Friend or Foe

This last season the whole site was plagued with Cabbage White butterfly, and everyone seemed to suffer no matter what they did. I tried netting all the brassicas with, what I thought, was a narrow enough mesh to keep them out and prevent them laying eggs. However, the day I saw butterflies fluttering in and out of the netting at will, I knew my plan had been foiled and it could only be a matter of time before the caterpillars appeared.

It’s a strange irony that though allotment holders are typically people who appreciate the wonders of nature, they have to deal ruthlessly with it at times. It’s similar to the idea that a weed is only a plant growing in the wrong place, I suppose. One minute you can be enjoying watching these beautiful insects dancing about in the summer sun, and the next be chasing them like a lunatic, with a cane, as they try and lay their eggs on your precious cabbages.

Not that I'm of any religious persuasion that sanctifies the protection of life in all its forms or anything, but it was with a certain reluctance that I had to go round all the plants and destroy any eggs by hand. Funnily enough, I found the netting made the job much more difficult, and don’t think I’ll bother at all with it next season.

I thought I had got them all, then one day when focusing more closely on something strange on a particular plant, I realised with horror that I was looking at a seething mass of caterpillars! As I had decided to not use any insecticides, there was only one thing for it but to literally pick them all off and dispatch them. Not a pleasant job.

The Cabbage White season came and went, and I’d almost forgotten about them, when one day in the shed I noticed a caterpillar stuck to the roof. Ah, an escapee I thought, nicely settling down to pupate, and my first reaction was to destroy it and the others that were there. Then I noticed what I thought were a bunch of eggs attached to it, but something wasn’t quite right, caterpillars don’t lay eggs.


After some googling, the puzzle was eventually solved. The “eggs” turned out to be the tiny larvae of a small parasitic wasp called Cotesia glomerata, that spin a yellow silk cocoon around themselves.

In this picture you can just make out the wasp at the side of the caterpillar.


The wasp parasitizes the Cabbage White caterpillar, by laying it’s eggs in the caterpillar’s body. Then, like something out of a horror movie, the larvae feed on the living caterpillar and eventually emerge to spin their cocoons. What’s more bizarre is that they don’t eat the caterpillar’s vital organs, so that the life of the host is prolonged as long as possible, and they even control the host’s behaviour by causing it to stay with the cocoon cluster.

So now, any that I find in the shed, are left for my new found little friends to do their gory job on.

Isn't nature just wonderful!!!