Thursday, 28 February 2013

Our slimy friends



Slugs and snails
When visiting parties used to come to Bolton Percy cemetery I was often asked why my hostas were not damaged by slugs! Funny, when gardeners get together they always talk about slugs. It must be a measure of slugs’ success in eating our plants!  The observation about my plants was scarcely true, but did reflect that my hostas were healthier than  those in normal gardens. According to gardening lore, garden hygiene such as avoiding plant debris reduces slugs. With my methods of directly recycling fresh organic matter what’s going on? I have argued for years, perhaps tongue in cheek, that it did not matter a damn if I encouraged more slugs, as long as they were doing what nature intended, eating decaying organic matter which they prefer. Indeed it’s part of the natural cycle of decay. Slugs have an image problem.They need to employ Bartle, Bogle and Hegarty, we would soon be singing their praises. “Put it this way”, I say in my lectures, “no wonder the slugs eat your hostas, if you clear away all garden debris there is nothing else for them to eat!”
There is  some scientific support for this idea. First I must explain, that there are hundreds of different slugs and snails. What is true of one may not apply to another. In this post for convenience I write ‘slugs’ when I mean both slugs and snails. Years ago, I read an interesting article in the ‘New Scientist’ about slug slime trails. These are super-highways for slugs which they continually re-use as they zoom around our gardens. I found it very interesting to read that the more slime trails they crossed, the less fecund they become. It’s a natural way of controlling their own population. If true, it’s rather ironic, that all those gardeners -  often eccentric academics - who go out at night with a torch, ‘picking slugs’ merely succeed in making them breed faster!  


A lady recently did an interesting piece of valid research that if you pick up a snail and fling  it away, unerringly it will find it’s way home!
Fancy a drink at the Slug and Pebble?



Slug biology
They are the only land living mollusc. I love the word gastropod, the name of the group to which they belong!  An interesting feature is their rasping tongue called a radula. It’s a kind of ribbon with thousands of replaceable backward pointing teeth (I don’t mean dentures!) Like sandpaper it scours the plant leaf to produce the damage illustrated above. Slugs are hermaphrodite and have a very interesting sex life, but I will not go there! 



Water snails

Using  slug pellets
I despair when I see blue mulches of slug pellets. I break out laughing when I see  ‘protective circles’ of pellets around plants. Don’t the blue mulch brigade realise that pellets are a poisoned bran bait and that such large quantities are a danger to domestic pets and wildlife! Pellets only need to be used in miserly amounts, half a dozen pellets a square meter will usually do the job. For my acre garden, a standard tube of pellets lasts me about three years - and most of these are used in my greenhouse!  As to the protective barrier idea, the bait brings the slugs right up to your plants where they may very well decide that your plant is rather tasty! Pellets should be scattered a short distance away from your vulnerable newly planted brassicas.
There is an important issue as to whether slug pellets are safe to wildlife. If used sparingly in the domestic garden, I believe that they are safe, although I cannot vouch for their widespread use in agriculture. Best to apply the pellets under a canopy of plants. It is suggested dead slugs might be eaten by birds but this is disputed. Pellets really are dangerous in packets accessible to cats and dogs. There have been tragedies where pets have eaten poisoned bran direct from the pack. I am told that these days, bran is treated with animal deterrent. 

The most vulnerable plants to slugs are those that are newly planted. Perhaps that’s because they are soft from a previous propagation environment or as many gardeners believe, slugs ‘smell the stress in a wilted plant’. After all, as stated previously, their preferred food is dead plant tissue. On the rare occasions I use pellets outside, I apply in the evening before I am due to plant. Try and use pellets where and when they will remain dry. Wet soggy pellets are of little interest to slugs and the metaldehyde poison becomes completely ineffective.

There are  a legion of methods of slug control. Most are fiddly or ineffective and may not be wildlife friendly. For example ‘slug pubs’ are likely to kill desirable ground beetles. I would be very interested to hear of your own successful methods. I understand that wildlife friendly slug pellets are now being marketed. But read these doubts. In 95% of my garden and in all of my natural gardens I use no slug control at all. 


