Tortrix moth caterpillars stitch leaves together to provide a little shelter for themselves, and then they graze away unseen inside their little tent of leaves. They’re a regular problem for me on choisya and rosemary, but today I found one on a young lovage plant. They seem to favour the strongly aromatic plants, leaving most others alone.
The only way to deal with them, because they are hidden inside the leaves, is to nip the affected part out. If you open up the leaves they have stitched together the caterpillar will thrash around quite wildly in a bid to escape and find cover again: and then, you’ll quite likely drop it.
It amazes me that such a soft and juicy little caterpillar is able to pull together and then glue quite firmly tough, leathery leaves like those of choisya. But I’m not impressed enough to spare them!