The Icebergs are of the variety Maugli and have done exceptionally well in the polytunnel. In fact, this time a few days ago they were really looking the real deal. But then holes started appearing. Just a few small ones at first. I sprinkled some organic slug pellets around the lettuces, but the holes carried on, gradually increasing in size and frequency until some of the lettuces started to look a little ragged.

Research confirmed that these lime green loopers would, if allowed, grow up to be small white cabbage white butterflies. Not having grown lettuces particularly successfully before, I stupidly hadn't even realised that they would be targeted by cabbage whites.
As picking them off was not going to be effective, I decided to prepare a soap spray. Not ideal on salad leaves as it might scorch them and they would need a good wash before eating, but the best option available. I took to the interweb to remind myself of the best solution to mix up and very quickly came upon an alternative organic solution - flour!

The icebergs had snow on them!
Apparently, the caterpillars are supposed to eat the flour which causes them to bloat and die.
ed - if you're wondering how I've got scorching weather here when you've got clouds and drizzle, this post was written just before the lightning storm took out my broadband. Things have moved on a bit since then. As for the lettuces, the flour was quite effective, but not before the caterpillars had done enough damage to really spoil them. I even found one which had made a cocoon inside the lettuce.
I have some more seedlings on the go though. I'll net the next ones!