THE CHAIR of the National Mouse Management Working Group has reaffirmed his support for the use of 50 gram a kilogram zinc phosphide bait where it can be practically applied.
With sowing in full swing in most major cropping regions across the country and recommendations from experts to bait for mice behind the seeder there are significant volumes of bait going out at present.
Ian Hastings, chair of the group and a farmer at Ouyen in Victoria's Mallee, said his simple recommendation was to use 50g/kg bait, which is currently registered for use under an Australian Pesticides and Veterinary Medicines Authority emergency permit in preference to the 25g/kg product with permanent registration.
"All the research work conducted shows that the 50g/kg product is more effective and has less chance of sublethal doses, the message from me would be if you can use it, use it."
Mr Hastings said under the conditions of the emergency permit there were restrictions to the hours where it was permitted to put out the stronger bait, meaning those with 24 hour sowing programs may be forced to also use 25g/kg product.
READ MORE: Monitoring critical in mouse battle
READ MORE: Big harvest creates mouse risk
"We understand there will be cases where people do have to look at the weaker bait but in those cases we'd urge them to look at their potential problem areas and make sure the stronger bait is going out where they think they could have more problems with mice."
He said he did not buy into claims that there had not been enough work conducted on the efficacy of the 50g/kg product.
"There has been a mix between field and laboratory work, it has all found the same thing."
Mr Hastings said cost would not be a major impediment for growers making up their minds which product to buy.
"It is not a matter of double the strength, double the cost, the active ingredient only makes up a small proportion of the overall cost, so you're generally only seeing prices 10-15pc higher for the 50g/kg product, which, when you expect to achieve much greater efficacy that would not be an issue."
In terms of potential off-target species impacts Mr Hastings said there was not zero risk, but said zinc phosphide had been chosen as the best available method of killing rodents because of its low impacts on other species.
"It was the whole reason we did not see bromadiolone registered in the big mouse plague in NSW recently, there was too much risk of off-target death."
The initial work in registering zinc phosphide found very low risk with the product with the active ingredient turning to phosphine gas and degrading rapidly.
In terms of birds taking the bait while it was in the paddock it was found that applying away from native vegetation and having the seed brown so it did not stand out to birds meant there were very few off-target bird deaths as a result of direct poisoning.
Mr Hastings said operationally farmers would get the best results by applying the bait when there was as little feed in the paddock as possible.
"By definition that is at seeding when you've buried any surviving grain from the previous harvest and the planted seed is in the ground, we advise that going in immediately behind the seeder with the 50g/kg product is the best way to minimise the risk of mouse damage at crop emergence."
He said efficacy would vary according to soil type and agronomic practices, such as stubble retention, but said the simple choice was to use 50g/kg bait when possible.
One concern for mouse management group were anecdotal reports that some farmers were sticking with the 25g/kg product because of training requirements necessary to access the emergency permit.
"It is a short, quick course to get your accreditation, it is a bit worrying when people aren't prepared to dedicate a few minutes to help them get on top of what could potentially be a big impact to this year's crops."
He said farmers needed to get an accurate gauge of whether they were likely to have a mouse problem.
"Having an idea of your numbers helps inform your decision of whether to bait at seeding, and its important to get it right as the damage is extreme at this time of year with a young and vulnerable plant."