How to kill caterpillar

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1 hour ago, Flamedodger said:

Pretty much every species of UK butterfly has had a tough year this year. I’ve been photographing them for a couple of years and do the Big Count. 
They were so many more last year, the wet spring was a killer for so many insects this year. 
UK….no.1 for the most depleted wildlife on the planet

Sadly You are right and for that reason.

I do not use any weed killer only white vinegar when absolutely necessary 

Saying that I would use napalm or agent orange on next doors ivy if I could get away with it