Currant blister aphid
Raised puckered blisters on currant leaves — crimson on redcurrant and whitecurrant, yellow-green on blackcurrant — with pale aphids sheltering on the undersides. It looks alarming and like a disease, and it is neither: the aphids leave for other plants by midsummer, the fruit is unaffected, and the blistered leaves stay blistered because the damage was done while they were expanding.
Caused by: Cryptomyzus ribis · also called currant leaf blister, red blister on currant leaves, leaf-curling aphid
Described view
Blackcurrant foliage with the honeydew shine visible on the upper leaf surfaces, and the leaves turned to show the two aphids responsible: ordinary green aphids massed along a stem, and the currant blister aphid causing raised red puckered blisters with the insects sheltering in the hollows beneath
What brings it on
Feeding on the expanding leaves in spring distorts the tissue as it grows, so the blisters appear on new growth and stop appearing once the aphids migrate away in early summer. The colour is a plant response to the feeding rather than a pigment of the pest.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Currant blister aphid
- Agriculture and Horticulture Development Board — AHDB: Currant aphids
Checked 2026-08-13
Usually seen: April, May, June
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Not worth preventing on a fruiting bush. The cosmetic damage is confined to spring foliage, the crop is unaffected, and a spring insecticide applied to a flowering currant is a real cost to pollinators for no gain in fruit.
source
GrowingHQ editorial positionhigh confidence
A judgement about proportion rather than a horticultural fact, and the reason this record exists at all — the differential kept offering treatments for it.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13
Dealing with it once it is there
- Nothing, in most gardens. Where a young bush is badly distorted, squash the aphids on the leaf undersides by hand or pinch out the worst shoot tips; the plant grows out of it as soon as the aphids leave.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Currant blister aphid — control
Checked 2026-08-13
Widely repeated, and not supported
Recorded so GrowingHQ can address them. These are not alternative approaches — they are things the evidence does not back.
“Red blisters on currant leaves are a rust or a virus.”
The colour comes from the plant's own response to aphid feeding on expanding tissue. Turning a blistered leaf over and finding aphids settles it, and no fungicide has any part to play.
Horticultural consensusCommonly said, not supportedmoderate confidence
- Royal Horticultural Society: Currant blister aphid
Checked 2026-08-13
What it affects
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.