Redcurrants bright red blisters on leaves

[Digeroo]

Redcurrants leaves going red.  I think it is an aphid but I cannot see the beasties.
Finally found one tiny little hard green lump on one leave.  Is this the culprit?
Pictures on google show lots of the little blighters. 

Anyway the question is what do you do about it?

[Digeroo]

[johhnyco15]

_http://www.gardenersworld.com/how-to/blister- ahid   try this link if it isnt a bad outbreak it should not effect yield  however gardeners world give chemical or organic ways of controlling it hope this helps

[Digeroo]

The link does not work but found this
http://www.gardenersworld.com/how-to/solve-problems/currant-blister-aphids/
Seems they sow their eggs and then go away so perhaps that is why I cannot find them.
It is more like this, so rather dramatic
http://www.gapphotos.com/images/LargeWebPreview/0560/0560465.jpg

[brownthumb2]

 I had the red blisters on few of my leaves last year as there weren't many affected I was able to remove the leaves and burn   Got rid of few of the population

[Digeroo]

So is it best to remove the blistered leaves to reduce the numbers of the critters?  I have dipped quite a few of the affected leaved into nettle tea.