Northern region grain growers are warned that mice could be a problem in some areas this year, given current seasonal conditions.

Protracted dry periods followed by significant rainfall - as has been experienced by many growers - can be the catalyst for a rapid increase in mouse populations in northern farming systems.

Concerns about a potential problem this year were raised at the latest meeting of the National Mouse Group (NMG), a GRDC investment.

The NMG, which co-ordinates actions to counter mouse plagues, comprises researchers, advisers, growers and other industry stakeholders - including representatives from Queensland and New South Wales.

The meeting was told that flooding during February in some areas, such as the Darling Downs, had flushed mice out of burrows and refuges in paddocks, and that they will be seeking food.

With significant winter crop planting expected following the rains, potential exists for crop damage, especially in germinating chickpea seedlings and mungbeans.

Be alert

GRDC-supported mouse researcher Steve Henry from CSIRO, Australia's national science agency, told the meeting that close monitoring of paddocks for signs of activity should be undertaken.

"Due to drought and, therefore, little fallow spraying, growers may not be aware that mice are present," Mr Henry said.

"Growers need to get out of their utes and walk into paddocks to obtain an accurate understanding of current conditions and signs of mouse activity."

In NSW, mice have been observed in some areas where hay has been delivered from interstate.

It is not clear whether the mice were transported in the hay or if they have emerged from refuges due to the presence of fodder.

To help reduce the food load for mice, growers are encouraged to spray out any summer germinations as soon as possible.

Baiting tips

Mr Henry also emphasised the importance of timing of bait applications for mice.

"It is critical that growers bait six weeks before planting 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," he said.

"A six-week break between applications avoids the risk of bait aversion."

Zinc phosphide bait must be spread according to the label rate of one kilogram per hectare.

Sharing information and understanding

"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," Mr Henry said.

The GRDC's major mouse-related research, development and extension program is continuing to reveal new insights about mice in Australian broadacre cropping systems.

As part of the suite of GRDC investments, CSIRO researchers have been undertaking bait substrate trials to determine if they can enhance the uptake of zinc phosphide bait by testing potential new bait substrates that might be more attractive to mice.

Researchers are testing the willingness of mice to transition from one food to another and then determining whether mice will continue to eat that alternative food source once zinc phosphide bait has been applied.

GRDC research investments have shown that:

• mice prefer cereals over lentils;
• background food significantly affects consumption of bait; and
• strategic use of bait is more effective than frequent use of bait.

The work being undertaken by CSIRO is outlined by Mr Henry in a GRDC podcast and video (see above).

The next phase of the research will examine the role of available alternative food on commercial zinc phosphide bait effectiveness.

Behavioural insights

The GRDC mouse-related investments include a focus on mouse ecology.

This work will involve a series of experiments aimed at understanding how mice function in zero and no-till cropping systems.

Mouse ecology research will address five key topics:

• farming practices;
• managing refuge habitat;
• understanding mouse movements;
• mouse burrows; and
• bait delivery.

Data generated from this work is providing the evidence that, under modern conservation farming systems, mice are remaining in paddocks year-round and establishing large burrow systems.

In previous conventional (tillage) cropping systems, mice would move to fence lines as a source habitat after harvest.

Results from bait substrate experiments, in conjunction with the results of the work in the five key mouse ecology priority areas, will form the basis of a series of recommendations for improved mouse control strategies for Australian grain growers.

A comprehensive GRDC Mouse Control resource hub is available here.

More information: Steve Henry, CSIRO, 0428 633 844.