MALLEE farmers in Victoria are anxiously monitoring flowering and budding canola crops for mice damage.
Growers are finding late winter crop damage most severe in canola as opposed to cereal crops, with mice tempted by soft, oil rich canola buds.
Further complicating matters, with canola crops in flower and relatively tall, it is difficult to get conventional, ground-operated bait spreaders into paddocks meaning a contract plane is required to apply bait.
Towanannie, north of Wycheproof, farmer and contractor John White said the mouse problem threatened what otherwise looked like a good season.
“We’ve had good rain, we’ve got canola crops that have got great potential compared to the district average but the mice are a worry.
“There are crops that you could see going 1.5-2 tonnes to the hectare, but others where there are mice issues you can see going only 0.8t/ha or so, there is a big difference.”
Mr White said he had baited twice in the late autumn and had already aerially baited since the mice emerged from their winter period of winter inactivity.
“The total cost of baiting with a plane was around $12 a hectare, which is not too bad considering the crop that is sitting there and hopefully we only have to do it once.”
Claire Browne, research manager with Birchip Cropping Group (BCG) said the organisation had been advised growers were best off baiting sooner rather than later if they felt they high levels of the rodents.
“Bait now while weather is still cool in an effort to keep mouse numbers low at the start of the breeding phase in spring,” she said.
“It is a good way of minimizing numbers of breeding females before numbers start to build up in spring.”
She said farmers may need to bait again as the weather heats up, but added it came down to individual paddocks.
“There is a wide variation in terms of the mouse load, farmers need to make sure they are getting out in the crop and walking around and checking whether they have numbers building up now.”
In terms of identifying potential high mice loads, Ms Browne said chew cards of canola soaked cardboard could be used to get an idea of the presence of mice, while growers also need to be on the look-out for chewed nodes, tillers or buds.
There has been no clear pattern as to where the mice are worst, with various stubble and soil types all having high mouse loads in some circumstances.
Mr White said his worst canola paddock was on a barley stubble.
“It has had issues with mice all the way through.”
Ms Browne said there was no clear pattern as to the worst impacted paddocks.
“There have been a lot of barley stubble paddocks that have been bad, but there have also been issues in pulse stubbles.”
Mr White said he had also had issues with wheat on pea stubble but said canola was the major concern.
“The wheat has patches in it where the mice got in during the autumn and I’d estimate we’d already see 15pc yield damage without any more mice, but canola is the big worry, the mice seem to prefer it.”
He said this year’s mouse plague varied from the last major incident in 2011.
“In 2011 you could see the mice everywhere, all across the road, but the damage wasn’t as bad in the crop.
“This year, we aren’t seeing anywhere near as many mouse just in general but the damage in the crop is quite severe.”
Moving forward, Ms Browne said harvest hygiene would be critical in ensuring there were no problems in 2018.
“Leaving grain on the ground will allow them to build up and be a problem again next year.”
Ms Browne said reports were that crops harvested with stripper fronts, which leave more stubble standing, had been significantly worse for mouse numbers than those harvested with other fronts.
While Victoria and SA are the major hotspots in terms of mouse problems this season there have also been reports in recent weeks of hungry mice causing damage to crops in northern NSW and southern Queensland.