He said reports were coming in from across the State of widespread activity.

"Most of the farmers I've been speaking to in the past month have noticed more activity in their paddocks than in previous years," he said.

"It is probably at least the level we saw before autumn last year.

"The wet weather we've had is going to be germinating weed seeds, which will then become a food source and cover for mice living in paddocks.

"So the risk of farmers having to deal with mice this autumn is increasing."

But Mr Humphrys said farmers should not be stocking up on bait just yet.

If feed sources run out before seeding, mice numbers could crash in as little as a week.

"The main thing the working group is doing at the moment is organising mice monitoring in New South Wales, Victoria and South Australia," Mr Humphrys said.

"Before the end of this month, we'll be out at five to six sites in each of the states, trapping mice and looking at whether they are still breeding.

"We'll be using this information in some modelling software developed by the CSIRO and coming up with a series of scenarios based on average rainfall to now and seeding time, above average rainfall and below average rainfall."

Mr Humphrys said this modelling should give farmers a month of fair warning whether mice numbers would be high or low at seeding.

"What farmers should be doing now, if they're able to, is heavily grazing any summer weeds," he said.

"Where heavy grazing is not an option, summer weeds should be spray-topped."

Mr Humphrys recommended particular attention to controlling summer weeds on road verges and along fencelines.

It was also important to make sure screenings in paddocks or around field bins were cleaned up.

The working group had conducted a survey of farmers aimed at trying to determine whether certain practices undertaken in 2010 influenced the severity of mouse problems in 2011.

"From the survey data, there wasn't any real clear-cut activity that stood out," Mr Humphrys said.

"We're now having to drill down on whether there are any specific practices farmers had undertaken that on a neighbour-by-neighbour basis gave one person an advantage over another."

Mr Humphrys said it was unlikely the Australian Pesticides and Veterinary Medicines Authority would issue emergency use permits this season.

* Full report in Stock Journal, January 12 issue.