YORK producers have joined a growing list of farmers throughout the Wheatbelt who are counting their losses after mice caused substantial crop damage in the last few weeks.
While the majority of experts can't pinpoint just one reason for the large mouse presence or put a monetary figure on how much crop has been lost up to this point, it's widely recognised mice are causing problems from Northampton down to Esperance.
York farmers Charlie Boyle and Peter Monger completed sizeable baiting programs after deciding the detrimental economic outcome of early crop loss was far more significant than the cost of an aerial control solution.
In the last few weeks Mr Monger and his father Rod commissioned a 1000-hectare baiting program which encompassed their whole canola rotation and subsequent paddocks of barley which had been sown back into last season's barley stubbles.
Like most growers in the region, the pair had started to recognise a developing trend.
Landmark agronomist Karrie Stratford, York, also witnessed the same trend over a large number of her clients' farms in the region and said the mice had a tendency to target early sown canola that was now in different stages of early development.
"The mice don't seem to be too interested in cereals at the moment," she said.
"They are also still feeding on last year's grain on the ground.
"Of course that's not to say there has been no cereal damage.
"What damage there has been to cereals is minor compared to the big crop circles they're creating in canola crops all over the place."
Ms Stratford said a large number of her clients had baited for the rodents and some were even considering doing it again.
"The damage really seems to be quite localised to areas where growers harvested Buloke barley last season," she said.
"It's a variety which seems to drop its heads quite easily and there was a lot of grain left on the ground after last year's big harvest.
"Everybody has mice, including the owners of homes, shops and cars in town but where barley was grown last season I've really started to see a developing pattern."
Animal Control Technologies Australia (ACTA) managing director and Invasive Animal Co-operative Research Centre (IACRC) collaborator Linton Staples said he was well aware of the general mouse problem in WA and had fielded a large number of phone calls from throughout the Wheatbelt.
He said about 100,000ha of WA farmland had already been treated, mainly in the Esperance and Geraldton port zones.
"A lot of it is ground spreading because it's the cheapest way to go but as crops start to come out of the ground I imagine aerial treatments will quickly start to become the preferred option," he said.
"It's not a small problem."
Mr Staples said there were three dominant factors which drove, but didn't guarantee, the occurrence of a mouse plague.
"There needs to be a starting population of mice from the previous season to encourage breeding," he said.
"There's also quite often a lot of spilled grain on the ground from a previously good harvest or hail damaged crops which haven't been harvested properly.
"And thirdly, the occurrence of summer rains that prompt early weed seed development.
"In turn, those weed seeds provide a high protein food which triggers early breeding."
Mr Staples couldn't provide an answer as to why certain areas of the Wheatbelt seemed to be troubled by mice more than others.
"It's a guessing game," he said.
But he did say it wasn't the fault of growers or their rotational decisions.
"Swapping to minimum or zero tillage has no effect because communities still suffered mouse plagues when there was a lot of ploughing going on," Mr Staples said.
"It's not due to a failure to burn stubble and it's probably not due to a decline in the sheep population, although all of those things do minimise the food requirement for a mouse."
Though Mr Staples said the term "mouse plague" conjured up thoughts of millions of mice running across roads, scurrying through sheds and causing the complete destruction of newly sown crops, the Wheatbelt's problem was more closely aligned with the term "economic damage."
He said economic damage to crops occurred at a much earlier stage than the catastrophic results of a plague.
Mr Staples encouraged all growers to be vigilant and consider baiting programs.
"If they wait they can lose half of their potential crop," he said.
"For the last 15 years I've seen situations where 30-40pc crop loss has occurred before anything was done about it."
Mr Staples also said there were good stocks of baits for both ground and aerial application available in WA and in the eastern States.