Australian farmers have been forced to burn their own crops because of swarms of nasty, invasive pests. Following floods and drought, our farmers and regional communities have been battling an entirely different yet equally devastating problem: the mouse plague.

The mouse plague, which started 10 months ago, has seen millions of mice terrorise farmers. They are destroying crops and farming machines. Countless people have woken up to a living nightmare of mice chewing and gnawing at their flesh. Some of these people have been sent to hospital in a critical condition. The severity of the mouse plague has seen this catastrophe gain widespread international attention. But breeding patterns are expected to change and slow down during winter, giving farmers hope that the mouse plague will subside. 

Why do we have a mouse plague?

The infamous mouse plague was brought on by the “perfect storm” of the end of the 2017-2019 drought, and perfect breeding conditions. Farmers first noticed mice during spring of 2020, when they were harvesting a bumper crop. Farms offered the mice plenty of grain to eat, in both the paddocks and in their storage. There were also fewer predators threatening mice, as they had died during the drought. On top of this, regional New South Wales had a mild, moist summer that fostered a breeding environment where mice could breed throughout summer and into autumn. 

Where are the mice located?

Concerningly, there are millions of mice plaguing areas from NSW to southern Queensland, Victoria, parts of South Australia and even Western Australia.

How are farmers battling the mouse plague?

The mice plague has wreaked havoc on farmers’ livelihoods, and their mental health. The damage mice have done to crop yields, machinery and cars has caused losses worth hundreds of thousands of dollars. Regional businesses, especially those in the food industry, such as cafes and grocery stores, have also been impacted.  

On top of the extreme damage mice cause, the cost of bait is only rising alongside demand increases. Aside from cost, many farmers are finding their mice eradication efforts are rendered useless, with the mice being too great a force to combat. Intense debate has taken place as to what bait is most effective to fight the mouse plague. 

Mouse bait options: a growing debate

One of Australia’s most notable grain growers, Grain Producers Australia, has strongly backed the use of double strength zinc phosphide bait, following CSIRO research that found it poses less risk of sub-lethal doses compared to previously registered zinc phosphide bait. The CSIRO research also found the use of double strength zinc phosphide bait was more effective at eradicating mice. 

Despite concerns regarding off-target toxicity, the NSW government has continued with its application for an emergency permit for the use of the rodenticide bromadiolone for broadacre situations. Typically, this bait is used for domestic applications.  

One of the major manufacturers of agricultural mouse bait in Australia has now chipped in on the discussion. Animal Control Technologies Australia (ACTA) managing director Dr Linton Staples claimed that while his company was set to make double strength Mouse Off (a zinc phosphide bait) the standard 25 grams a kilogram zinc phosphide was effective in most situations. 

“With these Mouse Off products, more than 90 per cent of mice are killed within one or two days of application in most rural situations,” claimed Dr Staples

“While some farmers do require second or third applications, as provided on the APVMA approved label, the vast majority of users achieve excellent results after one application with no non-target impact.”

Dr Staples’ views contradict the findings from the CSIRO, which suggested the current products had kill rates as low as 50%. Dr Staples suggested this data was flawed as it was based only on laboratory findings. 

“If this were the case, there would have been many fewer grain harvests over the last 24 years,” Dr Staples said.

Despite the debate, it seems farmers have embraced the stronger formulations of bait, noting their improved efficacy. 

Moving forward: will winter eradicate the mouse plague?

The change in seasons sees a change in breeding behaviours. Mice have stopped breeding with the onset of winter, as to be expedited in the cold months. In fact, they are speculated to have stopped breeding for roughly 6 weeks now, according to CSIRO researcher and notable mouse expert Steve Henry.

While this is promising news, farmers still need to remain cautious, as it is too soon to tell whether the mouse population will take off again in spring when breeding recommences. The return of the mouse plague depends on the number of mice that survive the winter. 

Will the cold bring mice to Sydney?

There has been some speculation that the cold weather could bring mice to Sydney. This is because the city has warmer temperatures and plenty of food sources for the mice. However, these fears contradict the research of CSIRO’s Steve Henry. Despite increased mouse sightings, Steve claims this is nothing out of the ordinary. 

“They only weigh 13 grams and they have tiny little legs. Moving is a really dangerous thing for a mouse to do because it puts itself at risk of predation. They’re only going to move if they run out of food, and they’re only going to have limited movements, until they encounter the next lot of food.”

Notably, Steve cited the notion of the mice moving to Sydney by August is merely rumour – not backed by evidence.  

The mouse plague has been an incredibly unsettling, disturbing and heartbreaking crisis to follow. We’ve been devastated to witness the monumental impact of the crisis on our Australian farmers. Since our inception, we’ve had strong connections with our local farming industry, supplying a range of agricultural equipment and water tanks. We are hopeful that winter will eradicate the mouse plague for our farmers and those affected in regional towns.