Mouse plague hits WA grain farmers as numbers surge in SA: ‘You literally can’t get away from them’

Grain growers are on high alert as mouse numbers in Western Australia reach plague proportions and numbers surge in South Australia.

Steve Henry, who researches mice and their impact on the grain industry at CSIRO, says more than 800 mice per hectare is considered a plague.

“In Western Australia we’re now using the P word,” he said. “We’re getting reports out of Western Australia of 3,000 or 4,000 burrows per hectare.”

“That’s real cause for concern. It’s a plague under any circumstances.”

Areas around Geraldton – about 400km north of Perth – were most affected, with similar reports coming in from southern parts of the WA wheatbelt.

On the Adelaide plains, mouse numbers were already “extremely high” and “very concerning for farmers”, Henry said.

The 2020-21 plague that occurred in eastern Australia caused an estimated $1bn damage. It exposed people and their pets to pesticides and disease, increased stress, and affected the health of livestock (due to contamination of feed and water with mouse urine and carcasses).

The current situation could rapidly escalate. Female mice could start breeding from six weeks old, producing up to 10 babies every 19-21 days.

The latest CSIRO mouse forecast recommended farmers monitor mouse activity, consider applying baits at seeding in areas of high activity, and reduce the availability of other food sources.

Mouse activity through Victoria, New South Wales and Queensland remained low, the report said.

Mouse plagues occurred in Australia every four to five years, and they can cause devastating economic, social and environmental damage, one study found.

Historically, significant outbreaks often occurred when several years of lower than average rainfall was followed by rain, Henry said.

“That puts a lot of food in the system and mice seem to breed out of control on the tail of those dry years. That’s certainly what happened in New South Wales in 2021, and here in South Australia.”

The psychological impacts of a mouse plague were “really very profound”, Henry said.

“Mice aren’t like other problems that farmers have. Because, if you’ve got a drought, you can go inside, and close the door and switch on the air conditioner and get a bit of respite from it. But, if you’ve got a mouse plague, you go inside and the mice are in the house and you literally can’t get away from them.”

The agriculture minister, Julie Collins, told ABC radio that farmers were already dealing with the effects of the Iran war on fuel and fertiliser, and that mice would be an additional challenge.