AUSTRALIAN croppers may soon be looking to confuse, rather than poison rodents to keep them away from their precious crops.
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Traditionally, high mouse numbers have meant one course of action - baiting.
However, University of Sydney research has found promising results by 'camouflaging' wheat seed in a paddock by drenching the surface with wheat germ-based oil.
The theory is the scent of the wheat germ oil will be so powerful mice, which use their sense of smell as the primary method of finding food, will not be able to identify the seed.
The treatments can occur either prior to sowing, meaning the mice no longer associate the smell with food when the crop is planted or after sowing, making the seed difficult to identify.
Researcher on the project Finn Parker, a PhD student at the University of Sydney, said results from a trial in a 27 hectare paddock in southern NSW showed even in heavy mouse infestations the technique was beneficial, with mouse damage to wheat crops reduced by more than 60 per cent even during plague conditions, without killing a single mouse.
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Mr Parker said even a small decrease in mouse damage would have a big impact.
According to University of Sydney data rodents are responsible for an estimated 70 million tonnes of grain lost worldwide each year.
Using this figure it was calculated a 5pc reduction in these losses could feed more than 280 million people, while in NSW alone the 2021 mouse plague was estimated to cost more than $1 billion according to agricultural industry bodies.
He said it was also sound environmentally as it would not have adverse impacts such as secondary poisoning, which, although rare, are technically possible with the zinc phosphide bait registered for use for mouse control in broadacre cropping.
CSIRO mouse management specialist Steve Henry said it was exciting to see another potential method of limiting damage.
"We've been watching this project with interest and it is good to see strong results in the field," he said.
"There is a long way to go of course but this could play a role in helping manage mice, perhaps in conjunction with a baiting program to help keep populations down below those plague proportions."
Mr Parker said mice's keen sense of smell allowed them to identify wheat germ, the nutritious and fatty part of the seed, beneath the ground, and they could dig up seeds with pinpoint accuracy, leading to significant crop losses.
"When a food is too difficult to find, or an odour is not a useful indicator of food they can lose interest quickly and turn to another target food," he said.
"By deploying food odours before food is available, foragers initially attracted to the odour repeatedly receive no reward and learn to ignore it."
He said the work on mice in Australia followed a similar technique to work in New Zealand.
"This technique of camouflaging odours was used in New Zealand to dramatically improve nest survival for threatened shorebirds at risk from by predation by invasive predators like foxes."
"While it worked well in minimising bird predators we weren't sure whether it would work in protecting crops, given how much seed there was in the paddock."
In the NSW trials the plots were sprayed with a fine mist of wheat germ oil, with each application equivalent to the smell of around 50 times the number of seeds in the plot.
Mr Parker said he was confident the method would be able to be scaled up.
"The wheat germ oil is relatively cheap, as it's a by-product, the key now will be identifying what is the sweet spot in terms of the concentration of the oil in the spray."
Mr Henry agreed.
"Once we know what rates are needed we'll be able to figure out whether its economically possible or not, and if it is, from there we'd have to figure out the best way to apply the oil."
Mr Parker said one of the concerns was that rain would wash the scent away, but he said there had been rainfall at application and there had been no great impact on efficacy.
He said there had been two different trials, one with the odour camouflage, beginning immediately after the crop was planted and with the oil reapplied several times until seedlings appeared.
This created a blanket of wheat odour to hide seeds from detection.
The other technique had the oil applied six days before the wheat crop was planted and continued for the week after.
"We predicted that mice attracted to the odour before seeds were planted would begin to ignore wheat odour after repeatedly finding no seeds."
After two weeks, he said the camouflage and pre-exposure treatments had reduced mouse damage by 63pc and 74pc respectively, compared to the control.
"We also estimated that 53pc and 72pc fewer seedlings respectively were lost to mice on these plots.
He said he had applied the spray solution using a handheld garden sprayer.
"The solution will pass through that without a worry so we hope we would be able to do it on a larger scale without difficulty."