IF it feels like the mice problem in Western Australia has been worse than usual over the past two seasons, you would be right and with another above average harvest likely on the way, growers need to take extra care to make sure it doesn't carry on for a third year.
Last week, graingrowers across the Wheatbelt gathered to hear the latest advice for managing mouse damage to crops this growing season at a series of in-paddock workshops with Steve Henry, leading mouse expert and research officer from CSIRO.
The field walks visited 11 locations across four days, from Calingiri down to Beaumont, as part of a Grains Research and Development Corporation (GRDC) investment addressing increased mouse activity around WA's grainbelt.
At first glance, damage this season has appeared to be worst in canola crops, however in reality it's the crop getting the most attention because it's worth a lot of money and cereals and legumes have also been affected.
Mr Henry said on the field walks, they had a look at adjoining cereal paddocks and growers were quite surprised to see there was a relatively high amount of activity.
"If farmers are seeing signs of damage in canola crops, in terms of pods on the ground, then they need to be prepared to bait before the mice knock too much other food on the ground," Mr Henry said.
"At this time of year, there's almost no other food around, so if farmers can get bait on the ground now before there is other food about, then they have the best chance of getting a good result from the baiting effort."
The advantage of baiting now is growers take the breeding potential out of the population.
Instead of having 100 female mice per hectare having six to 10 babies every 19 to 21 days, the population is pushed down and instead it's 10 mice per hectare having those babies.
That will potentially buy growers enough time to get the harvest off without contamination.
While it is difficult to quantify the ongoing impact of mouse damage, if growers are looking at protecting a crop which he said was potentially worth $2000 per hectare, then the price of the bait in comparison to the value of the crop was very low.
This is the first year the Bird family, which farms at Yilliminning between Wickepin and Harrismith, has experienced mouse damage to crops.
At a field walk hosted by Facey Group, grower Daniel Bird said after noticing mouse holes in the paddock and mouse damage at crop germination, they have now baited twice, using the recommended 50 grams per kilogram zinc phosphide baits spread at 1kg/ha.
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"We baited 1000 hectares of crop after seeding and then 20 per cent of that area again about six weeks later, as we noted the patches of crop damage were getting bigger," Mr Bird said.
"The canola was planted into wheat stubble, so there would have been a lot of other food around when we baited the first time and that may have led to us having to bait a second time.
"The strip and disc system we use has also left a lot of cover on the ground, which may have contributed to available food for mice."
Mr Bird said access to information from Mr Henry on mouse management strategies was helping to raise the profile of the issue in the Wheatbelt, where mouse damage has not been as common as in the Eastern States.
"This is a new issue for growers in this region, but if mouse damage in crops is going to happen across more seasons, then we need to know how to manage it," he said.
When it comes to limiting mouse numbers heading into next season, Mr Henry said farmers needed to make their stubbles mice unfriendly.
"It's largely about the amount of food which is left behind after the crop is harvested and farmers are starting to focus on getting their headers set up better so they lose less food out the back," he said.
"We get quite frequent reports of a lot of grain being left behind, sometimes up to 300 to 400 kilograms per hectare.
"If the header was set up properly and they were putting that grain in the bin, that's more money for the farmer and less food for the mice during the summer and through to next autumn."
In mixed farming enterprises, livestock can also be used to reduce food in stubbles and what they don't eat is pushed into the soil surface.
With summer rain, those grains germinate and farmers then spray them out to conserve moisture.
Mice only need three grams of food per day.
In some cases farmers are leaving behind 150kg/ha and that equates to 50,000 mouse days of food.
So at 150kg/ha, farmers are supporting 1000 mice for 50 days, on just one hectare.
Ultimately, farmers are getting better at growing crops every year.
"With zero and no-till farming, there is very little disturbance in the paddocks which means there is a lot of shelter for mice due to the retained crop residue," Mr Henry said.
"Because we're better at growing crops and they have been largerly the best two seasons, there is more food in the system more often."
The mouse tours were part of GRDC's $7.5 million national investment into mouse outbreak research, development and extension with CSIRO, focusing on better understanding mice in cropping systems, such as the impact of residual food in stubbles, increasing surveillance and improving strategic management options.
