I think I mentioned the dreaded lupin aphid a while ago in a lupin post. I seem to have become a bit obsessed over the lupins this year but they have been so good, and provided such an unending feast for the snails that I feel justified. I had hoped that this nasty pest had not made it to Ireland yet but my weekend visit to Glasnevin Botanic Garden proved my optimism unjustified. I was wandering around the order beds and got to a nice clump of tree lupins and there it was, larger than life.
Like all aphids, this one sucks the sap from the plant and breeds at a ridiculous rate. What makes it a bit different is that it only attacks lupins and it seems to absorb some toxins from the plants that render it more or less immune to being predated by ladybirds or other insects that usually eat aphids. And as well as being bigger than most aphids it is also almost ‘aggressive’ and wiggles about in an alarming fashion (as do other aphids to a lesser extent) when it feels threatened. It is American and was first found in the UK in the 1980s. In fact I am sure it was first found at Kew Gardens and I was there when it was first discovered. Anyway it is established now and is a serious pest. It will feed on leaves and shoots but is particularly troublesome on the flowers stems where it can be present in such huge numbers that it kills the flower buds.
I do not like spraying but this is one pest I would not hesitate to spray since there is no natural control. You could rub off any that you see on small flower stems but once they start to elongate this is impractical. If your lupins have not flowered or are dying look to see if you have this revolting little sucker on your plants.