More and more reports of "patchy numbers" of mice in central-western NSW and across Australia's cropping zone have prompted calls for vigilance to prevent a spring resurgence.
Populations reached plague proportions earlier this year in the Orana region, destroying farm produce, invading stores, sheds and homes in both rural areas and towns, and posing risks to human and animal health.
As spring edged closer this week, CSIRO mouse expert Steve Henry said a return of the rodents was always on the table because there had not been "the monumental crash that often happens at the end of a mouse plague".
While mouse populations had "plateaued" through the winter and in some places "declined", he said there were more and more reports of patchy numbers.
"That's not high numbers, but people are noticing mice around the place and because effectively we're still in the wintertime, that would be cause for concern because it means that we might be getting that higher level of winter survival that we're worried about," he said.
"And that might then lead to mice starting to breed early in the springtime under favourable conditions and numbers going high again."
The new reports of mice were coming from across the cropping zone, including the Eyre and Yorke peninsulas in South Australia, into western Victoria, and the parts of NSW in the thick of the destruction earlier this year.
"As soon as you talk to people, some people are actually seeing them running across the road, through the central west, and to the north of the central west as well," Mr Henry said.
The CSIRO team are telling primary producers to "go for a walk in the paddock, look for the first signs of damage, and as soon as you see that, be prepared to bait".
Mice can munch on cereal crops, canola and legumes.
"So when they [farmers] are starting to see those signs, we're saying be ready to bait at that point, because there's nothing that will make the population go down from here, so the only thing you can do is bait them," Mr Henry said.
"And if you bait them early enough, it gives you a chance of taking the breeding potential out of the population, and bait with the 50g zinc phosphide bait, not the 25g zinc phosphide bait.
"Because we're happy that is a very reliable bait to use, the 50g bait, that's the appropriate strength."
He also says "chew cards" work really well at this time of year because there's not much other food on the ground.
"And that's the other reason we're saying to bait early, is if we can put bait into the system when there's not much other food around, we've got a much better chance of the mice taking that bait," Mr Henry said.
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