Banned Fungicide Detected Hundreds of Times in Victorian Drinking Water Supplies

Key Facts:

Benomyl banned in Australia in 2006

Benomyl detected 141 times in Victorian water supplies between 2017 and 2026.

Benomyl was sixth most frequently detected pesticide in Victorian water supplies between 2017 and 2026.

Benomyl can rapidly degrade into the fungicide Carbendazim.

Benomyl detections averaged 0.03% of Australian drinking water guidelines.

The most detections were at Quambatook (15), Lake Fyans (9), St. Arnaud (9), Tullaroop Reservoir (9), Centenary Reservoir (8).

Benomyl was detected by Central Highlands Water, Grampians Wimmera Mallee Water, Lower Murray Water and North East Water.

A fungicide, banned by the Australian pesticide regulator 20 years ago has been detected in drinking water supplies across northern Victoria over the past decade. Benomyl was banned by the federal pesticide regulator in 2006. It had been marketed under the trade name Benlate and manufactured by notorious company DuPont. Benlate had been surrounded in controversy including a class action undertaken in Australia due to widespread crop damage.

Legal action by 1900 farmers against Dupont also occurred in the United States, Puerto Rico and Costa Rica in the early 1990’s regarding widespread crop damage costing DuPont almost $1billion. The fungicide was also linked to a boy born blind (micropthalmia) in Florida after his mother claimed she had been exposed to the chemical when pregnant. Similar cases had apparently been reported in England. In 2008 DuPont paid confidential settlements to two New Zealand families whose families were born with birth defects.

Cross contamination of Benlate with the herbicide Atrazine was also the result of legal action in the United States in 1989. In 2001 a jury decision in Florida found DuPont liable for racketeering, negligence, fraud and defective product.

Benomyl was used in fruit, nut, vegetables and field crops and is toxic to soil microorganisms and invertebrates, particularly earthworms. Benomyl can also be highly toxic to aquatic organisms including fish. It breaks down into a closely related chemical called Carbendazim which can also be highly toxic to fish. In tests carried out over 2020-2021 in the Richmond River catchment in NSW, researchers also detected Benomyl. Marine scientist Kirsten Benkendorff was reported in the ABC in December 2023 saying in regards to Benomyl “It is a really big concern to have found a banned pesticide in our water here — we don’t know who is using it or why,” she said. “It’s a pesticide with a pretty short half-life, so it’s not something that has been hanging around in the environment for a long time.”

The information regarding Benomyl in Victorian drinking water supplies was gained through multiple Freedom of Information requests to Victorian Water Authorities. The FoI’s covered the years 2017 through to 2025. Similar FoI’s requested back in 2016 revealed 9 detections of Benomyl.

Friends of the Earth Land Use Researcher Anthony Amis said:

“From almost 2000 pesticide detections detected by water authorities across Victoria, Benomyl was the sixth most frequently detected pesticide with 141 detections in 43 different water supplies. Five separate water authorities reported Benomyl. How on earth is this fungicide still being detected 20 years after it was banned in Australia? It’s half life can be about one year, but that doesn’t fully explain all the detections occurring 15 to 20 years after it was banned. It could also be possible that a closely related chemical was detected, and listed as Benomyl by laboratories assessing the water samples.

If Benomyl was detected as the results suggest, the fungicide could have been stockpiled on farms or farmers were accessing the chemical through other means, probably online sales. The Federal pesticide regulator, the APVMA announced in February 2025 that it had removed 532 unregistered products from online stores in 2024. Was Benomyl/Benlate among products that were removed?” Six Benomyl detections have occurred since the APVMA made that announcement in early 2025.

“It’s clear that a toxic fungicide has been used across a large swathe of northern Victoria, polluting water supplies, with the peak amount of detections occurring between 2019 and 2022. If it’s been detected in water supplies, which cover a smaller amount of land in Victoria than other farmland, widespread pollution must have occurred outside of water supplies as well. What has been the ecological impact of this pollution?” Mr Amis said.

Benomyl detections may also have been a result of spray drift as Benomyl was also detected in water from Lake Wartook in the Grampians. There is no agriculture within the Lake Wartook catchment so the chemical must have been blown in by spray drift or fell with rain. Benomyl was also detected in water supplies along the Murray River in the north west, north east Victoria and also in water supplies in the Grampians and Wimmera areas.

Benomyl does not have an ecological guideline in Australia, meaning quantifying potential ecological impacts are extremely difficult. Benomyl also supposedly breaks down into Carbendazim very soon after it is applied in plants, soils or aquatic environments. Carbendazim is the major environmental degradant of Benomyl and also the fungicides Thiabendazole and Thiophanate-Methyl. Can the Benomyl detections actually be cross-reactivity to a structurally similar chemical?

In Australia there are currently 35 products that have Carbendazim as an active constituent. 18 products have Thiabendazole as an active constituent, with an additional 8 products containing Thiophanate-Methyl. The five separate water authorities that detected Benomyl did not test for Carbendazim, Thiabendazole or Thiophanate Methyl. Carbendazim has an Australian drinking water guideline, the same as Benomyl of 90µg/L (parts per billion).

There are no ecological guidelines for Carbendazim in Australia, but a proposed ecotoxicity threshold value for Carbendazim in Queensland has been suggested at 0.029µg/L (99%) and 0.45µg/L (95%). About one quarter of Benomyl detections were >0.029µg/L.

All Benomyl detections were in raw water that had not been treated and in some cases the detections were in large Reservoirs. The risks to drinking water would be lessened due to water treatment processes such as Powder Activated Carbon which can greatly reduce the amount of chemical in the reticulated water supply. The Australian Drinking Water Guidelines grant Benomyl a guideline of 90µg/L. Average amounts of Benomyl were 0.03µg/L (parts per billion) and about 0.03% of the Australian drinking water guidelines.

The highest amount of Benomyl detected in a water supply was 0.26µg/L in Tullaroop Reservoir north of Ballarat. Tullaroop is part of the Maryborough drinking water supply. Maryborough’s drinking water supply (Centenary Reservoir) recorded 8 Benomyl detections between 2017 and 2024 averaging 0.028µg/L. A small farm channel south of Shepparton (outside of a domestic water supply) recorded the states highest Benomyl detection of 0.54µg/L. This site was apparently the location of a mass yabby poisoning event in 2022.

In terms of Benomyl ‘hotspots’ the water supply with the most detections was at Quambatook in the states north west. Quambatook recorded 15 detections of Benomyl between 2018 and 2026 averaging 0.043µg/L. Quambatook water treatment plant uses Granular Activated Carbon which will significantly reduce levels of Benomyl post treatment. Other Benomyl hotspots were Lake Fyans (east of the Grampians) and St.Arnauds 1000ML storage which both recorded 9 detections.

The St.Arnuads detections could mean Benomyl contamination of the Grampians Wimmera water supply. Tullaroop Reservoir recorded 9 detections, with Centenary Reservoir near Maryborough recording 8 detections. There were also a large number of detections in North East Victoria, including 7 detections at Freeburgh storage near Bright and 5 detections at Nil Gully Myrtleford.