Big harvest creates mice risk

Severe winds in late October and early November created heavy damage and left grain on the ground, while the size of the harvest itself has resulted in grain spills.

"It's not a total blanket area, but it extends from Ceduna right through to Loxton and covers large areas between the main cropping zones," Ian said.

"And the reason that we're concerned with that particular area is because of the wind damage that occurred and the amount of grain that is now on the ground.

"We believe it has the potential to create a major problem with mice as we go into autumn."

Biosecurity SA research officer Greg Mutze says spilled grain in paddocks is the reason why mouse numbers build up so rapidly, and damage next season's crops.

Mouse populations usually spiked in the year after a 'bumper harvest' because a small percentage of a large harvest could equate to a significant amount of feed.

"Some areas also had bad wind damage last year that dropped a lot of grain before harvest," Greg said.

"That is the worst possible scenario if combined with summer rains that promote weeds and mouse habitat."

But Greg said the problem was compounded by many farmers growing Clearfield Scope Barley for a second consecutive year in 2013 because a lack of rain in the 2012-13 summer meant chemicals that were specific to growing Clearfield varieties had not been washed away.

"One of the few bad traits about Scope Barley is that it drops its grain and is susceptible to lodging, and therefore wind damage," he said.

"It's one of the things that's contributed to the amount of grain on the ground."

Ian said farmers would be encouraged to bait for mice, with the most effective time to bait within the first 24 hours of seeding.

"The NMMWG is trying to ensure that we've got enough bait available and at the moment that is still a problem for us," he said.

"Farmers don't as yet have the ability to be able to mix bait on farm.

"We've been trying very hard to get to that point, but we're not going to be there in time for this year."

A serious mouse plague caused major problems across Australia in 2011, negatively affecting 3mha by autumn and costing growers about $200m in losses.

It prompted calls to allow farmers to mix their own bait on farm with zinc phosphide, which would have dramatically reduced the comparative costs of buying pre-mixed bait.

The request was denied, and instead the Australian Pesticides and Veterinary Medicines Authority issued a number of emergency use permits that allowed zinc phosphide bait products to be formulated with unsterilised grain at existing and regional formulation sites.

It allowed Western Australian distributors 4Farmers to set up seven SA mice baiting stations, at Crystal Brook, Kadina, Lock, Wudinna, Wirrulla, Cowell on the Eyre Peninsula and at Balaklava, to boost ailing supplies.

Greg said there seemed to be plague situations in areas that were more prone to damage, and mice populations rose rapidly if food sources were plentiful.

* Full report in Stock Journal, January 16, 2014 issue.