaria-sanguinalis-with-herbicides/72519311B953855AB345388B4F5D125E) An EPA emissions document for the pesticide application industry lists tridiphane as an active ingredient with no trade names listed.[8](https://www.epa.gov/sites/default/files/2020-10/documents/c9s02-2.pdf)\n\n## Regulatory status\n\nTridiphane is listed in the EU pesticides database but is not approved under EC Regulation 1107/2009, and its GB approval has expired with no UK approval for use as a plant protection agent.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) The Pesticide Properties Database classifies it as a Type II Highly Hazardous Pesticide on the bioaccumulation criterion, with a bioconcentration factor above 2000 L/kg, and notes it as a marine pollutant.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) It is not listed under the Rotterdam Convention or the Stockholm Convention, but is listed in Section B of the OSPAR list and under the EU Water Framework Directive.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) Tridiphane (CASRN 58138-08-2) has an IRIS entry maintained by the US EPA that includes a noncancer assessment and weight-of-evidence documents concerning cancer; however, via a Federal Register Notice issued in 2004, the EPA stated that pesticide chemicals would no longer undergo re-assessment under the IRIS Program.[9](https://iris.epa.gov/ChemicalLanding/%26substance_nmbr%3D0124)\n\n## Environmental fate and toxicology\n\nTridiphane is strongly sorbing and persistent enough to matter for aquatic exposure. Its soil degradation half-life (DT₅₀) is 28 days under unknown measurement conditions, classed as non-persistent, but its Koc of 5600 mL/g makes it non-mobile in soil, with a low GUS leaching index of 0.36 and a medium potential for particle-bound transport.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) Its log P of 4.3 and estimated bioconcentration factor of 5046 L/kg indicate a high potential to accumulate in organisms.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) [Acute toxicity](https://www.edgepedia.org/acute-toxicity) values include a rat oral LD₅₀ of 1740 mg/kg (moderate), a 96-hour rainbow trout (*Oncorhynchus mykiss*) LC₅₀ of 0.48 mg/L and a 48-hour *Daphnia magna* EC₅₀ of 0.22 mg/L (both moderate), and a bird acute LD₅₀ above 2510 mg/kg in mallard (*Anas platyrhynchos*), classed as low.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm) The database flags a high human-health alert for reproduction and development effects and warns that significant data are missing for both environmental fate and human health.[1](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm)\n\n## References\n\n1. [Tridiphane, Pesticide Properties DataBase (PPDB), University of Hertfordshire](https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/662.htm)\n2. [Tridiphane - an overview, ScienceDirect Topics](https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/tridiphane)\n3. [EP0101168A2 - Herbicidal mixtures, Google Patents](https://patents.google.com/patent/EP0101168A2/en)\n4. [US Patent 5,260,259 - Herbicidal latex dispersion for controlled delivery and release of herbicides, Justia Patents](https://patents.justia.com/patent/5260259)\n5. [Ezra, G., Dekker, J. H., Stephenson, G. R. (1985). Tridiphane as a Synergist for Herbicides in Corn (Zea mays) and Proso Millet (Panicum miliaceum). Weed Science 33(3)](https://www.cambridge.org/core/journals/weed-science/article/abs/tridiphane-as-a-synergist-for-herbicides-in-corn-zea-mays-and-proso-millet-panicum-miliaceum/E613478BBC56A09488612E0EDE1531C9)\n6. [Phytotoxic Interaction of Tridiphane and Metribuzin in Metribuzin Sensitive and Tolerant Soybean and Tomato, Weed Science](https://www.cambridge.org/core/journals/weed-science/article/abs/phytotoxic-interaction-of-tridiphane-and-metribuzin-in-metribuzin-sensitive-and-tolerant-soybean-glycine-max-and-tomato-lycopersicon-esculentum/E0BE4B526047A6EB491FD5ABECC2860D)\n7. [Postemergence Control of Large Crabgrass (Digitaria sanguinalis) with Herbicides, Weed Science](https://www.cambridge.org/core/journals/weed-science/article/abs/postemergence-control-of-large-crabgrass-digitaria-sanguinalis-with-herbicides/72519311B953855AB345388B4F5D125E)\n8. [AP-42, CH 9.2.2: Pesticide Application, US EPA](https://www.epa.gov/sites/default/files/2020-10/documents/c9s02-2.pdf)\n9. [Tridiphane, CASRN 58138-08-2, IRIS, US EPA ORD](https://iris.epa.gov/ChemicalLanding/%26substance_nmbr%3D0124)\n\n---\n*Topic: Encyclopedia › Life and health › Applied biology and nonhuman health › Plant disease and plant protection › Pesticides › Herbicides › Chloroacetamide and chloroacetanilide herbicides*\n\n*Initially written Oct 21, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n", "same_as": [], "url": "https://www.edgepedia.org/tridiphane", "markdown_url": "https://www.edgepedia.org/tridiphane.md", "license": { "name": "Edgepedia Community License 1.0", "url": "https://www.edgepedia.org/edgepedia/license", "summary": "Free with credit, commercial use included. AI training is open to everyone. For other uses, organizations over USD 100M in revenue or 100M monthly users license separately.", "spdx": "LicenseRef-Edgepedia-Community-1.0" }, "credit": "\"Tridiphane\", Edgepedia (EdgeChat), https://www.edgepedia.org/tridiphane. Edgepedia Community License 1.0.", "credit_md": "\"[Tridiphane](https://www.edgepedia.org/tridiphane)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/tridiphane](https://www.edgepedia.org/tridiphane). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).", "credit_html": "\"Tridiphane\", Edgepedia (EdgeChat), https://www.edgepedia.org/tridiphane. Edgepedia Community License 1.0.", "speakable": "Tridiphane, CAS 58138-08-2, is an obsolete oxirane grass herbicide and synergist that inhibits glutathione S-transferases, boosting atrazine in corn; first reported 1981, withdrawn in the EU in 2002." }