[David Dickinson]

It seems to prefer Sedum telephium. Could it be Corn Borer? Does anybody else have the same problem? At first I thought it might be the same butterfly that has destroyed all the unsprayed Pelargoniums in the area and then moved onto my Lab Lab seeds. However, the grubs are very different, not like the Hairstreak-shaped grubs of the butterfly but much more like the classic caterpillar shape with greenish bodies and dark heads. Are there any natural remedies?

Couldn't photograph them as it was getting dark and they were very small. One to each stem. Despite their small size they had done sufficient damage to cause the stems to collapse at the point where they had bored in.

[MikeHardman]

David,

There are quite a few stem-boring larvae; could be lepidoptera or beetle.

Systemic insecticide seems worth a go.
But of course, part of the issue will be the local population, waiting to in-infest.
If the particular culprit could be indentified, maybe we could see if there is a known pheromone trap for it.

An aside:
There's a stem borer that goes for my Cupressus sempervirens, working along the twig towards the tip until its tunnel is the same size as the twig, whence the trig drops off. I expect other folks have noticed such twig-tip-drop. Next time, pick up the twig and look at the end. I bet you'll see a hemispherical hollow - the end of the tunnel.

Mike