Rodenticides could become increasingly difficult to acquire if the current mouse plague continues into the autumn.
A mouse plague that began in Queensland in July 2020 is leaving a trail of destruction that has cost tens of thousands of dollars in lost crops and property damage. Elevated mouse populations have been recorded from Central Queensland down to northern and central west New South Wales, into western Victoria and even into parts of South Australia.
The Centre for Invasive Species Solutions’ online reporting tool FeralScan lists seven major mouse sightings in the past 12 months around Coonamble, north of Dubbo, with mouse populations “widespread and obvious in paddocks”. Queensland farmers have reported seeing mice scurrying among crops in the daylight, with some paddocks completely destroyed. Mice are also getting into people’s homes and machinery sheds in large numbers.
Heavy rainfall at the beginning of 2020 led to a breeding frenzy and a lack of follow-up rain caused a population explosion. It is the worst mouse plague in almost a decade, threatening to undermine post-drought recovery efforts.
CSIRO mouse researcher Steve Henry said that as mice reproduce roughly every three weeks and feast on the stubble of crops, population control is a near-impossible task. The mice have continued to breed through the spring, into the summer and there is concern that they will continue to breed into the autumn, causing trouble for the sowing of winter crops in March and April.
Mr Henry recommended that farmers allow their sheep to graze at crop stubbles to reduce the mice’s food source and to bait at least six weeks before sowing crops. Should that fail, farmers should drop bait straight off the back of their seeders as they sow.
The explosion in rodent populations has also led to a shortage of baits and mouse traps in some parts of QLD and NSW as farmers try to deal with the infestations.
The owner of DJ’s Produce in Charleville, David Jones, said baits and traps had sold out across the region at the end of January. “Every second person that walks through the door is looking for a bait or trap for the mice around town because they’re so bad,” he said. “I’ve had many calls from Roma trying to buy sticky pads and baits because they’ve been unavailable there.”
Jason Green, general manager of Agserv, said that some product suppliers are reporting increased demand for small pack products in plague-affected areas. If demand continues to increase and stock becomes tight in the rural and retail sectors, there is a possibility of widespread rodenticide shortages as pest control product distributors fill the shortfall.
With rodenticides typically manufactured overseas in the US and Europe, and lead times of around eight weeks for delivery to Australia, sudden, large increases in demand can put pressure on supply.
“Our own stock levels are good,” said Mr Green. “In most cases we are holding three or more months’ worth of our popular bait lines. We also carry Australian- manufactured products and at this stage, we have increased holdings of these lines too.
“We’re pretty confident in our own forecasting but can’t guarantee what other distributors may do; if one or two of our competitors runs short, then the additional demand could put pressure on our forecasts.”
Asked whether pest managers might be wise to stock up on rodent baits now, Mr Green says it depends on the situation. “It’s a matter of pest managers looking at their individual portfolios. If they’re servicing large commercial sites or operating in plague-prone areas then it is always going to be beneficial to keep some extra stock.
“If you have particular sites where you could experience unusually high rodent pressure, let your distributor know, as this will help in their forecasting process and ensure that they carry enough stock to meet your needs,” advised Mr Green.
During the last mouse plague in 2011, a rodenticide shortage led the APVMA to approve a number of emergency permits allowing farmers to make their own DIY rodenticides from zinc phosphide.
Such is the nature of mouse plagues, monitoring populations will be critical in predicting what happens over the coming months. With good food levels there is the potential for populations to increase further in some areas but equally, a period of heavy rainfall or a cold snap can cause a rapid crash in populations.
Mouse plague wreaks havoc across two states, destroying crops in Qld, blanketing parts of NSW. Written by M. McCosker and V. Thompson. ABC Rural. January 24, 2021.
Mouse plague hits rural Australia. Otago Daily Times. February 7, 2021.