THE threat to southeastern Australia's grain crops from mice appear to have abated, although sporadic damage has been reported by farmers.

Chairman of the National Mouse Management Working Group Simon Humphrys said monitoring by Victoria's Department of Primary Industries had shown all but two of 155 survey sites recorded zero to low mouse activity.

But in NSW and South Australia, farmers were reporting new mouse holes opening up in the past week where no activity had been sighted during previous weeks.

"Farmers are seeing mouse activity but not to the degree where they need to bait,'' Dr Humphrys said.

"They can't bait, anyway, as they are in the two week withholding period for the use of zinc phosphide in grain crops.'' 

Dr Humphrys said the use of mouse baits in southeastern Australia during September and October had "knocked mouse numbers right down''.

He said anecdotally, about 400-450 tonnes of bait had been spread during spring – enough to cover half a million hectares.

He did not believe illegal baits were being used because they would need to be spread by plane and aerial operators were legally liable for prohibited use.

Murtoa district farmer John Gawith said he baited his canola crops by air two weeks ago after finding pods lying on the ground and mice stripping the sides of plant stems.

Mr Gawith said two neighbours had aerially baited cereal crops but he had not found a problem in his wheat crops at Coromby or Lubeck.

Meatian farmer Geoff Nalder said there were mice still active in his area but they were not a problem.

"I came home from a meeting last night,'' Mr Nalder said.

"I hit three rabbits, dodged two sheep, missed a kangaroo but never saw a mouse.''

Mr Nalder said most farmers in the southern and eastern Mallee were not going to bait before harvest.

Victorian Farmers Federation grains group vice-president and Pyramid Hill grower Peter Tuohey said mice numbers were moderate but not causing problems in his region.

"They are certainly around, but not in big numbers,'' Mr Tuohey said.

Dr Humphrys said the threat to next year's autumn crop planting depended on a number of factors, including available food for mice during harvest.

He said modelling in the 1990s showed rain during November was critical to an increase in mouse numbers.

He said the NMMWG would run a "mouse census'' at 12 sites in Victoria, NSW and SA in the next four to six weeks and again at the end of summer or early autumn to feed data into mouse population models.

Mice would be trapped as part of the program.

"This will provide useful data for farmers going into sowing time,'' he said.