In a rather rare bit of good news for wildlife, the government has announced its intention to ban the use of metaldehyde outdoors. Metaldehyde is the active ingredient in slug pellets, and is commonly used as a pesticide against slugs, snails, and other gastropods.
As well as wiping out slugs and snails, metaldehyde is also toxic to terrestrial mammals and birds, and acute poisoning is common in pets (a 10-pound (4.5 kg) dog may show signs of toxicity after eating as little as 1 ounce (28 g) of a typical 3% metaldehyde bait), birds, domestic, and wild animals including hedgehogs. Hedgehog numbers in the UK have fallen by about 50% since the turn of the century, and while research suggests that the amount of metaldehyde a hedgehog would need to consume to be lethal would be very large, there have been cases of dead hedgehogs with very high levels of metaldehyde in their system (presumably consumed via prey items).
Studies on rats has revealed that slug pellets might affect reproductive ability, but clearly the more direct impact on hegehogs will be the removal of gastropods – a hedgehog’s natural diet consists largely of beetles, earwigs, and other invertebrates (arthropods and earthworms appear not to be affected by metaldehyde), but snails and slugs are taken to varying degrees and with the ongoing loss of habitat that hedgehogs already face, depletion of their food supply can’t possibly help. As the Hedgehog Street website succinctly puts it, “Less hedgehog food = fewer hedgehogs“.
Metaldehyde is known to harm freshwater molluscs as well, and Buglife, the charity dedicated to conservation, education and policy change to protect insects, bugs and invertebrates, said that a ban would “help to create safer spaces for invertebrates“. As an aside, metaldehyde poisoning can also occur in humans, especially in children who accidentally ingest pellets, though it’s usually not serious.
The ban will leave the more expensive ferric phosphate pellets as the only approved active for use on arable crops, although metaldehyde use will still be permitted within glasshouses.
A previous attempt in 2018 to ban metaldehyde in slug pellets was overturned after a judicial review. The High Court in London agreed with a challenge on its legality, which led to Philip Taverner of Chiltern Farm Chemicals, the slug pellet making company which took the legal action to bring the Defra decision before the High Court, to declare “It’s business as usual” – which presumably meant resuming the war on the UK’s wildlife…
Hopefully, the government has got its procedures correct this time and this toxin can be removed from the countryside for good in eighteen months time…
The outdoor use of metaldehyde, a pesticide used to control slugs on farms and in gardens, is set to be banned in Great Britain from the end of March 2022 in order to better protect wildlife and the environment, farming Minister Victoria Prentis announced today.
The decision takes into account advice from the UK Expert Committee on Pesticides (ECP) and the Health and Safety Executive (HSE) about the risks that metaldehyde poses to birds and mammals.
Metaldehyde will be phased out by 31 March 2022 to give growers and gardeners appropriate time to switch to alternative slug control measures. Small quantities of product for gardens should not be disposed of at home and can be disposed of through local authority waste facilities.
While slugs can cause significant damage to farmers’ crops and gardeners’ plants, pesticides containing ferric phosphate can provide effective control without carrying the same risks to wildlife as metaldehyde slug pellets.
Alternative methods of pest control also include cultural techniques like planting slug resistant crop varieties, selectively timing irrigation and harvest and sowing seeds more deeply into the soil.
Farming Minister Victoria Prentis said: “The scientific evidence is clear – the risks metaldehyde poses to the environment and to wildlife are too great.”
Defra, 18 Sept 2020