Steve Henry, a CSIRO researcher looking into mouse numbers with funding from the Grains Research and Development Corporation (GRDC), said while mice generally did not breed over winter, several reports had come in of abnormally high mouse loads for this time of year.

“We’ve got reports of farmers actively spreading bait already, which is very early. They had been noticing tiller damage.”

He said the problems were worst in the areas that had high mouse numbers in autumn, such as South Australia’s lower Mid North and Yorke Peninsula and the Wimmera in Victoria.

“There’s no doubt people are concerned. Agriculture Victoria held an event regarding managing mouse numbers, expecting 30-40 farmers across three days, instead there were 200,” Mr Henry said.

He said the key piece of advice for growers was to get out and closely investigate paddocks.

“With the crops growing, it is not really possible to pick everything up from the ute cabin. You need to get out and have a walk between the rows to really get a feel for what is happening.”

Mr Henry said he felt baiting would be necessary for many growers again.

“It is quite concerning the early reports that appear to show a reasonable population of mice has survived, and with a good season for crops it is very likely they will begin to breed up again.”

He said each female mouse was capable of producing up to 500 offspring a season, meaning numbers multiplied to problem proportions very quickly.

Steve Schultz, a Kalkee farmer, north of Horsham, said mouse numbers were noticeable but not yet at problem levels on his Wimmera Plains property.

“You can find them if you look hard enough for them, but in general they are not yet as big a problem as they were in the autumn.”

The 2017 mouse plague has been most significant in SA and Victoria.