Woodlice normally only eat decaying plant matter and tiny seedlings if they are really hungry. They lack the strength of jaw to chew Lupins. Usual culprits are snails.

Hmmm.... Would you advise slug pellets then? I don't normally use those as it seems cruel.... I have no other ideas though!

Doesn't look like snail damage to me. The bites are rather distinctive, but not sure of what. Is there a sawfly larva that feeds on lupins?

I can see what look like tiny white beads on the leaves towards the left side of the picture, are they just aphids? and also something small and brown on the central stem, near the top, though that may be just some plant debris. There's no sawfly that I know about which targets lupins specifically - things they're prone to are fungal infections, viruses and aphids.

Could be bird damage, after the insects on it.

I looked over the plant and didn't find any pests. The white is damage, not anything living... the brown is a dead bit of flower bud.

It must be something that comes and goes as opposed to aphids and the like as there has been nothing there every time I've looked!

Looks suspiciously like caterpillar damage to me. I would go out with a torch at night, and see if you can catch them in the act.

I've just noticed that whoever the culprits are, they've stripped the crown of one of my emerging lillies - AND the new foliage of my Clematis......

Sounds as if there is a night flying/crawling insect in your garden. The next suspect could be vine weavil but I am not too sure about that either. Tug has the right idea, go out there after dark with a torch and see if you can spot anything. Make up a suitable story for the neighbours first or organise a bug hunting party :-)))

Looks like a night raid is in order then......

I'll report back tomorrow! :-)

Think you are right about woodlice. I have lupins that keeled over and have leaves just like photo. The stems have got dark "wounds" which go through to centre of stem. I cut stem to examine and lo and behold I found nests of woodlice with their larvae inside. Don't know how to get rid of them though.

Hi, I’m not sure how old this post is but I thought I would answer anyway in case anyone else stumbles across your question that is also looking for the same answer. Wood lice 100% eat the leaves of lupin. I went out to my mini greenhouse this morning quite early & although it was daylight and I saw about 15 of them on one lupin stem and they had munched almost all of the leaves. I moved them on and I hope they don’t return again by morning tomorrow