With mouse populations at high to moderate levels for this time of the year in some cropping regions of Victoria and South Australia, grain growers are being urged to remain vigilant and take measures during and after harvest to eliminate food sources over summer to reduce the risk of an outbreak in autumn 2018.
Recent strong winds and hail in some parts of the southern cropping region have knocked grain to the ground – combined with any grain spilt at harvest, this will provide a ready food source to maintain mouse populations through summer.
The latest reports from the Grains Research and Development Corporation’s (GRDC) regular mouse monitoring program investment indicate that mouse populations in Victoria’s Wimmera and Mallee regions are high and damage to crops continues, although baiting appears to be effective.
Given current population levels, a moderate likelihood of an outbreak in north-west Victoria next autumn is forecast, but the extent of this outbreak will be dependent on rainfall for the remainder of 2017. Higher than average rainfall over the next two months is likely to promote increased mouse abundance.
Elsewhere in Victorian cropping regions, numbers are moderate but patchy, according to CSIRO researcher Steve Henry, who has completed another round of surveying mouse activity for the GRDC monitoring investment.
In SA, Mr Henry says mouse abundance is moderate on Eyre and Yorke Peninsulas, as well as throughout the Mallee.
“Mouse numbers have declined on the northern Adelaide Plains to low levels, although there has been reports of damage to canola pods and maturing wheat,” Mr Henry says.
Growers are reminded that baiting must not occur within two weeks of harvest, due to the withholding period.
Mice have been a considerable issue for many growers in Victoria and SA in 2017, with 2016’s bumper harvest supporting sizeable base populations over the summer and into 2017, as modelling predicted.
Paddocks supporting heavy stubble loads, particularly barley, were most notably affected by mice as they offered ideal habitat.
Many growers have had to bait multiple times and the success of baiting programs has been variable, probably due to the abundance of alternative food sources.
Mr Henry says breeding started again in early spring in 2017 in cropping regions across both States and he expects numbers will increase through summer and into autumn, when sowing of 2018’s winter crops begins. Reducing the amount of food available to mice through the summer will be critical in containing numbers over the coming months.
Growers are therefore being advised by the GRDC-supported National Mouse Management Working Group to undertake the following activities to reduce food sources and habitat for mice over the coming months:
- Minimise spilled grain in paddocks at harvest as this is key to limiting mouse populations and damage in 2018’s crop. Grain affected by frost and drought is often small in size and not captured at harvest, adding to the potential food source for mice;
- Harvest crops before they are overripe to minimise pod shatter or grain loss;
- Be aware that windrowed crops provide mice with a good source of food and shelter. Try to reduce the number of mice in paddocks prior to windrowing;
- Clean up any concentrated spills of grain around field bins, augers, silo bags and other grain storage;
- Locate bunker storages a considerable distance away from 2017’s crops and ensure storage systems are mouse-proof;
- Consider grazing stubbles to help clean up harvest grain losses (ensure sufficient ground cover is left to minimise erosion potential);
- Remove or reduce cover, including plant material, rubbish and general clutter around buildings, silos and fodder storage as these all provide protection for mice;
- Spray summer weeds and self‐sown cereals to reduce summer and early autumn food sources.
Mr Henry encourages growers and advisers to continue to report and map mouse presence, absence and level of activity using MouseAlert so others can see the scale and extent of localised mouse activity.
MouseAlert also provides access to fact sheets about mouse control and forecasts of the likelihood for future high levels of mouse activity in each grain-growing region.
Meanwhile, the GRDC is proactively investing in research, development and extension so that growers will have new management tools and strategies for mouse management in the future.
Investments include a search for new active ingredients, studies into bait application, research into mouse ecology under no-till farming systems, and ongoing monitoring which is a collaborative project involving CSIRO Agriculture and Food, and the Centre for Invasive Species Solutions.