Clean harvest and farm hygiene vital for mouse control

GRAIN growers across New South Wales are being advised to monitor mouse numbers and minimise grain on the ground during and after harvest to help reduce the risk of outbreaks over the coming months.

Pest experts supported by the Grains Research and Development Corporation are encouraging growers to harvest as cleanly as possible and practice good farm hygiene, especially around grain storage facilities, to reduce the availability of food for mice.

Lead mouse researcher Steve Henry from CSIRO, Australia’s national science agency, said food resources left in paddocks post-harvest could sustain mouse breeding and lead to higher numbers through summer and into autumn winter crop planting.

“There have been good yields across much of northern and central NSW this season and this trend is likely to continue into southern NSW, which increases the chance of grain being left on the ground,” Mr Henry said.

“Getting as much grain as possible into silos will help to reduce the potential for any build-up in mouse populations. Reducing residual food in paddocks will also enhance the effectiveness of mouse baiting activities.”

The latest monitoring undertaken by CSIRO, through a GRDC research investment, indicated mouse numbers were moderate in isolated patches across central western NSW and the Liverpool Plains.

But GRDC Grower Relations Manager – North, Graeme Sandral, said growers in areas of southern NSW were also reporting a build-up of numbers in winter crops, with many concerned about the season ahead.

“A lot of growers still recall the terrible mouse outbreaks in 2010 and 2011 and prior to that in 1993, so they are really keen to avoid a repeat of those high numbers,” he said.

“Even in moderate numbers mice can do serious damage to machinery wiring, so good grain hygiene around silos and sheds combined with baiting in these areas to keep numbers low will provide extra protection.”

Mr Sandral said in a year like this one, in which harvest yields were above average in many regions, it was particularly important to minimise harvester losses to reduce the availability of food for mice.

“The best strategy is to utilise drop trays to accurately measure grain losses and use this feedback to make incremental steps in the harvester set-up. This approach will minimise the food source for mice in paddocks,” he said.

Mr Henry said the improved seasonal conditions were being reflected in increases in mouse numbers at monitoring sites across the State.

“A good season provides ample food and ground cover, in other words ideal conditions for mice. While we do have traps across NSW, there are large areas we can’t monitor so growers need to assess the situation on their individual farms,” he said.

Mr Henry said breeding had started in early spring, and recent and forecast wet conditions, combined with a buoyant harvest, could result in current moderate populations swelling to relatively high densities by autumn 2021, coinciding with sowing of winter crops.

“Growers should remain vigilant and take action if mouse abundance is of concern,” he said.

“Due to the different feed levels between paddocks, growers are advised to monitor across multiple paddocks to gauge mouse numbers to inform management decisions. Mouse chew cards are useful at this time of year.”

Mr Henry warned growers that in-crop baiting was restricted due to 14 day withholding periods before harvest. More details about control options are available via the GRDC Mouse Control website.

But he said where growers had finished harvest, there were actions they could take to help reduce mouse numbers before they started a summer cropping program, or ahead of winter crop planting next autumn.

Five mouse control tips:

• Minimise harvester grain losses. After harvest and prior to sowing – minimise sources of food and shelter: Control weeds and volunteer crops along fence lines, clean up residual grain by grazing or rolling stubbles.
• Apply broad scale zinc phosphide bait: According to the label, at the prescribed rate of one kilogram per hectare.
• Apply bait at seeding or within 24 hours: While seed is still covered by soil, increasing the likelihood of mice taking the bait, prior to finding the seed. Rebait through the season as needed.
• Timing is critical: Delays of 4-5 days in baiting after seeding can give mice time to find crop seed. High populations can cause up to five per cent damage each night.
• Monitor paddocks: Check paddocks regularly and update local data using the MouseAlert website.

Mr Henry urges growers to report and map mouse activity – presence and absence – using MouseAlert (www.mousealert.org.au) and via Twitter using @MouseAlertso other growers can see what activity is being observed in their neighbourhood.

Meanwhile, the GRDC has invested in a major mouse-related research, development and extension program that is continuing to reveal new insights about mice in Australian broadacre cropping systems. The work is investigating mouse biology, ecology and bait efficacy.

Results from current research efforts will form the basis of a series of recommendations for improved mouse control strategies for Australian grain growers.