An active mouse hole with scats (left); and collected grain (right).
Everyone is aware of the high mouse numbers in our region. Producers will be seeing mouse holes in both crop and pasture paddocks. They may even be starting to see “craters” where foxes and pigs have been digging them up. Mice can cause significant problems to newly sown crops, and if populations stay high, will be a potential problem at sowing. Although it may seem like a good idea to control numbers now, it may be worth waiting.
The reason mouse numbers are high this year is because of the positive season. There is plenty of grass and crop seed on the ground to eat and a lot of grass and stubble that they can use for habitat. While feed is easily available to mice, the results from baiting are often poor. We do not suggest spreading bait while there is still grain on the ground. This feed source can be reduced by rainfall or removal by stock. Farming paddocks could also be worked to remove feed and habitat, but I would think of this as a last resort.
Producers also need to be mindful that although mice will normally only travel 3-5 metres to forage for food, when numbers are high, they will actively travel. So, if you do decide to treat paddocks early, you will need to at least budget on regular perimeter bating to keep them out of your paddocks.
Monitoring is important as environmental factors may naturally decrease the population. Wet weather may cause seeds to shoot, reducing feed as well as flooding holes in low lying areas and cause soil cracks to close, reducing habitat. Dry weather may also decrease feed options.
Our recommendation (adapted from the GRDC and PestSmart resources) is to wait until six weeks before sowing then monitor for mice using baiting cards and by looking for active holes as shown in the image.
If there are high numbers apply a recommended bait product at this time. As you get closer to sowing, you should monitor again. If numbers have increased back to concerning levels, bait should be applied directly after sowing, ideally within 24 hours.
Monitoring should also be done in pasture paddocks, especially those adjacent to this year’s cropping paddocks. When baiting, ensure you read and follow all label directions and observe any withholding periods to achieve optimum results.
For further information:
• The PestSmart website has a lot of use-ful information including a great webinar: www.pestsmart.org.au/toolkit-resource/mouse-control-options/.
• GRDC also has a useful resource: www.grdc.com.au/resources-and-publications/resources/mouse-control.
• For more information on monitoring visit www.grdc.com.au/resources-and-publications/resources/mouse-control or speak to your Local Land Services Biosecurity officer/Ag advisor.