Blackcurrant: new growth twisted, puckered or distorted

What it is likely to be on blackcurrant

1. Currant blister aphid

   Candidate 1very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Currant blister aphid
   • Agriculture and Horticulture Development Board — AHDB: Currant aphids

   Checked 2026-08-13

   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.

   Points towards it

   • · the distortion is caused while the leaf is still expanding, so it is confined to the spring flush and never appears on mature leaves
   • · pale aphids shelter under the blistered tissue, which is what caused it
   • · the blisters are raised puckered swellings — crimson on red and white currants, yellow-green on blackcurrant — rather than spots with edges
   • · it runs from April to early summer outdoors

   Argues against it

   • · damage on old leaves only cannot be this, because the mechanism requires the leaf to be expanding while it is fed on — this rules it out entirely.
   • · a surface coating is a mildew rather than a swelling of the leaf itself

   Check this next

   Turn a blistered leaf over. The redness is the plant's own response to feeding, so the underside of a fresh blister carries small pale aphids — and the blisters are raised and puckered rather than flat spots sitting on the surface. By midsummer the aphids have gone to other plants and the old blistered leaves simply stay as they are, which is why the bush looks worse than it is.

   What to do now

   In an established fruiting bush, nothing. The crop is unaffected, the damage is confined to spring foliage, and the new growth that follows midsummer is clean — spraying a currant in flower to prevent a cosmetic leaf blister is a poor trade for the pollinators it costs. On a young bush that is badly distorted, squashing the aphids by hand on the leaf undersides is proportionate.

   ·source

   GrowingHQ editorial positionhigh confidence

   A proportionality judgement rather than a horticultural claim, and the reason this rule was written: the differential kept offering treatments for a problem that does not need one.

   • GrowingHQ editorial synthesis — GrowingHQ

   Checked 2026-08-13

2. Powdery mildew

   Candidate 2common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Gooseberry — American gooseberry mildew
   • Agriculture and Horticulture Development Board — AHDB: Ribes — powdery mildew

   Checked 2026-08-13

   A white, floury coating on the upper leaf surface, most familiar on courgettes and cucumbers late in the season. Unlike most fungal diseases it does not need the leaves to be wet — it needs the roots to be dry and the air to be humid, which is why it arrives in a warm dry August.

   Points towards it

   • · a white felt over the youngest leaves and the tip is the cause of the distortion
   • · the fungus infects the expanding tip, which then fails to develop properly
   • · no insect is involved, which separates it from an aphid distortion

   Argues against it

   • · a colony inside the crumpled tip makes this an aphid problem

   Check this next

   Rub the distorted tip between finger and thumb. Mildew comes off as a white powder and leaves the leaf beneath stunted, cupped and often felted brown where the infection is older; on gooseberries the same coating goes on to the fruit and turns buff and rough. Aphid distortion has insects and stickiness and no powder. Frost distortion has neither powder nor insects and stops at a height across the whole bush.

   What to do now

   Cut out the affected shoot tips into clean wood and bin them rather than composting, working in dry weather. Prune the bush to an open goblet so air moves through the middle, since congested still growth is what the fungus needs, and avoid high-nitrogen feeds that push soft sappy tips. Water the ground rather than the foliage, and keep the roots evenly moist — dry roots in humid air is the combination that suits it best.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Powdery mildews — control

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on blackcurrant — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general new growth twisted, puckered or distorted page lists causes across all plants, and the Blackcurrant profile lists the problems it is prone to.