Currant blister aphid (Cryptomyzus ribis). The yellow-green blood blister aphid has a round shape and causes the red ‘blisters’ on the leaves of currants. White, red and black-currants can all be affected. In severe infestation, the leaves yellow and shrivel. The Currant blister aphid secretes honeydew that makes leaves, berries and branches sticky. Sooty dew easily forms on the honeydew.
The Currant blister aphid overwinters as an egg on the branches of currants.
Lacewings, ladybird, parasitic wasps and hover flies are among the natural enemies of the Currant blister aphid.
Difficult to to control; as soon as the red blisters become visible, the harm is already done and the currant is covered in honeydew. Cut away infested leaves.