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 told AAP on Tuesday.

"So they were either pregnant or had recently had babies."

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