Recent monitoring and trapping efforts detected high rates of pregnancy in females — adding to concerns about the risk of crop damage at sowing.
Those concerns were raised at the latest meeting of the National Mouse Group, a Grains Research and Development Corporation investment.
The NMG is comprised of researchers, advisers, growers and other industry stakeholders to co-ordinate actions to counter mouse plagues.
CSIRO mouse researcher Steve Henry said the combination of an abundance of grain remaining in paddocks and good rainfall were leading to ideal conditions for mouse breeding, and growers in some areas were already reporting increased activity.
“Parts of the Victorian Wimmera, Mallee, South Australia’s Lower Eyre and Yorke Peninsulas incurred significant head loss in November 2019, when severe winds struck,” Mr Henry said.
“Such a large amount of grain on the ground combined with reasonably heavy rainfall over recent weeks could lead to a rapid increase in mouse populations ahead of sowing.”
Mr Henry said large quantities of grain on the surface of paddocks could reduce the chance of mice finding toxic bait, while providing an ongoing food source.
“If strong winds have resulted in two tonnes/hectare of grain on the ground in some areas, that equates to up around 4000 grains per square metre,” he said.
“The challenge for growers is to reduce the food load for mice in stubbles.
“Putting sheep on stubbles and strategic cultivation (burying grain) will assist with food reduction, and growers should spray out any summer germinations.
“Seeding with knife points assists in burying residual seed — enhancing bait uptake.”
Mr Henry emphasised the importance of the timing of bait applications.
“It is critical that growers bait six weeks out from seeding if mouse numbers are reasonably high, and then follow up with another bait application off the back of the seeder if numbers are still high at sowing.
“A six-week break between applications avoids the risk of bait aversion.
“I also urge growers to report and map mouse activity-presence and absence-using MouseAlert so other growers can see what activity is being observed in their neighbourhood and via Twitter using @MouseAlert.”
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