The smell was unmistakable as Chelsea Woolston drew up at the family farm, 6000 acres of grazing land hemmed in by the spectacular sandstone cliffs of the Grampian Ranges.

"I'd say 'Mum, you've been spraying again' and she'd say 'yes, yes I have'," Ms Woolston recalled.

Bernie Dunn believed it was the responsibility of all people to try to make a difference – no matter how small – to the wellbeing of humanity and the world around them.

"She sprayed Roundup excessively by hand … spraying the garden out, all the edges, around the laneways and around the shearing sheds."

At the age of 63, Dot Dunn was vigorously healthy, shouldering her share of the physical labour at the farm in western Victoria where she lived with her husband Bernie.