Just a quick interlude from a book I recently finished reading. It wasn’t a gardening book by any means, but in one tongue-in-cheek section the author describes the behaviour of a nematode, Heterorhabditis bacteriophora, that is parasitic on insects but has a symbiotic relationship with a bacteria. I mention it here because the section refers to gardeners, because the worm is a bit of a gardener itself and because it made me smile.

Isn't it cute? This is a different one: Necator Americanus

H. bacteriophora has taken up farming of sorts.  As it grows, it  nurtures a particular bacteria in its gut. Once it reaches the third of its four juvenile stages, it sets out to find a ‘host’ insect. The worm enters the insect – through an orifice, or by breaking in through the insect body – and makes its wormy way to the insect’s body cavities. When it’s found a nice spot, it ‘plants’ the bacteria (ejecting them by vomiting or defecating, in case you weren’t enjoying this enough.) The released bacteria get to work on replicating – both feeding the growing nematode and killing the host. Once that’s done, our nematode friend gobbles up both its herd of bacteria and the insect corpse that the bacteria have kindly helped digest, before laying eggs so that the whole merry cycle can continue.

Since reading about this process, I’ve also learned that many of the eggs hatch inside the mother nematode, and the youngsters destroy the mother as they grow.

The author concludes: “Such natural means of pest control are preferred to chemicals by many gardeners who pride themselves on their sensitivity.

None of the animals involved in these extraordinary patterns of behaviour has a brain of course. *

*Except perhaps the gardeners”

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  • You may have used the little fellas to combat pests such as Asparagus beetle or weevils.
  • The book is about Caenorhabditis Elegans, which you might find in your compost heap. Elegans is named for its graceful undulating movement, and “lives in tranquil obscurity underground, parasitising nothing, eating only bacteria and slime mould.”
  • Other fascinating trivia on nematodes from the book: “A healthy worm defecates about every 45 seconds all its life.” 80,000 species of nematode are known but there may be 10 or 100 times more. Of the known, one lives in seals’ kidneys and can grow to 40″ long and “three  species can live in the rectum of the American cockroach.”
  • The book is called In the beginning was the worm. Finding the secrets of life in a tiny hermaphrodite, by Andrew Brown. It really isn’t a gardening book. It’s about the decades of study of C. elegans and about the scientists who did the work – work which had a huge impact of modern biology and on the sequencing of the human genome. I loved it: it’s written passionately, bringing in all sorts of different insights, with some wry humour and well-drawn character studies, and some sections of beautiful prose. I think it’s generally accessible, though coincidentally I read the first sections on genetics just after some study on the subject, so I don’t know how I’d have found it before. There are fascinating reflections on what drives scientists; the funding of scientific research; independence of thought, the commercialisation of knowledge and on what it means to be human. All of this makes it a rollicking good yarn despite a long middle section on who did what when, which seemed to lose some focus and structure, as well as some shoddy editing: perhaps there was a rush to get it out after the worm scientists received their Nobel Prize.
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I’ve been working long hours lately, so had planned a quiet Friday night in to recover myself. Instead, I have been on a murderous rampage.

Rest in peace, little bastards

Rest in peace, little bastards

When we moved here, back in February, the owner had left their beer-traps in the garden for us. That should have been a sign.

I gave it a go for a bit of fun, though father-of-frugilegus has always been cynical about their effectiveness. The first morning I checked the traps I counted 50 corpses before I concluded the total was ‘a lot’. That should have been a sign.

Despite that body-count, every seedling I planted in the beds disappeared overnight, the only indication it had ever existed a memorial trail of slime. I took that as a sign.

I ordered nematodes after that, and I have to say they were pretty effective. After a week, some seedlings survived. They certainly didn’t thrive, but the old nibbled stalk was actually visible here and there.

I kept up the slug-traps, trying old orange juice that had been lost in the back of the fridge instead of beer, and shook a few bodies into the compost bin once a week. I sprinkled some coffee grounds around seedlings every now and then. Though nematodes are only effective for about six weeks, I thought I must have taken out the hordes, and could control the rest with various fermented juices.

So, I planted out borage and strong cucumber plants. I positioned a climbing frame for the cucumbers to play on and, that night, dreamt of their fruit. The next morning, I went to welcome them to their first new day, and found just a few slimy stalks. That should have been a sign.

Friends or foes ... or utter bastards?

Friends or foes ... or utter bastards?

Still,  I was distracted by compost. The bin in the garden is not a good one, and when we moved in was full of organic matter that showed no interest in decomposing. I had given it a stir, added lots of brown matter and the contents of a bokashi bucket, then later a few worms, in the hope of getting it going. Things were looking good. An ecosystem developed: woodlice, wriggly things, beetles and the odd snail. I smiled on it benevolently, thinking that a wriggling bin is a healthy, decomposing bin.

Just as a weed is only a plant in the wrong place, I decided a snail is only an evil murderous bastard when it is in the wrong place.

Pah!

A compost bin is no more than a base from which vast hordes are unleashed under cover of darkness. It provides a mollusc with snacks during the day, but one mustn’t eat too much in the bin – one must save oneself for the night raids on pots of beans, tender cucumber shoots, and if one’s feeling adventurous, following the trails of shelled-scouts and slimy outriders into the herb bed.

Tonight it rained. Though the young basil I put out might find it a bit of a shock, on the whole it was welcome because the water butt is empty and the lawn is sulking (the lawn is a whole other story). I wandered out with the torch, thinking vaguely that I could check whether it was snails nibbling at the runner bean bucket.

But, upon finding a full-scale attack underway I was overtaken by bloodlust. Arming myself with a plastic bag on my hand, I grabbed and dropped, grabbed and dropped, each victim clunking into my bucket of water. Haha!

For the pernicious fault of gluttony, as you can see, I'm prostrate in this rain.

For the pernicious fault of gluttony, as you can see, I'm prostrate in this rain.

I can’t kill beetles, but it seems I can kill molluscs.

Though apparently not that easily. Putting snails in cold water doesn’t work. They squirm about and take turns to crawl on each other and then crawl out. It seems I should have used very hot water. An hour ago, I’d have said I wouldn’t have the stomach for it, but seeing as I’ve spent much of my Friday night sprinkling salt on antennae as they break the surface like little periscopes I don’t know if that is true any longer. I’ve never fancied salting slugs before, and it was expensive salt too, but none of that bothered me for a second when I found a speckled slug making a break for freedom. Later, overtaken by guilt, I poured in a can of beer too. So some died horrifically, but hopefully others died happy.

Tomorrow, more nematodes. And a new zero-tolerance policy. They had their chance with the compost bin and they’ve blown it.