Farmers in Mingenew and surrounds are reporting crop losses of up to 50 per cent because of persistently high levels of mouse activity, with some reporting it was the worst mouse plague they had experienced.
Mouse activity in WA reached significant outbreak and plague levels across major grain-producing regions, driven by a record 2025 harvest and favourable breeding conditions.
South-eastern Mid West farmers reported the highest impact, including between Mingenew and Morowa, and as far south of Coorow.
The Great Southern region, specifically Esperance and surrounds, also experienced high mouse activity, followed by several other areas across the grain belt.
Mid West grain farmer Andrew Cosgrove plans to start harvest this week.
He said he had to reseed or fallow more than 2000ha of crop because of the mice damage.
“Canola was affected the most by the mice, and we had one paddock of lupins north of Mingenew that got smoked,” he said.
Mr Cosgrove farms 6000ha of canola and lupin in Mingenew, Arrino and Eneabba.
“Our total lupin and canola programs have been baited at least three times, some paddocks four times . . . about 20,000ha of baiting all up,” Mr Cosgrove said.
“That was $200,000 on aeroplanes alone without the bait or counting the cost of crop damage.”
The Cosgroves’ farming properties fell within a marked high zone, according to the Grains and Research Development Corporation for a majority of the growing season, only dropping to a low zone for a month between August and September.
Mr Cosgrove said he anticipated less than a tonne of canola per hectare on affected crops, compared to unaffected crops where he expected 2.5 to 3 tonnes per hectare.
“I can never remember it this bad in my lifetime,” he said.
“We’ve had to clean the wheat out of the hopper every time we filled the truck, it was a nightmare.
“And not only that, but in the houses we were catching up to a dozen mice a night.”
It comes as Rabobank anticipates the winter crop to come down on last year’s bumper harvest at 23.73 million tonnes, 13.3 per cent lower than last season.
Wheat, barley and pulses tonnage was expected to decline, while canola production is forecast to rise to record levels.
Mr Cosgrove said mice numbers could have been mitigated if ZP-50, a double-concentration mouse bait which can only be used under an APVMA emergency permit, had been available at the start of the season and were easier to access.
“The best results on controlling mice were where we baited straight behind the headers before the crop had come up,” he said.
“It’s bare dirt, so the bait was there sitting on top and was easily available for the mice to find it.”
Mr Cosgrove said he hoped the Government and Australian Pesticides and Veterinary Medicines Authority understood the urgency of ZP-50 being available early next year.
“The numbers will still be sitting there over summer, building up again, ready to go,” he said.
“I’ll certainly be preparing for another rough year.
“I won’t be thinking that it is one and done.”
Elders Mingenew agronomist Peter Eliott-Lockhard said there had been significant costs in mouse baiting and crop damage across the region with some farmers reporting losses of up to 50 per cent.
“We have seen a mouse burrow every square metre in some cases,” he said.
Mr Eliott-Lockhard said he anticipated similar mouse activity going into seeding next year.
“ZP-50 will be so important in the early parts of the season,” he said.
“The 25g active does the job in the lab, but it doesn’t do the job in the paddock.”
A Grain Producers Australia spokesperson said mouse activity was consistent in WA over the past few months, South Australia was evolving and the threat in New South Wales and Queensland appeared to have reduced.
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