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Mice movements under the microcope

11 October 2018

$4.1 million grant from the Grains Research and Development Corporation (GRDC) will investigate mouse numbers in zero-till cropping.

A new $4.1 million mouse research and extension initiative, funded by the GRDC, hopes to put an end to re-sowing, yield losses and social effects from mice plagues once and for all – or at the very least reduce it.

According to CSIRO Health and Biosecurity researcher Steve Henry, the social impact of mice in rural communities has been understated with mice invading houses, running across people’s beds and destroying food.

Then there’s the effect on crops. “Anyone who has been through a plague knows the mice follow the seeders which leads to re-sowing and yield loss,” Steve said. “They also climb crop stems to chew nodes and gnaw the flowers in lupin crops.”

Steve said zero or no-till cropping systems in the southern and western zones are contributing to more frequent mouse infestations and these will be a key focus of the GRDC research, announced in March.

“We’ll be determining how zero and no-till cropping systems affect mice and what the key drivers are for mice in those systems,” Steve said.

“We need to quantify the impact of various management tactics (such as strategic tillage, seeding systems, food and habitat reduction) on mouse numbers.

“In conventional tillage systems paddocks were ploughed on a regular basis to control weeds so there was a high level of disturbance and mice lived on the edges of paddocks and only invaded them from the edges when conditions were favourable.

“We now have a system where paddocks almost get zero disturbance – the only time the soil is turned over is when farmers sow the crop.”

Steve said high-yielding crops and heavy stubbles mean mice now have ongoing food and protection.

“Farmers are reporting that they are no longer seeing a plague situation one year, followed by a sudden crash in the population and then a long absence of the pest.

“These days, mice seem to be at problem numbers more often.” He said until now, management strategies were based on research conducted under conventional cropping systems. These included tillage, burning and removal of stubbles, and more livestock than is typical of today’s farming systems.

“Because there’s minimal disturbance these days, mice can dig their burrows out in the paddocks and actually live where the food is,” Steve said.

“We need to do more research to understand what is driving mouse populations and that’s what the money from GRDC is about: determining how mice are existing in a zero and no till cropping system and using this information to develop strategies to reduce the impact that mice have on crop production.

“Technology such as in-burrow cameras and radio-tracking devices will be used to better understand mouse behaviour.”

A key investment of more than $630,000 will expand GRDC’s involvement in national mouse monitoring and surveillance. The aim is to develop a more precise ‘real-time’ broad scale early warning system for potential plagues and equip growers with the ability to proactively manage increases in mouse populations. This will minimise crop losses and reduce economic impacts. A commitment of $275,000 has also been devoted to investigating mouse feeding preferences and bait efficacy.

Broad scale application of zinc phosphide wheat bait (at the prescribed rate of one kilogram per hectare) is currently the only method available for growers to control mice in their paddocks.

“But efficacy of this bait has become an issue,” Steve said.

“Last year sowing was really problematic for farmers. We had some spending up to $100,000 on bait to control mice. Some crops were re-sown up to three times as well. That’s a massive impact.”

The research will explore conditions leading to the apparent reduction in attractiveness of zinc phosphide baits and subsequent lower efficacy – in effect, whether more appealing alternative food sources lead to reduced uptake of wheat-based bait and whether mice stockpile non-baited grain and other food sources in order to survive.

“If so, the research will aim to determine the optimum time to bait to overcome this mouse survival technique.

“Ultimately, the goal is the nationwide reduction of damage caused by mice.”