Mice on radar after favourable season

Biosecurity SA research officer Greg Mutze said this season had several indicators that mice numbers could rise to problem levels in the coming months.

“The first thing that determines numbers is the total amount of grain produced in the previous year,” he said.

“They feed on grain spilled at harvest and with more grain produced, if harvest efficiencies don’t change, then more grain will be on the ground. It is likely that with more food, the population could build up in summer and autumn.”

Mr Mutze said SA also had experienced another major indicator – unseasonal rain – which would extend the food supply in damaged crops or germinating weeds.

“We’ve had a year of really heavy crops and unseasonal rain and the last time we had a similar set of circumstances was in 1992-93,” he said.

“There was a widespread mouse plague through SA in 1993.”

CSIRO researcher Steve Henry, who has been surveying mouse activity for a GRDC-funded project, also warned the conditions favoured population build-up.

Mr Henry said SA monitoring stations showed relatively low numbers so far, but mice had started breeding earlier than usual on the Adelaide Plains.

“Growers should remain vigilant,” he said.

Mr Henry encouraged farmers and advisers to report and map mouse presence, absence and level of activity on the MouseAlert website.

“We need more producers using MouseAlert so that the project can deliver more accurate forecasts of regional changes in mouse numbers,” he said.

Mr Mutze said there were steps farmers could take to reduce the risk.

“For those on mixed farms, they could put sheep through stubble to clean up as much of the spilled grain as possible,” he said. 

“The second main thing is summer weed control so when the spilled grain food resource runs out, they run out too.”

Mr Mutze said it could be difficult to use other methods of controlling mice numbers at this stage, with regular rain events making spraying costly.

“The evidence we’ve got shows baiting right at the time of sowing seems to be the most effective way to limit damage,” he said.

Graingrowers are also cautioned, if using bunkers to store grain, to locate the bunkers away from crops.

Grain storage specialist Peter Botta said moving bunkers away from crop areas would limit the likelihood of mice travelling from crop stubbles to bunkers.