BT (Bacillus thuringensis) is the perfect killer for caterpillars - in fact it's so targeted that they've bred strains to hit particular caterpillars.
I got good results from it about 10 years ago (luckily the last time I had stripped gooseberries), but it seems to have disappeared from the shops. This makes me wonder if the broad-spectrum type I used is no longer available.
Perhaps someone can throw some light on this? I read the Wiki article but I'm still not sure what it means for those of us who are amateurs.
I think professionals can still get it - maybe you have to know the actual species to get the right stuff?
PS. All my old stocks of derris/rotenone have degraded (confirming it's still a lot safer for the environment than neo-nics) and it's very hard to source now because it's been "linked" to Parkinsons** - hmmm... (read the site www.dhmo.org
together with the definition of "cui bono").
**I suspect that's mainly because we were encouraged to 'splash it on all over' - one of the justifications for the latter being that many jungle tribes have been eating derris-stunned fish for millennia - something that still makes me think it's preferable to new stuff that was only tested "five minutes last week". If used with care...