High-tech employed in mouse battle…

A drone can cover more than 180 hectares of cropping with baits in a night.

Producers across the Warwick area are continuing to turn to specialist contractors to battle the region’s current mouse plague, which is causing widespread damage to summer crops.

But the problem isn’t just recent – the mice first arrived towards the end of the winter season in 2020, but recent rainfall spurring on summer cereal crops has provided the mice with a virtual banquet in parts of the cropping country to the north and east of Warwick.

And where’s there’s plenty of feed, they will breed. They’re also becoming more agile – climbing up plant stems to reach higher heads of grain, and digging inches into the soil to devour seeds one-by-one soon after planting of a new crop.

They’ve been described by the experts as “engineers”, and they appear to be highly mobile – producers and eradication specialists are adamant the mice move in ‘waves’ between properties in a particular district depending on what stage someone’s crops are at. A small population will take up initial residence and then feed and breed relentlessly over a short period.

A typical pattern is sheltering during the day in holes dug in a recently-harvested paddock – especially one with new plantings – next to a mature crop which they feast on at night. To put it another way, one paddock serves as the ‘bedroom’ and the other ‘the dining room’.

Despite extensive baiting some producers – including in the Killarney and Emu Vale areas – have lost significant portions of crops such as corn and grain sorghum to mice. In order to protect those crops still in the ground, and newly-planted paddocks, some farmers are calling in aerial bait application, including the use of choppers and fixed-wing aircraft as well as the latest drone technology.

Roger Woods of Cambooya-based firm Drone Commander undertakes a wide range of aerial services for producers across Queensland but for the last several months at least 50 per cent of his and his employees’ time in any given week has been spreading mouse bait on Darling Downs broadacre cropping operations.

Producers purchase the bait – wheat grains coated with zinc phosphide – in bulk quantities and it’s loaded into a ‘hopper’ attached to the drone, which is then programmed to fly over a crop at a top altitude of 30 feet and spread it through a ‘spinner’ at a rate of about a kilo per hectare.

The operations are undertaken at night – when the mice are most active and native birds are roosting – with Roger regularly pulling ‘all-nighters’ to monitor the drones and replenish the bait supply after each flight, some nights covering more than 180 hectares.

Zinc phosphide is an efficient and humane method of mouse eradication – without going into all of the details, it causes a rapid and painless death, including the ‘pups’ in the mouse holes – and results are measured with the use of ‘bait cards’, cardboard pieces laced with an attractant such as canola oil and distributed around the paddock. If the cards are untouched after a night of baiting, it means the operation has been successful.

Mice are also unable to develop a residence to the compound, which is good news if the current problem persists beyond this summer.

Roger Woods says for reasons that are unclear the mice are smaller during the current plague and more agile, and while in the past heavy falls of rain and a cooler snap would kill of a localised infestation they seem impervious to downpours, which at any rate have been patchy of late across the Warwick area.

He also says natural predators – birds for example – seem to be losing their taste for mice which is likely compounding the issue, saying “they’ve eaten so many mice they’re sick of them, it’d be like eating Maccas every single day”.

Roger says the most effective baiting strategy is to carry it out at each stage of crop development – pre- and post-planting, then in-crop, ‘pre-head’ and then at maturity.

Mixed season, apart from the mice…

The mouse issue aside, summer to date has so far seen heavy falls of rain in places over the cropping country east of Warwick, but not everyone has been “under the right clouds”.

Harvesting of grain sorghum planted late in the season will be ongoing and in some cases continuing well after summer, and hay producers have also been busy in recent weeks, keeping an eye on the skies while they’ve had hay cut on the ground.

Later sunflowers are still to be harvested in places – and there’s been serious talk among producers about the need in future summers for the construction of ‘viewing platforms’ for the multitudes of city visitors who make an annual journey to photograph – and be photographed alongside – the Warwick area’s famous sunflower paddocks.

Online forum…

The worsening mouse situation in some of Australia’s key cropping regions will be addressed at a specially convened online forum on Friday 12 February.

With mice ravaging freshly planted summer crops in parts of northern New South Wales and Queensland and in large numbers elsewhere across eastern and southern states, concern is mounting about further impact to summer crops ahead of grain fill and harvest and the potential threat to the 2021 winter grain crop.

The nation’s grain growers and their advisers will be briefed on the situation during a special Grains Research and Development Corporation (GRDC) online Mouse Update on Friday, February 12.

The live streamed Grains Research Update will enable growers to hear directly from GRDC-supported experts from CSIRO, who will provide the latest insights into the extent of the issue and practical mouse management advice for now and in the lead up to summer crop harvest and the sowing of winter crops.

The Mouse Update will begin at 9am AEDT (8am Queensland, 8:30am SA and 6am WA). To register, go to http://bit.ly/2KQRTY1. For further information, contact John Cameron or Erica McKay at ICAN on (02) 9482 4930 or erica@icanrural.com.au.

The Update will be recorded and available for viewing and downloading via the GRDC website.