AUTHORITIES have expressed concern about building mouse numbers in a number of hot spots prior to sowing.
In particular numbers are hitting worrying levels in parts of South Australia and Victoria, with officials also keeping a close eye on matters in southern NSW.
The latest monitoring undertaken by the CSIRO through a Grains Research and Development Corporation (GRDC) investment have led to experts warning of possible crop damage at sowing and in spring.
In Victoria, mouse numbers are moderate to high across the Wimmera and Mallee regions, while in SA, populations are moderate to high on the northern Adelaide Plains, and moderate in the Mallee and on Eyre and Yorke Peninsulas.
Through NSW numbers are not yet at problematic levels but will be closely watched in the lead-up to the bulk of seeding, which will begin to ramp up in the next fortnight.
Mouse numbers are expected to peak over coming weeks while soil temperatures are still relatively warm.
The Wimmera and southern Mallee are expected to have the most significant problems, a victim of their own success with the good yields last year providing ample feed for mice and the thick stubble a good environment for breeding.
Heavy wind at harvest time meant there was even more grain on the ground than would normally be expected.
Birchip Cropping Group (BCG) senior operations manager, Kelly Angel, says Wimmera growers are on high alert.
"Growers need to be aware of the risks. We are in a similar situation to the start of the 2017 season - two years after a poor season, a good crop last year, plus large amounts of grain remaining in paddocks," Ms Angel said.
She told growers they needed to keep a close eye on their paddocks and that despite significant summer rains, visually unshot grain remains in paddocks, especially where it has been suspended off the ground by straw/stubble.
"The assumption that the rains have germinated everything and therefore removed the feed source for mice is probably not entirely correct."
And she warned that just because traditional monitoring techniques, such as chew cards, were not showing significant numbers it did not mean there was no problem.
While mouse chew cards are often an effective method of assessing numbers, Ms Angel says the abundance of food sources could negate their reliability.
"From a visual assessment, we know mice are in paddocks in large numbers, yet that is not being reflected with chew cards soaked in oil.
"Mice seem uninterested in the chew cards as they have plenty of real food at their disposal."
Further out, Steve Henry a mouse researcher from CSIRO, said farmers might not just have to contend with mice in heavy numbers in the autumn.
He said the increase in mouse numbers over autumn in some areas could result in higher than normal survival rates over winter if the crop growing season is a good one.
"This would then mean we enter spring with a larger than normal population of mice as crops advance to grain fill," Mr Henry said.
"That is why it is critical we make every effort to reduce numbers now."
"The challenge for growers is to reduce the food load for mice in stubbles.
"Putting sheep on stubbles and strategic cultivation (burying grain) will assist with food reduction, and growers should spray out any summer germinations."