Grain growers in Western Australia are on high alert as mouse numbers reach plague proportions, with similar surges recorded in South Australia. Reports indicate up to 4,000 mouse burrows per hectare in parts of WA, far exceeding the 800-mice-per-hectare threshold considered a plague by the CSIRO.
Steve Henry, a CSIRO researcher specialising in mice and grain industry impacts, confirmed the severity. “In Western Australia we’re now using the P word,” he said. Areas around Geraldton, 400km north of Perth, are worst affected, alongside southern WA wheatbelt regions. On the Adelaide plains, numbers are “extremely high” and “very concerning”.
The current outbreak echoes the 2020-21 plague in eastern Australia, which caused an estimated $1bn in damage, exposed people and pets to pesticides and disease, and contaminated livestock feed and water. The situation could escalate rapidly, with female mice capable of breeding from six weeks old, producing up to 10 offspring every 19-21 days.
The latest CSIRO forecast recommends farmers monitor activity, apply baits at seeding in high-activity areas, and reduce alternative food sources. Mouse activity in Victoria, New South Wales and Queensland remains low. Historically, plagues occur every four to five years, often after dry years followed by rain that provides abundant food.
Henry emphasised the profound psychological toll. “You go inside and the mice are in the house and you literally can’t get away from them,” he said. Agriculture Minister Julie Collins acknowledged the additional challenge amid existing pressures from the Iran war on fuel and fertiliser. Farmers are calling for access to higher-dose zinc phosphide baits, as the current ZP25 strength is deemed inadequate for effective control.
