I have two Lupin plants next to each other in my front yard:
They are both Russell hybrids, both grown from seed and planted there at the same time in Spring 2009. The one on the left is healthy, but recent growth on the one on the right is stunted and deformed. The leaves are smaller, with narrower leaflets, and there are large gaps between individual flowers on the spikes.
I don't see any sign of insects on the affected plant (or on nearby plants, which include roses, lavender, Lithodora and Dianthus).
If it's any clue, I had several other Lupins near that spot that didn't grow this year, but that may be because it's been a colder than usual Spring here (Pacific NW, USA).
Is this curable? If not, should I dig out the affected plant? Can I replace it -- and the ones that didn't grow this year -- with more Lupins, or should I plant something else?