UK pest management journalist Frances McKim looks at the changing landscape of rodenticide use across the globe.
In Europe and North America, the way professional pest managers are able to use rodenticides, namely the second-generation anticoagulant rodenticides (SGARs), is changing. UK-based international journalist, Frances McKim, reports on the latest global developments.
Trial ban in Canada
In British Columbia, Canada, a temporary ban to last 18 months on the widespread sale and use of SGARs was introduced on July 21, 2021, following extensive lobbying by Rodenticide Free BC. Rob Hope, general manager of the Orphaned Wildlife Rehabilitation Society, reported that they usually see between 55 and 65 birds at their centre every year that have died from secondary poisoning, a number that has been on an upward trend.
After passing the ban, George Heyman, Minister of Environment and Climate Change Strategy, said, “We share the concerns of many British Columbians that rodenticide use is harming, and too often killing, birds, pets and other wildlife.”
Slow progress in the UK
The problem of anticoagulant residues first came to light in the UK when in 1981, biochemist and keen ornithologist, Colin Shawyer, became aware of the link between the effects of anticoagulant rodenticides on birds of prey. Fast forward to 2016, which saw the founding of the UK Rodenticide Stewardship Regime administered by the Campaign for Responsible Rodenticide Use (CRRU) UK. Tasked with setting and enforcing parameters around the reduction and responsible use of SGARs, its recently published ‘Five Years of Rodenticide Stewardship Report 2016-2020’ found that while progress is being made, there is still a long way to go.
Post-mortem examinations of 500 barn owls revealed that the average level of SGAR residues in barn owl livers had neither increased nor decreased between 2016-2019. Some believe this time period is too short to determine the effectiveness of the stewardship regime, as it took until 2018 for the changes to be fully implemented. Dr Alan Buckle, chairman of CRRU UK, commented that “the high prevalence of low-level residues of SGARs in barn owl livers and the possibility that these residues exert a currently unknown adverse effect” remains an “ongoing and justifiable concern”.
Equally concerning is the high level of resistance amongst rodent populations in the UK. “It is reassuring… that the extension of use outdoors of some more potent anticoagulants has not resulted in a significant increase in the exposure of wildlife [to SGARs] as once feared. Less reassuring is the apparent spread of anticoagulant resistance among target rodent species, including new strains that carry two different resistance mutations,” said Mr Buckle.
One positive finding is that UK professional pest managers appear to be setting a good example in the responsible use of rodenticides, sticking to label recommendations and the mantra ‘the label is the law’.
Australian raptors at risk
Readers may already be aware of the Australian report published in early June 2021 detailing, for the first time, rodenticide residues discovered in wedge-tailed eagles. Undertaken over the last 20 years by the University of Tasmania, residues of brodifacoum and fluocoumafen were identified in 74% of the 50 dead wedge-tailed eagles found in Tasmania. Eagles were exposed to fluocoumafen, a rodenticide only available from professional pest and agricultural suppliers, at what the researchers described as “an exceptionally high rate” of 40% of birds tested.
These results may have contributed towards the APVMA’s rejection of the application for an emergency use permit made by the NSW government to initiate wide-scale outdoor use of bromadiolone to counter the ongoing mouse plague.
In July 2021 the APVMA closed submissions for its public consultation regarding the use of anticoagulant products. A majority of submissions advocated for stricter regulation, including restricting access to certain formulations and product forms (i.e. liquid, gel, wax block, powder, pellet) based on risk; restricting the use of products to secured, single-use bait stations; and updating labelling to include easy to follow usage instructions and clear directions for proper disposal of used baits and carcasses.
With the US having banned the use of SGARs in consumer products in California back in 2014, followed by a ban on the majority of uses of rodenticides containing brodifacoum, bromadiolone, difenacoum and difethialone in 2019, it seems likely that stricter regulation will come into force across the world as more is learned about the ripple effects of SGAR use across the wider ecosystem.