Dear Readers, it’s been a while since I wrote about slugs, our slimy molluscan ‘friends’, and so with perfect synchronicity I came across two articles with differing points of view this week. The first was in my New Scientist, where American slug expert Rory McDonnell was revealing some very interesting research on how to deter slugs in vegetable gardens and farms. While slugs that are native to a country have largely evolved to become part of the ecosystem and play an important role in breaking down decaying and dead vegetation, other species can become invasive and damaging, and climate change is also affecting the balance of invertebrates worldwide.
McDonnell points out that the number one go-to solution for slug and snail damage across the world is the use of slug pellets, which usually contain metaldehyde. This is poisonous to pets, but also to hedgehogs, song thrushes, frogs and the many other creatures that eat slugs, including some insect predators such as ground beetles. Metaldehyde pellets will be banned in the UK from early this year, though they are still legal in the US. Iron phosphate is approved as an organic solution, but there’s evidence that it could be toxic to earthworms.
Nematodes seem to be a better solution – the species used are native to Europe and seem to target slugs and snails very specifically. McDonnell has found the same nematode species in California and Oregon, but wants to be very sure that the nematodes only kill the pest species of slugs and snails, which has always been my worry about using them here in the UK – only 9 out of the 44 species of slug eat garden plants and some of them, such as the elegant leopard slug, actually eat other slugs. It would be a shame to blast all the molluscs in the garden when only a few are actually eating the lettuces.
However, McDonnell does have a home-grown solution for attracting slugs and snails that he thinks will work world-wide – bread dough. McDonnell found that a mixture of yeast and flour, mixed with water and turned into dough balls, attracts more slugs and snails than anything else that they’ve tried, including slug pellets, beer, decomposing fruit and cat food. Once the hungry molluscs are gathered together, it’s relatively easy to dispose of them, if you are so inclined, or to re-home them if you have a handy bit of wasteland a good way away. Bear in mind that snails, in particular, can find their way home from up to half a mile away, so you might want to pop your molluscan migrants onto the panier of your bicycle and head off into the wilds. Also, as McDonnell notes that they collected 18,000 molluscs over 2 nights, you might need a big panier.
In other news, I note that the Royal Horticultural Society has decided to no longer designate any garden inhabitant as a ‘pest’. Hooray! Although more people complain about slugs and snails than any other animal, the RHS has (belatedly in my view) come to the conclusion that molluscs are an important part of the healthy garden ecosystem, and that, as with aphids and caterpillars, not only are they impossible to eliminate altogether but they attract lots of beneficial visitors such as ladybirds, birds and hedgehogs. The RHS’s advice to those who have slug and snail damage is:
- Grow plants on so that they are older and less tender – slugs do love a delicate seedling. Cloches are also seen as a useful deterrent.
- Slugs are excellent for compost heaps, so they could be collected at night and thrown into the compost. Whether they stay there is anybody’s guess. I suspect this could be combined very well with the bread dough technique.
- ‘Strategic planting’ – put the plants that the slugs love best close to the plants that you’re trying to preserve, in the hope that the slugs will be distracted by their favourite food.
- Dig a pond to encourage the frogs! I have never in my life actually seen one of my many, many frogs eat a slug but they are much more active at night, so maybe they mop them up when I’m in bed. Dig a pond anyway, they are such a source of delight.
- Encourage the birds! Song thrushes do love a snail, but I’m not sure what other snail specialists there are out there. Let me know if any of your garden birds have been spotted with a slug.
- And here’s one I hadn’t thought of – rake over the leaves in the autumn to expose any slug or snail eggs, so that the birds will eat them. In my experience most of the slug and snail eggs are laid on any open or torn bags of compost that I have, so it’s always worth looking at them too.
I know that for many of us trying to keep some kind of balance in the garden, so that it’s welcoming to all kinds of wild creatures without it being overwhelmed by any one kind, is a constant task. Any ecosystem is so finely tuned, and so susceptible to the vagaries of climate and the arrival of new species that it’s easy to just throw up our hands in despair. I do think, though, that given time things rebalance. I am reminded that two years ago my buddleia were so inundated with aphids that the honeydew rained down on the wheelies bins like glue. Last year, there were hundreds of ladybirds and hoverfly larvae – there were still too many aphids but there were less, and they lived for a shorter period of time before being eaten. Who knows what will happen this year? I have avoided the ‘scorched earth’ tactic of blasting everything with chemical sprays because I want that build-up of predators and that rebalancing, but I know that it comes at the expense of things looking as good as they should. But for me, the garden is home to a whole variety of animals, plants and fungi, and I want it to be a welcoming one. As spring gets going, let’s see what happens this year.
You can read the whole Rory McDonnell interview in New Scientist here – you might have to register, but it’s free.
The RHS article is here.
Photo One By Michal Maňas – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=7984616