Experts concerned the mouse plague is returning worse than before

Experts have major concerns the mouse plague will return even worse than before, with high mouse activity already reported nationally.

Residents had a brief reprieve from the plague over winter, but the rodents appear to have survived in high numbers.

Mice are starting to breed rapidly, particularly in warmer districts in Queensland and Western Australia. Western NSW, which was the worst impacted by the plague, are also seeing signs of the plague's return.

"Unfortunately, we're hearing of higher-than-normal numbers of mice for this time of the year through a large part of the cropping system," said CSIRO's mouse expert Steve Henry.

"That's from Queensland, all the way through New South Wales, Western Victoria and across into Western Australia as well."

The problem is predicted to move from north to south, in line with rising temperatures.

"In those warmer areas, breeding kicks off that little bit earlier," he said.

"We've certainly heard of farmers baiting on the Darling Downs and mice higher than normal mouse numbers in north-west NSW, around Moree and Walgett."

Mice survived winter

Experts had warned if mice survived the colder months by shielding themselves from the elements in burrows, the plague was expected to return in spring.

"Over winter, we've had fairly consistent reporting of mice still being present. That's enough for us to start getting worried," Mr Henry said.

"Unfortunately, we haven't had reports of mice disappearing completely."

"I'm being contacted by farmers who are already seeing those signs of mouse damage," Mr Henry said. 

"Certainly, this year is one where conditions are going to be really favourable for breeding."

"We'd expect breeding to continue into summer, so farmers need to get out into their paddocks and look for signs of damage."

He said farmers should not become complacent, even if they did not see mice yet.

"Be prepared to bait early, hopefully before the populations start to rise too dramatically, and that will help us take the breeding potential out of the population," he said.

Qld farmers 'not mucking around'

High numbers of mice are starting to build up on properties around Mungindi; a town split in half by the Queensland–New South Wales border.

Agronomist Michael Brosnan said, so far, the rodents had largely stuck to the Queensland side.

"A few years ago, we had mice problems, and the same thing virtually happened," he said.

"They stopped at the border – obviously didn't have a border pass."

Cereal crops in the area are starting to show signs of mouse damage. 

"We're very conscious of it, especially as we've finally got a reasonable crop and reasonable prices," Mr Brosnan said.

"You drive around the crops, and you'll see white heads [indicating] the top node of that wheat stalk has been chewed.

"They can do a lot of damage very quickly."

He said several growers were forced to bait crops at the planting stage, which is unusual for the region.

"We haven't had to do that previously," Mr Brosnan said.

"We were expecting high numbers coming into the spring, and that's come through – on the Queensland side anyway.

"We're not mucking around. If we think there is an issue, we're just getting in and baiting."

Earlier this year, rodent bait manufacturers won approval to double the lethality of their products by increasing the concentration of zinc phosphide.

Mr Brosnan said low availability meant local growers had initially struggled to get the double-strength product, but many had started to use it in the past month and were pinning their hopes on it to control future outbreaks.

"Provided they keep that on the label, we will go over wholly and solely to the double strength," he said.

"If we can clean up a bigger percentage [of mice] with the first hit, we're going to be a lot better off."

Floods and frost no match for mice

Goondiwindi agronomist Cameron Derbidge said there were mouse "hotspots" in his area, about 200km north- east of Mungindi.

"I wouldn't say they're getting into crops all over our region, but they're definitely there," Mr Derbidge said.

"Most of the damage is just north of Goondiwindi.

"It's just a matter of time as they breed up and the crops get a bit more mature and push towards closer to harvest where that might do a bit of chewing."

He said the rodents were proving frustratingly resilient to the usual natural killers like floods and frosts.

"I'm just surprised that they got through a flood back in March and April," he said.

"They turned up here last year towards the end of July or early August, and we've been putting out with them since then.

"We've had our usual amount of frost, I would think for winter, and usually, that cleans them up,  but this year it has not.

"I don't know what we do."