Sometimes checking out facts in google I come across something interesting. The story in wikipedia under the heading ‘famine food’ appealed to me!


18 comments:

  1. Great picture, that top one Roger.

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  2. I am always interested in reading about how others cope with their slug/snail population.
    When I installed my small wildlife pond last year - I made the consciensous decision to no longer use any form of slug deterrant natural or otherwise. There was no point in trying to attract other wildlife to then go on to attempt to eradicate another.
    This resolution didn't last very long, obviously the weather only seemed to create an explosion in slug population! I had to revert to using blue pellets. Like you I only use a minimal amount - no more than 2 or 3 positioned a bit away from the plant I do not want them to get a taste for.
    I've tried the beer traps - whilst they do attract the slugs - I agree that they also trap other insects/beetles.
    Eggshells, grit etc only seem to work for a very short time and these do not discourage the tiniest (mainly beige)slugs which have already positioned themselves right at the very heart of the plant, where there is rich pickings!
    Another theory I tried was a bark mulch - this seemed to harbour the slugs and the areas where I put it down had abundant mounds of eggs.
    I have tried in the past to leave rotting vegetation for them but did not find success there either.
    Interestingly enough, there are quite literally 100s of apparently fail safe tips/methods for slug/snail control available out there - unravelled copper scourers seemed to do the rounds last year.
    I usually began some sort of slug control on Valentines Day - the theory is to get them early enough thus there will not be so many for the rest of the year. Thus far, I have resisted and not offered anything. Having been working in the garden all week - I have found very little evidence of slugs but don't know if that is because the weather has been cold and the borders are very dry, unusual for this time of year up here!
    I suspect I've rambled on too much, so I'll end there.

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    1. I love your ramblings Angie,they express so well the dilemma that slugs give us, I think their absence at the moment is the low temperatures. I think I am more relaxed about their presence around my ponds than you, I just turn a blind eye. Actually I think I have so much wildlife including numerous frogs that there are very few slugs there.

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  3. Not so much a friend! I have a section about slugs and snails on my website too. When I was teaching we 'grew' snails and it was fascinating to see the tiny baby snails developing inside the transparent egg and to watch their feet rippling up the sides of glass tanks but boy were they smelly!

    One bit of useful information I find is that if a slug or snail has started nibbling a strawberry - leave the fruit in place as they will go back to the same fruit and nibble more rather than move on to a different fruit. Move the nibbled fruit and they just select a new meal.

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    1. Yes I think that is great advice. It applies in many other cases like wasps on apples, they tend to go back. If you throw the damaged fruit away, they start on another!

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  4. A super highway for slugs is a disturbing concept. I don't really have problems with slugs, I think we're a little too dry.

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    1. Not last year perhaps...
      Yes I am also normally dry in summer, Jason. I would say in the round that I do not have a problem with slugs either. As mentioned in another reply my garden has plenty of natural predators such as frogs and newts and it's really only in the veg garden and my greenhouse that I ever do any slug control at all. As to super highways please excuse my hyperbole.

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  5. There has been a lot written about slug control over the years, and much of it is completely contradictory. You can find evidence for practically any argument you care to put forward. Have you ever tried the Copper band idea? Even if it is effective, it is far too expensive for most people. I use blue pellets, but as you advise, in sparing quantities. The "sacrificial plant" principle is also quite attractive (I mean offering the slugs something even tastier than your brassica seedlings). I would propose the Chinese Leaves type of cabbage, which seems to me to be the most slug-attractive plant ever!

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    1. Thanks for this thoughtful response Mark - especially your sacrificial plant idea-a kind of bait. I know how slugs love chinese leaves!

