GRAINGROWERS in areas of SA and Vic where strong winds knocked grain on to the ground prior to harvest are advised to exercise vigilance ahead of their 2020 crop sowing programs to minimise the potential for damage by mice.
Parts SA's Lower Eyre and Yorke Peninsulas, and Vic Wimmera and Mallee, incurred significant head loss in November 2019 when severe winds struck.
Barley crops were hardest hit, but wheat, canola and lentil crops were also affected. In some cases, growers estimate that yields were halved, and losses were up to 2.5 tonnes a hectare.
With such a large amount of grain on the ground, rodent experts supported by the GRDC are warning of the risk of a rapid increase in mouse populations ahead of sowing of this year's winter crops.
CSIRO lead researcher Steve Henry said grain left in paddocks could sustain mouse breeding and trigger higher mouse numbers, which had been at relatively low levels throughout 2019.
"Not only will a large amount of grain on the ground provide mice with a ready food source, it also means there is a reduced likelihood of mice discovering bait," Mr Henry said.
"If strong winds have resulted in 2t/ha of grain on the ground in some areas, that equates to up around 4000 grains per square metre.
"The challenge for growers is to reduce the food load for mice."
Mr Henry said putting sheep on stubbles and strategic cultivation would assist with food reduction, and he encouraged growers to spray out any summer germinations.
"While an ample supply of food does not necessarily lead to an outbreak of mice, if you have high numbers of mice in the autumn, I suggest baiting six weeks out from seeding if mouse numbers are reasonably high, and then following up with another bait application off the back of the seeder if numbers are still high at sowing," he said.
Zinc phosphide bait must be spread according to the label rate of 1kg/ha.
Mr Henry said it was critical for growers to get out of their utes and walk into paddocks to obtain an accurate understanding of current conditions in terms of the amount of grain on the ground and signs of mouse activity.
"I also urge growers to report and map mouse activity - presence and absence - using MouseAlert (mousealert.org.au) so other growers can see what activity is being observed in their neighbourhood and via Twitter using @MouseAlert," he said.
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