The focus of our attention this week are the terrestrial gastropod molluscs that frequent our gardens, otherwise known by their collective humble name…Slugs.
The humble slug is the number one pest of the gardener, and routinely tops the Top 10 Pests in the annual Royal Horticultural Society list of most unwanted garden visitors, occupying the top slot 8 out of the past 10 years.
Slugs play an important part in the gardens ecosystem, both breaking down organic matter, such as old leaves but also being a vital food group for many other garden visitors, such as Starlings and Hedgehogs (although the amount of slugs which Hedgehogs eat is widely discussed – thehedgehog.co.uk suggest that slugs and snails only make up around 5% of a Hedgehogs diet). To completely eradicate slugs from the garden would be immensely damaging to the wider ecosystem, instead we try to control their numbers and/or what plants are ‘available’ to be consumed.
The control methods available for gardeners tend to fall into the organic – and non-organic columns, but really the methods are very inter-related and reliance on simply an organic or non-organic slug pellets will not be enough.
This past week I’ve been chatting to Noel Doherty, Head Gardener at the multi-award winning Harrys Restaurant, about how he controls slugs in the restaurants walled garden in Burt and Community Gardener Joanne Butler, who has her own organic garden at home and co-ordinates organic gardening courses in areas including Ards Friary, Gweedore, Letterkenny and Dunfanaghy about how these guys go about slug control and if they’ve any ideas that others could adapt for their gardens.
Here’s a wee run-down of some methods I’ve had success with…and failures…and I always welcome feedback on how others tackle and manage their slug population…
I sometimes cut some leaves from my Comfrey Plants and leave some on the ground overnight, then come out the following morning, lift them up and give whatever slugs are underneath a size 10. This also works with a timber board left in the garden. Simply and effective, but maybe not for the squeamish. Also some plants are repellent, I’ve had some good success using foliage from chives around my cabbages, this works as a repellent to the slugs, try some around your hostas and see how you get on.
According to Noel Doherty, “Vigilance is the key!”. Noel plants successional crops outside after April and is regular inspecting crops for eggs and any early batches to interrupt their breeding patterns, thus giving fewer to deal with later in the season. Joanne Butlers urges a similar approach, “In my own greenhouse I take the vigilante approach , checking under pots and trays in the greenhouse and looking out for eggs (like little clear balls of caviar is the best way I can describe them ) this is a good form of housekeeping as you may find a cluster and eradicate them before any damage is done”
Waste of time. If you’re putting salt onto slugs to dry them (remember from school that slugs are mostly water) yes they’ll dry out, but its immensely time consuming and frankly horrid…and if you put lots of salt around your plants you’ll kill the plants too. Size 10 the slugs instead of watching them sizzle.
Discussed as ‘great stuff’, but it needs to be dry to be effective and most slug damage is done when its wet, so this option seems rather counter-productive in that its not that effective when the slugs are most out! Tried it and its never worked for me.
Now this is good. Water some diluted garlic over your garden plants and this repels slugs – they detest the residual oils that garlic leave behind and will go out of their way to avoid contact with it, and any that have direct contact will die of within hours. The garlic drench will also kill the slug eggs in the soil. You can make your own garlic drench, but the highly concentrated forms available in garden centres are far more effective.
As mentioned before slugs are a stable food source for many garden visitors, Hedgehogs will eat some, starling will eat some, ground beetles and ducks will eat some… but few will only eat them. Slugs produce thick mucus when ‘harassed’ so they’re not exactly caviar. If you have a garden system which encourages a wide range of bird visitors (so try to feed or provide feed stuffs all year – think insects, seeds etc) and a soil which is full of life (remember all that lovely composts, manures, leaf moulds you add ) then this diversity of biology will bring in many grazers of slugs to your garden.
A stable anti-slug tool for years. The slugs are attracted towards the fermented product, and simply drown. Again maybe not one for the squeamish, as of course, you have to empty the cup every so often when it fills up. When you do empty the cup, just tip it out onto the garden, the dead slugs will rot down and feed the soil, or may be gobbled up by something. The choice of beer will determine how effective your beer-trap is however, trials in US found Budweiser to be the most effective, whereas in UK Guinness was found the most effective. Milk also works, and is worth a try if your shy on Guinness. When I’ve used beer traps I’ve placed them 1 to the m2 in ‘hot spot’ areas of the garden and found them to be really good. Noel Doherty from Harrys cultivates many acres of prime vegetables so for him these beer traps he finds are too labour intensive and not worth it in big gardens, “Use organic slug pellets and keep the beer for yourself!” Noel adds.
