Emergency Permit for Double-Strength Mouse Bait Approved
Australia’s chemical regulator has approved an emergency permit for double-strength mouse baits in grain paddocks, responding to severe mouse plagues in Western Australia and South Australia. The Australian Pesticides and Veterinary Medicines Authority (APVMA) has conditionally allowed the manufacture and sale of bait containing 50 grams per kilogram of zinc phosphide (ZP50). This decision comes after months of pressure from farmers and rural community leaders who have been struggling with the impact of the mouse infestations.
Mice have invaded homes, sheds, and farms, causing health concerns and significant damage to emerging winter grain crops. Farmers are now hoping that access to stronger bait will help them manage the crisis more effectively.
Impact on Farming Communities
In Northampton, WA’s Midwest, grain farmer Scott Bridgeman expressed relief at the new permit. He said having access to the stronger bait would give him “more confidence” in managing the mouse problem. “One seed is one death,” he said, highlighting the effectiveness of the higher concentration bait.
Bridgeman described the destruction caused by mice in his paddocks, noting the extensive network of holes and the amount of dirt they have moved. “It’s amazing how much dirt a little animal can move,” he added.
Across WA, growers have reported mice eating planted seeds before they could germinate, leading to crop damage. Retail manager Ben Lang, from Northampton, said the store was struggling to meet the demand for bait and traps. “If I’m not ordering 100 mouse traps then there’s something wrong,” he said, adding that people in town had thrown out hundreds of dollars’ worth of food.
A Problem That Began Months Ago
The mouse plague has been ongoing for months, with a study earlier this year by the CSIRO estimating up to 8,000 mice per hectare in parts of WA’s northern grain belt. Farmers had raised concerns about the issue, but the rodent population continued to grow, spreading into towns near grain paddocks.
Community leaders, including Morawa shire president Karen Chappel, have criticized the APVMA for its slow response. She called the delay “tardy and irresponsible,” arguing that the agency prioritizes wildlife over human life. “Until the mice issue in the paddocks is dealt with, we are not going to be able to reduce the number of mice in town sites and homes,” she said.
Relief for Farmers
Grain Producers Australia (GPA) had been lobbying the APVMA for an emergency permit to provide farmers with access to ZP50. Andrew Weidemann, from GPA, said the approval would be welcomed by farmers. “While grain growers have had ongoing access to 25g/kg zinc phosphide (ZP25), it’s not strong enough to tackle the level of mice issues that we’re seeing at the moment,” he said.
Weidemann emphasized that the national emergency permit is designed to be flexible, helping farmers with moderate or high levels of mouse activity. Farmers will need to be trained and accredited before using the bait, and information on training can be found on the GPA website.
Worst Plague on Record
Residents in regional WA have been dealing with what many describe as the worst mouse plague on record. Northampton resident Erika Brown described the situation as “disgusting, it stinks, it’s filthy and horrific.” She has been relying on bucket and cage traps instead of poisons, but even her chickens struggle to keep up with the mice.
The APVMA stated that the permit includes specific use instructions and controls to support effective mice management while minimizing risks to people, wildlife, and the environment. These include clear directions on application to reduce exposure to non-target animals.
Long Road to Approval
The APVMA had previously rejected an application for the higher-potency baits, citing insufficient regulatory quality in the research provided. However, data from the CSIRO, which published four papers examining zinc phosphide efficacy, showed that the 50g/kg rate was more effective than 25g/kg in controlling mice.
CSIRO research officer Steve Henry, who co-authored the studies, stood by the findings. “Effectively, all four studies have shown exactly what farmers were telling us, that the 25g/kg bait doesn’t work consistently,” he said. While no indication of increased risk of secondary poisoning to birds has been found, scientists continue to study this area.
