With the effects of last year's mouse plague still fresh, farmers and rural communities are being warned to act now to avoid a spring rodent breeding boom.
Reports of high mouse numbers are increasing across the eastern states as well as a "significant outbreak" in Western Australia.
CSIRO researcher Steve Henry said while it would be "unusual" to see mouse numbers at plague levels again this year, it could be possible if control action was not taken.
He said taking proactive measures now would reduce the spring breeding population base and help protect valuable crops.
"Obviously there are some really high value crops, particularly canola crops, that are being sown at the moment, and it's really important to protect those crops," Mr Henry said.
"But the added benefit of protecting those crops is that we'll be pushing [mouse] numbers low as we go into winter.
"That potentially reduces the over-winter survival of populations which means next spring when they start to breed again, they start to breed from a lower population base and the rate of increase is slower."
Monitor and act now
Mr Henry said one active burrow in 100 square metres could equate to about 200 mice per hectare.
"If you make an assumption that there's two mice per active burrow … and then we know mice have six to 10 babies every 18 to 21 days, if you've got 200 mice per hectare, you're not very far away from a big problem."
Mr Henry urged farmers to bait as soon as possible after sowing.
"Bait, continue to monitor, look for signs of damage, monitor to make sure that you have got a good result with your baiting effort and if possible, bait with the 50 gram zinc phosphide."
Mr Henry said fortunately, there were few reports of mice activity in Central West NSW which was hard hit by last year's plague.
"It was been incredibly wet through that area and I know farmers are just sitting waiting for the country to dry out enough to sow it, so we might start to get more reports once the crop starts to go in," Mr Henry said.
Chew cards to monitor mouse activity are available from the Grains Research & Development Corporation website and sightings can be reported to the MouseAlert website.
Cost still taking a toll
The 2020-2021 mouse plague devastated farmers after the drought and not even floods could end the rodents' rampage.
"I suspect farmers this year are significantly more vigilant than they have been in the past, simply because they were so terribly affected last year," Mr Henry said.
North-west NSW grain grower and NSW Farmers vice president Xavier Martin said no one wanted a repeat of last year.
"There were hundreds of thousands of [dollars of] damage on some farms," Mr Martin said.
Mr Martin said there was "just enough activity to keep farmers alert".
"We're fortunate, at the moment, that we don't have any out-of-control spots that we're aware of, but the only way that we'll maintain that is by being vigilant and responding.
"Being vigilant and monitoring is absolutely critical to avoid that plague taking off.
"And we don't want that to happen again."
