Rodent army rides again

Mouse numbers at alarming levels through parts of Victoria and South Australia


Wade Dabinett, Grain Producers South Australia chairman, says mice numbers in his region are a concern.

Wade Dabinett, Grain Producers South Australia chairman, says mice numbers in his region are a concern.

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Farmers are being proactive in controlling mouse numbers to ensure there is not a repeat of last year's severe crop damage.

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FARMERS are bracing themselves for another year with heavy loads of mice in parts of South Australia and Victoria, while in northern Australia numbers of the rodents are also building up on the Darling Downs.

Some farmers have been scratching their heads as to how mouse numbers have remained so high given a relatively poor year last year and a hot summer, however researchers have said there was still plenty of feed for mice and that summer overall was not hot enough to limit mouse populations.

CSIRO researcher Steve Henry, who is part of a Grains Research and Development Corporation (GRDC) funded project into managing mouse numbers, said hot spots were emerging in areas such as the Mallee and Wimmera in Victoria and the Yorke Peninsula in South Australia.

One reading from data from a recent trapping exercise at Brim, in the southern Mallee in Victoria, indicated there were up to 1000 mice a hectare.

Agriculture Victoria information suggests mice in these numbers could eat 5 per cent of a germinating crop a night.

In South Australia, Mr Henry said members of the Hart Field Days committee had contacted him to get the area monitored for mice numbers due to the concerns they had.

“They felt numbers were very high,” he said.

Mr Henry said results from testing revealed extremely patchy results.

“There is a lot of variation, not just district to district but paddock to paddock, however undoubtedly there will be problem areas and quite bad problem areas at that,” he said.

Wade Dabinett, Grain Producers South Australia (GPSA) chairman and a farmer at Parilla in the South Australian Mallee, said farmers in his area were preparing for high mice numbers once again.

Mice are expected to be a problem this year in South Australia and Victoria in particular.

Mice are expected to be a problem this year in South Australia and Victoria in particular.

“The critical thing will be putting bait out behind the seeder to ensure crops are protected at germination,” he said.

“At a cost of around $3.50 a hectare it is fairly manageable and given the damage last year you would think most people would be doing it.”

He said he would be closely monitoring the situation after the first bait application.

“Given the numbers we have I would not be confident one application of bait will be enough.”

Although baiting is cheap in a single application it is likely to add up to a substantial cost for some growers.

In particular, spring bait applications, requiring a plane so as not to damage the standing crop, can cost up to $12/ha.

Mr Henry said he had heard of one South Australian producer who had spent $100,000 last year on their mouse baiting program and said it was likely there would be similar big spends again this year.

“In the areas with high mouse numbers you are going to be looking at repeat applications and the costs can add up, but the alternative is having your crop severely damaged.”

He said mouse numbers had remained high over the summer.

He said a wet start to the summer had kept mice breeding for longer than usual.

“It only got really hot in January and there was actually a bit of moisture around so although there were some hot spells overall it was relatively mild.”

“There was also a lot of food around for the mice which has kept the population higher.”

With a lot of high profile speculation on whether the mouse numbers could be considered a ‘plague’ or not, Mr Henry urged farmers to consider the likelihood of economic damage or not.

“The numbers required to cause damage are a lot less than what is technically considered a plague, so go out and get tests and see whether the numbers will be enough to cause a problem- the term plague is not relevant.”

Mr Henry said while mouse numbers were as high or worse than last year in many places a pleasing development was how aware of the issue farmers were.

“People are prepared, they have either gone out and done an early autumn baiting or they’re ready to put bait out as soon as the crop is planted, whereas last year the high numbers may have caught people on the hop slightly.”

In the north, Mr Henry said there was an emerging problem on the Darling Downs following the sorghum harvest there but said this was something growers frequently encountered and knew how to manage.

“It is a consistent, predictable problem they tend to encounter every second year in line with breeding cycles.”

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