Mouse populations are booming in some of Australia’s key cropping zones, with scientists seeing early warning signs another plague is on the way.
Parts of southern Australia have experienced 20 months of dry weather followed by 200mm of in-crop rainfall, conditions known to trigger a plague, CSIRO research officer Steve Henry said.
There have been increased captures at mice monitoring zones across South Australia’s Adelaide Plains, Yorke Peninsula and Eyre Peninsula, along with Victoria’s Wimmera region.
Trap rates were up to 30 per cent in some of those areas, compared to 10 per cent in an ordinary season, Mr Henry said.
“All of the females we were catching were showing signs of being reproductive,” he said.
“So they were either pregnant or had recently had babies.”
There was less concern about mice numbers in cropping regions in central western NSW and Queensland’s Darling Downs, though monitoring was continuing.
With harvest well under way, mice were unlikely to cause serious damage until next season, Mr Henry said.
Farmers were being urged to harvest as cleanly as possible to limit the rodents’ food supply, then watch out for increased mice numbers in crop stubble.
“By doing that, they’ll have a good understanding of how many mice there are in their stubble and they’ll be prepared to take action by baiting in the lead-up to sowing next year's crop,” Mr Henry said.
After a mouse plague in 2021, which caused an estimated $1 billion of damage across several states, the agriculture industry was better prepared for another disaster, he said.
Subsequent lab tests and field trials helped scientists better understand how the toxin zinc phosphide worked to eradicate mice.
A single rodent needed to eat two or three poison-coated grains to receive a lethal dose.
“What we’ve got to do in the paddocks is create an environment that gives them the best chance of discovering those two or three grains,” Mr Henry said.
“The key driver is reducing the amount of other food that’s around, so mice aren’t distracted by the other food.”
Research after the 2021 disaster calculated the cost of damage to rural NSW alone was $660 million, a figure that informed action to prepare for another plague, Mr Henry said.
“That is a heck of a lot in rural communities and ... a lot of the cost of dealing with mice is borne by the farmers,” Mr Henry said.
“In the rural communities, there’s all of the costs of losing stock in supermarkets, as well as the issues of cleaning up after mice because they just get everywhere.
“It’s much better quantified now that we’ve done that work.”
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