Triphenyltin hydroxide

Pesticide Type Fungicide (Group 30)
Chemical Class organotin
Common Trade Names* Super Tin®,Agri Tin®
Registration Status EPA: Registered since 1971
MN: Registered

Diagram of the chemical structure for triphenyltin hydroxide.

*No endorsement is implied in the referencing of trade names


Triphenyltin hydroxide (TPTH), also known as fentin hydroxide, is a non-systemic foliar fungicide used to control early and late blight on potatoes, leaf spot on sugar beets, and select fungal diseases on pecans. TPTH also exhibits anti-feeding properties for some surface-feeding insects (e.g., Colorado potato beetle). It is a restricted use pesticide (RUP) and is only registered for use on these three crops. There are no residential, public health, or other non-food uses of TPTH. In 2017, over 200,000 pounds of this active ingredient were sold in Minnesota.1

Mode of Action

TPTH inhibits oxidative phosphorylation (respiration) and fungal growth. It is a Fungicide Resistance Action Committee (FRAC) code 30 fungicide which inhibits adenosine triphosphate (ATP) synthase preventing the production of ATP by cell mitochondria.

Issues with Resistance

Cercospora leaf spot is a serious leaf disease of sugar beets in the north Great Plains. In 1994, testing of Cercospora leaf spot from sugar beet fields in North Dakota and Minnesota revealed tolerance to TPTH.2

Triphenyltin hydroxide Movement in the Environment

TPTH has low solubility in water and binds strongly to soil. Therefore, it is not expected to leach to groundwater; however, it may reach surface water through spray drift and surface run-off.3 To protect nontarget organisms, product labels include application setbacks from surface waters such as rivers, streams, ponds, and lakes of 100 feet for ground boom sprayers and 300 feet for aerial applications.4 TPTH is semi-volatile from dry surfaces but non-volatile from water. The aerobic soil half-life of TPTH is greater than 1,114 days.3

Detection in Minnesota Waters

The MDA does not currently test for TPTH in Minnesota groundwater and surface water samples. Analysis for this chemical cannot be incorporated into the existing procedures used by the MDA laboratory and would require additional analytical methods or laboratory equipment. Monitoring conducted in the state by the US Geological Survey (USGS) between 2012 and 2019 has not detected TPTH in Minnesota groundwater or surface water samples. TPTH has been detected in surface water samples from other upper Midwest states including Iowa (one sample at 3.8 ppt) and North Dakota (one sample at 6.1 ppt).5 The overall detection frequency in surface waters in the US has been low, less than <1% of surface water samples.

Triphenyltin hydroxide and Non-target Organisms

TPTH is very highly toxic to fish and aquatic invertebrates on an acute exposure basis. The Environmental Protection Agency (EPA) Office of Pesticide Programs aquatic life benchmarks are 3550 and 65 ppt for acute and chronic exposure, respectively.3 EPA categorizes TPTH as moderately toxic to birds and mammals from acute oral exposure (mallard duck LD50 = 378 mg ai/kg; Norway rat LD50 = 156 mg ai/kg). Some vascular plants are also sensitive to high rates of this fungicide. It is considered practically nontoxic to bees on an acute contact basis.6

Triphenyltin hydroxide and Human Health

TPTH has high acute toxicity by oral, dermal, and inhalation routes. The EPA categorizes pesticide toxicity to human using a scale that ranges from I (most toxic) to IV (least toxic). The acute oral, dermal irritation, inhalation, and eye irritation categories for TPTH are II, II, I, and I, respectively.  TPTH is classified as a probable human carcinogen.7

The primary routes of human exposure are through dermal contact and inhalation. The greatest risk is for pesticide applicators and handlers. In occupational settings, humans may be exposed to TPTH during handling and application as well as post-application for workers entering treated fields. Fields treated with TPTH have a 48-hour restricted entry interval for agricultural worker protection.6,7 Humans can also be exposed to TPTH through food and drinking water. Exposure in residential settings is considered unlikely as there are no residential uses of TPTH.7

TPTH pesticides carry a “DANGER” signal word and direct mixers/loaders/applicators to wear personal protective equipment including chemical resistant coveralls/clothing, gloves, boots, respirator with organic vapor cartridges, and goggles/face shield.4

Updated October 2020

1Minnesota Department of Agriculture. 2017. Pesticide Sales Database. Accessed May 13, 2020.

2G Secor, V Rivera, M Bolton. 2020. Sensitivity of Cercospera beicola to foliar fungicides in 2019. Sugarbeet Research and Extension Reports 50:170-177.

3US Environmental Protection Agency. 2018. Registration Review: Preliminary Environmental Fate and Ecological Risk Assessment for Triphenyltin Hydroxide (TPTH; Fentin Hydroxide). EPA-HQ-OPP-2012-0413-0016.

4US Environmental Protection Agency. 11/1999. Reregistration eligibility decision FACTS, Triphenyltin Hydroxide. EPA-738-F-99-014.

5US Environmental Protections Agency. 2019. Office of Pesticide Programs aquatic life benchmarks and ecological risk assessments for registered pesticides.

6US Environmental Protection Agency, 2018. Human Health Draft Registration Review Risk Assessment for Triphenyltin Hydroxide (TPTH) (EPA-HQ-OPP-2012-0413-0018). Accessed May 1, 2020.

7US Environmental Protection Agency. 2000. Triphenyltin Hydroxide; Proposed Determination to Terminate Special Review; Notice. Federal Register 65:204.