A hotly discussed topic in the horticultural world and one you may or may not have an interest in. 85% of all gardeners use slug pellets, so it’s more than likely you’ve bought tub this year and chances are you use too much of them. The blue snow effect is something I see a lot in gardens, and something which is highly inefficient. The most commonly used Slug pellet is the non-organic type which contains the active ingredient Metaldehyde – in use since the 1940’s (this is the wee black specs in the blue pellet), chances are the pellet itself (which is the bait) is made from wheat or barley flour. The problem with the blue snow effect is that after 14 days the pellets are of no interest to the slugs as they’ve lost their attractiveness, so you’re better to apply a small amount every 2 weeks, a few pellets spaced 2-3 inches apart is enough. Not handfuls….just a few is enough, correctly applied slug pellets should be almost unseen in the garden. Also within the slug pellet option you have the ability now to use organic slug pellets, these are free from the pesticide Metaldehyde and are instead based on Iron Phosphate (also labelled Ferric Phosphate), this is an ingredient which causes feeding inhibition in the slugs, giving them stomach poisoning. These organic slug pellets are safe for animals, pets etc as long as they are used correctly, if you put more than 4 times the recommended application down you will kill the earthworms in your soil, so stick with the recommended application rate, which will typically be 3 times more than conventional slug pellets. Noel Doherty agrees with me here and adds “A joy of these slug pellets are that the slugs hide away and die, so there’s no mess left behind!”
Sheep Wool (and indeed human hair)
Slugs find sheep wool and human hair very irritable and will avoid it. So if you place a ring of sheep wool or human hair around your slug sensitive plants then this will work as a great deterrent. If you feel the hassle of collecting wool from fences a bit of a hassle you can follow the example of Joanne who uses a pelleted form of sheep wool in the Community Garden at St Conals in Letterkenny, “Slug Be Gone” is the brand Joanne favours and is available in the garden centres.
Old spent coffee granules are another thing that slugs dislike. The caffeine makes slugs to lose their appetite, and are a repellent to slugs. So ask your favourite coffee shop to keep you their coffee grinds and then apply this around your garden plants. This is one which I use in my own garden, and have found it every effective.
These are natural predators you introduce via a watering can to your garden, these microscopic animals then hunt out the slugs, live inside them, lay eggs and kill them from within. And when these eggs hatch they go on to hunt out more slugs, these are super effective (as long as its warm enough – above 12C- and damp enough) a packet of Nemaslug will cost you around 18 euro, will treat 40m2 and will be effective for around 6 weeks (easily purchased on-line)
Slugs are repelled by copper. So on your pots use some copper tape wrapped around the pot (look out for this in the garden centre), also a thick band of copper wire wrapped around your raised beds works wonders. The slugs come in contact with the copper, dislike it and move elsewhere. I’m still using copper wire I got from Geraldine Coyle (Alpha Stainglass windows) some years ago in the raised beds in my own garden. Building on this copper idea, a good copper take, trowel or how used to cultivate between your plants will also leave residual copper behind in the soil, and this will discourage slugs also (GreenHill Farm is your source for these)
Last year in the Dunfanaghy Community Garden Joanne used porridge as a ‘filler’ for the slugs, “this sounded great as the slugs would gorge on the porridge and swell up not being able to eat … But we didn’t take into account the bird problem that we encountered . They were all having a ball on the porridge the following morning and not a slug to be seen.”
Slugs make their own mucus to travel about it, but their journey is made easier by the ground being wet, add in the fact the slugs are largely nocturnal and I always ask myself ‘Why do folks water their gardens at night?’, all you’re doing is laying slug highways! So water in the morning, so excess water can evaporate off before the evening.
I’ll admit to never having done this. I’m not going out in my garden with a torch at night looking for slugs…I’ve got episodes of Modern Family to watch. But folks seem to do this, apparently…do you???
These work on the basis of providing an unattractive surface to the slugs on which to move across. I’ve tried various incarnations of these over the years, my latest was microwaving the egg shells so they go dry enough for me to then break them up and sprinkle around the plants….but I’ve had little success with them, but the crushed egg shells do break up eventually and provide a valuable calcium source for the plants so it’s a bit of a win.
I’ve found that salad leave mixes containing some red leaves to be unfavoured by slugs….
Where do the slugs come from?
You might be thinking this after going through all the above. But a garden typically has around 200 slugs to the m2, with around 95% living below the soil, so what you see are only the remaining 5%! And each slug can produce 90,000 grandchildren the way they breed…emerging every year when the temperature is above 5C and each one of these will have 27,000 ‘teeth’ munching away on your garden plants!!
I don’t believe there’s one ‘holy grail’ for slug control, there’s no one quick fix for a heavy slug problem. But a multi layered approach, over a number of seasons, will dramatically reduce your slug problem into a tolerable level, where they’re ability to cycle nutrients through the consumption of old leaves and other organic matters will work to your benefit.
For more information on community gardens in NW Donegal contact Joanne Butler (+353) 0861789972, OURganicgardens.ie + @OURganicG on Twitter. Noel Doherty, Head Gardener of Harrys Restaurant can be followed on Twitter using the handle @nollaig80. My thanks to the two guys, who despite being unbelievably busy took time out to join me for a chat this week.
Next week….Dare I say…Planning the vegetable garden for Spring…(no I’m not wishing the summer away before you start!!)
Gareth Austin is resident Horticulturist with BBC Radio Foyle, a member of the Chartered Institute of Horticulturists and lectures in Horticulture with National Learning Network. For more see GarethAustin.com or join Gareth on Twitter @GardenerGareth .Tags: