Farmers in Tamworth and Gunnedah have reported crop damage and have been conducting large-scale baiting, local agronomists have said.

It comes after many retailers have reported a high percentage of mouse trap and bait sales, and CSIRO researcher Steve Henry recently labelled them 'absolute breeding machines'.

Tamworth agronomist Gary Littlejohns said he was seeing "a lot of mice out in the field wherever we go" as a result of the warm weather.

"It's the perfect season for the mice," Mr Littlejohns said.

"In the canola they were pretty active back in October and we did a fair bit of baiting then and there was a lot of dead mice in the field the next day."

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He said to bait the critters, a couple of kilograms of treated grain was dropped out of an aeroplane on farms.

"You're aiming to get about five grains per square metre and if mice can pick up about three of those it's enough to kill them," he said.

"If there's not a lot already in your crop, they're perimeter baiting so that should slow movement. If you've already got them in there you've got to drop across the whole paddock.

"If you're seeing small holes being cleaned out you're pretty likely to have a mouse problem."

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North West Local Land Services cropping specialist, Bill Manning, said Gunnedah farmers were baiting the mice, too.

He said they should be looking out for mice activity, particularly in sorghum crops.

"Just at the moment sorghum is the main issue. There have been mung bean crops go in, and anyone who's got seedling crops, I would keep an eye on those paddocks," Mr Manning said.

"They should probably get some mice cards from the GRDC website and do a bit of a survey of their crops, as well as looking for mouse holes, mouse tracks and signs of mouse activity like damaged heads if crops are out in head."

Mr Littlejohns told the Leader another way to check if mice had taken over was to whip out the canola oil from the pantry.

"If people are worried about mice, stick a bit of paper in canola oil, peg it in the ground, and if you see chewing activity on canola-soaked paper, that's a good way to test if you've got any about or not," Mr Littlejohns said.

"They'll smell canola oil from a long way away."

But both Mr Manning and Mr Littlejohns agree that locals may not be rid of the mice until the cooler weather hits again.

"Unfortunately we could be stuck with them for a while, I suspect," Mr Littlejohns said.

"Typically you'll find it's cold weather that will suppress them."