Damage caused to wheat crops by hungry mice can be drastically reduced by using wheat germ oil to disguise the smell of their favourite wheat seed snack.
Scientists at the University of Sydney, Australia, discovered that camouflaging the smell of wheat seeds can prevent mice from being able to locate them, reducing seed losses by almost two-thirds (63%).
Damage to wheat crops by mice is a major problem in Australia, with mouse-caused crop losses totalling $1bn AUD (£542.8m) in New South Wales 2021. Around the world, rodents are responsible for an estimated loss of 70m tonnes of cereals each year.
Relatively few effective controls are available for tackling rodents — especially when it comes to biocontrols. Until now, producers mostly use zinc phosphide at sowing, but stronger doses are increasingly needed to manage mouse populations.
In research published in the journal Nature Sustainability however, scientists said disrupting the ability of mice to forage and sniff-out food is a safe and sustainable solution that could be a game-changer for growers.
In trials carried out on a farm in New South Wales, the researchers treated 60 plots with either a solution of water and wheat germ oil — a low-cost by-product of the milling process — or canola oil. The remaining plots were trampled and left untreated.
All of the untreated control plots saw the most mouse-inflicted crop damage, but seed thefts were cut by 63% when plots were sprayed with diluted wheat germ oil after sowing.
If the plot was sprayed with the same solution before sowing, losses were cut even further to 74%.
“Olfactory misinformation tactics”
The researchers said mice rely heavily on their sense of smell to find and dig-up newly-sown seed, “precisely targeting” a seeds location by the smell from the wheat germ.
By spraying the ground before and at the time of sowing, the smell of the seeds was camouflaged and mice were less inclined to dig the soil to search for them.
The camouflage treatment lasted until after germination, they added — the period when wheat plants are most at risk and need to be protected.
“When the smell of the seed is everywhere, they’ll just go and look for something else instead of being encouraged to dig,” said the University of Sydney’s Professor Peter Banks, one of the co-authors of the study.
“That’s because mice are precise foragers that can smell seeds in the ground and dig exactly where a seed is, but they can’t do that in this situation because everything smells like the seeds.”
The researchers said the “olfactory misinformation tactic” could work well in any crop systems with pests that find food by smells.
Because mice can’t evolve resistance to the method, because it uses the same odour they rely on to find wheat seeds, it offers a sustainable, and non-lethal, alternative to poisons and baits, they added — even in plague conditions.
The teams’ discovery could help wheat farmers at a vital time in Australia: In 2021 mouse plagues caused millions of dollars of damage in New South Wales, and GRDC figures suggest numbers are on the rise again.
The scientists plan to do further research to understand the concentration of oil needed to repel mice, as well as how often the solution needs to be applied to prevent mice from digging up seeds.