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  6. I had so many problems with slugs last year, as I think most of us did in the wet conditions, that I'm without brassicas of any kind. They got the lot as seedlings. I've already had a slug encounter this year too. Some of my broad bean seedlings have been munched, and the culprit was there in full view, a huge, light brown slug. I've never used pellets of any kind, and I don't really want to now that we've got a dog, but I may have to resort to a few in the greenhouse if I'm to get my plants beyond the seedling stage.

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    1. Thats really bad luck Jo. I think I must be really lucky, broad beans seem to do better in my garden than any other vegetable. I never lose any to slugs and I do nothing against these pests when I sow. I direct sow my broad beans and they are never checked by transplanting. I am a little low on my brussels this year, I lost quite a few to cabbage root fly - you can't win them all!

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  7. I haven't tried it on my allotment yet, but apparently using a Scotchbrite type scouring pad as a collar around each seedling works the same way as eggshells or copper, as our slimy friends can't cross it. You can buy cheap ones in a market, and of course they would be re-usable in following years. I think I'm going to try it this year. We have a great many slugs and snails as our 'patch' is bordered by hedge on two sides. After rain they come rampaging out like the cavalry. I would love to encourage hedgehogs, as I understand they eat slugs, but to do so would be immoral as everyone else on the area uses blue pellets, putting poison into the foodchain.

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    1. It's frustrating when gung ho inexperienced gardeners misuse all these aids and for example they waste valuable materials like peat in a totally indiscriminate way whilst serious gardeners like yourself try and be responsible
      I would not have your patience to use the scouring pad but I am sure others will!

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  8. I believe that slug 'problems' are of our own making and stem from a seriously distorted perspective of 'what a garden should look like'. Orderly rows, clean soil and immaculately manicured lawns and hedgerows are so alien to nature that we create terrible distortions of balance - that all too critical component of natures stability. This is often compounded by our overpopulation with the consequence that a 'garden' can often be as tiny as a container or two. In such tiny portions, nature finds it near impossible to establish any sense of balance.

    When I took over my field, it had been used extensively as agricultural smallholding for many decades. I planted a third of it with wheat (for the chickens). It was a wet year and every ear was smothered with small grey keel slugs. my first stab at re-establishing a sense of balance came with the release of half a dozen Khaki Campbels. For weeks, their crops were gorged with a rich diet of slug protein. For the ducks to harvest the slugs, they had to be able to be active by first light, so they were left un-cooped - the local foxes soon dined well on recycled slug...

    At that point, my field was a typical wildlife wilderness - just barren cultivated soil. So my second move was to set up wildlife 'reserves', typically nothing more than piles of brash, wood, hedge trimmings and general slow to rot rubbish. I wanted to establish places for predators like ladybirds to overwinter. I also set up a number of hedgehog 'houses', along with some buddleia, ivy and nettle patches. Years on now, and I also have a number of totally wild patches that the neighbours think are shameful wastes of good growing land.

    Yes, I still have a few slugs and snails (even a few delightful banded snails) but nothing like the near monoculture of keel slugs that I inherited with the land.

    My lesson has been easy - nature is far too complicated for us to even begin to comprehend, if we try to fight it - we loose, so make room for nature within your gardens and try to see rubbish piles for the amazing value that they offer us. See the 'Brown Bin' as your enemy, put as much back into your garden as you can.

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    1. As ever your eloquent writing needs no comment from me!

      You would have liked the article in this week's New Scientist about hydra theory - the more heads you chop off the more grow. I thought of slugs
      I expect you liked the famine food story in the wiki link. Loved your phrase 'recycled slug'

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  9. Actually, I think I dined better on recycled slug than the fox did - those super rich duck eggs every day were amazing. Today, the bulk of the control is by Thrushes and Hedgehogs. I don't know how many 'hogs I have in the garden, but judging by the numerous tracks each morning in the dewy grass, there seems like quite a few.

    I missed the famine food story though, where do I find it?

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  10. The story is in the wikipedia link at the bottom of the article. Just click the pink writing 'wikipedia' When you get to wiki just scroll down until you find the title 'famine food'

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