1991 – 1992: Darling River (NSW). Darling River sprayed with Algaecide to kill Blue Green-Algae.

…Terry Pearce received the results of the tests. Immediately Mitchell broadcast an emergency message on Bourke’s local radio station warning of the “extreme danger” to humans and stock: “we don’t want to alarm people… [but] the toxin from blue-green algae is, in fact, in pure form more dangerous than cyanide.” Mitchell then hatched a plan to spray vast tracts of the Darling with an agricultural algaecide. When the NSW Pollution Control Commission refused to grant permission for the aerial spraying, Mitchell said he would go ahead anyway, and the Commission warned they would sue him personally if he did. That wasn’t going to stop “the Mouth from Louth.”

Mitchell procured 600 litres of a copper-based algaecide. A large cotton irrigation firm offered to donate the use of one of their crop dusters and a pilot. When residents in Bourke heard of the shire’s plans for aerial spraying of the chemical over their water supply a group formed to try to halt the action. The chemical had never been used for this purpose and wasn’t approved for use on open water. Concerned residents called the Pollution Control Commission, which assured them the spraying would not go ahead. On 9 November Mitchell had the crop duster pilot track the ailing Darling over forty kilometres, releasing the deep blue liquid algaecide onto the water and black soil plains below. The pilot commented that “zigzagging along the ever-twisting Darling was an interesting change after the repetitious runs spraying cotton.”

The National Parks and Wildlife Service opposed the use of the chemical. Ian Smalls, the principal scientist of the Department of Water Resources, said if he’d known he would have strongly advised against its use. Copper-based algaecides work by attracting algae with its nutrient content. The algae absorb it through their cell wall and a digestive enzyme breaks down the algaecide and releases copper into the cell, killing the algae.

Thirsty weather: drought-stricken western New South Wales in 2007. Mark Merton

When used as directed, the algaecide is not toxic to humans. The reason so many authorities objected to its use – apart from its being untested in such circumstances – was that the algaecide causes the dead algae to release their neurotoxins into the water immediately. Smalls said the effect was “like putting pins in a balloon, releasing other materials.” According to the manufacturer’s website these toxins could persist for twenty-eight days. Authorities feared mass fish kills could result, as well as the potential for poisoning of stock and humans.

One Bourke resident wrote a letter to the Sydney Morning Herald asking if the Darling River was being “used as a guinea pig for experimenting with chemicals” and accusing Mitchell of using ten times the recommended concentration. Mitchell didn’t see his actions as a massive gamble. He claimed he had verbal permission from the Department of Agriculture in Orange and that the spraying had been a success. The department refuted this, telling the Herald, “We were waiting for Wally to get back to us to obtain official permission. He never did.”

For Wally Mitchell, a grazier himself, responsible for the safety of the shire’s people and its economically valuable stock, and getting nowhere with urban authorities, the dangers posed by a rapidly growing toxic algal bloom must have outweighed the risks of using the relatively benign algaecide. To some of the residents, however, it seemed as if some of the primary producers of the region had taken on the cavalier and reckless culture that they said the foreign-owned cotton firms had introduced.