Key points

• Previous experience of the damage caused by mouse plagues helped inform Bruce Watson’s decisions to reduce plantings
• However, mouse control still cost him $100,000
• Management included baiting, ploughing and changing the planting program

Just over a decade ago, New South Wales grain grower Bruce Watson lost 400 hectares of newly planted hybrid canola to mice.

Bruce, a GRDC Northern Regional Panel member who farms 3500ha with his family at Parkes, recalls the 2010-11 plague was costly. It led him to approach the most recent plague a little differently, protecting sensitive crops, tilling some areas and holding back on planting some crops.

“The decisions we made followed on from our experience in 2010-11 when, after a big, wet harvest, we had a lot of mice,” Bruce says.

“This time, we didn’t want to throw money at the problem. We decided not to chase certain crops in high-risk scenarios, and decided to wait for the mice to crash, which they will inevitably do. And then, if there was enough rain, plant chickpeas – which we did do – and our significant sorghum program.”

That said, mouse control still cost Bruce upwards of $100,000. That included initial baiting, baiting behind the planter and re-baiting certain areas of the farm. “Sorghum planted in November 2020 was baited three times during the season, double-crop mungbeans were baited four times. It adds up.”

Losses were reduced, but mice still reduced yields in sorghum by five per cent and in mungbeans by 20 to 30 per cent.

Looking back, Bruce is happy with the decisions made. “We would not have done anything differently.

“For us it was a matter of targeting our low-risk country for planting first, such as our canola stubbles into cereals, and then assessing the situation.”

For those committed to a winter cropping plant, Bruce says, his strategy of ploughing and baiting, and then baiting behind the planter, worked well.

“It is hard to do as an industry given our focus on zero till and controlled-traffic farming, but it is the lesser of two evils given the need to generate income and also control mice.

“Yes, you may lose topsoil and some moisture, but I think it works as a mouse management strategy. Don’t fight nature. With the help of baits, they will eventually die off.”

Quirindi agronomist and fellow Northern Panel member Peter McKenzie echoes Bruce’s thoughts.

Peter says growers might have more confidence in different management strategies in the future, including getting on to the problem early with baiting.

“Baiting is expensive, but so is extensive crop loss. I think we will see more confidence in the economics of baiting going forward, especially going hard and early.”

He says many growers came up with their own thresholds of what was acceptable when using chew cards. “One thing that was really apparent was that paddocks that had deviations, or pastures or waterways around them, became heavily infested and were really hammered.

“We’ve learnt to be more intense with baiting in these zones. And it showed. In some areas, where people hesitated, the yield losses were significant at three to four tonnes a hectare.”

Although mouse numbers have dropped off, the CSIRO rodent management team is still busy. Team leader Dr Peter Brown says their mouse research program is looking at improved predictive modelling, understanding the diseases present in mouse populations and informing better management decisions.

“The emotional and financial toll to farming and rural communities will also be explored. During these bumpy years we do not see the financial costs reflected in our GDP (gross domestic product), which means growers and rural communities bear the cost and it is distressing,” Dr Brown says.

Dr Brown started working on mouse plagues in 1993, when the team consisted of himself and Steve Henry. The team has since expanded to include 10 researchers.

Many growers are familiar with Mr Henry, a well-recognised and trusted researcher. CSIRO estimates suggest that via hundreds of interviews, many with Mr Henry, its messages reached the equivalent of 85 million people in 2021.

Both Northern Panel members are very appreciative of the CSIRO team. Peter McKenzie says Mr Henry helped everyone through a tough time last year. “He must have been getting hundreds of calls a day and he did a fantastic job taking the time to talk to all of us. I can’t speak highly enough of Steve.”

More information: Bruce Watson, 0408 464 776; watson.woodbine@gmail.com; Peter McKenzie, 0428 474 860, pete@agcon.net.au