Cucumber: new growth twisted, puckered or distorted

What it is likely to be on cucumber

1. Powdery mildew

   Candidate 1common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: 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

   • · mildew infects expanding tissue and puckers it as it grows, leaving a white film on the distorted surface
   • · only tissue that was still expanding when infected becomes distorted
   • · powdery mildew is favoured by dry roots, unlike most fungal diseases

   Argues against it

   • · honeydew means a sap-feeding insect is present, and mildew produces none. Sticky distorted tips are an aphid problem — this rules it out entirely.

   Check this next

   Look for a white powdery film on the puckered surface, and open the tip to check for insects. Mildew leaves a coating and no animal; aphids leave an animal and something sticky.

   What to do now

   Improve airflow, keep the roots evenly moist — dry roots make it worse — and remove the worst-affected shoots. Any fungicide must be approved for the crop and used exactly as its label directs.

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Powdery mildew — control

   Checked 2026-08-13

2. Powdery mildew

   Candidate 2very common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: 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

   • · the white bloom appears on the leaf surface before the growth distorts
   • · powdery mildew is worse on a plant short of water at the root, unlike most fungi

   Argues against it

   • · insects on the tip point at aphids distorting it instead

   Check this next

   Rub the white coating with a finger. Powdery mildew wipes off and leaves green tissue beneath, which distinguishes it from anything structural — and on cucurbits it is the plant's ordinary end-of-season condition rather than a catastrophe, appearing on the oldest leaves first from midsummer. Distortion of the new growth means it has reached the tip and the plant is nearly finished.

   What to do now

   Water the roots generously and consistently and keep the foliage dry — powdery mildew on cucurbits is driven by root dryness, not by wet leaves, which is the reverse of most fungal problems. Remove the worst leaves to improve airflow and accept the rest: a plant that reaches September with mildew has usually done its job.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Powdery mildew — control

   Checked 2026-08-13

3. Aphids

   Candidate 3common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Aphids
   • Agriculture and Horticulture Development Board — AHDB: Protected crops — aphids

   Checked 2026-08-13

   Sap-feeding insects that cluster on soft growing tips and leaf undersides, distorting new growth and leaving sticky honeydew that blackens with sooty mould. Most garden infestations are transient and end when predators catch up.

   Points towards it

   • · under glass the aphid breeds all year without the predators that would hold it outdoors, so populations reach distorting levels
   • · colonies sit on the soft growing tip, and the leaves that unroll from it come out cupped and puckered
   • · green or pink colonies at the tip with honeydew on the leaves below is the whole picture
   • · soft sappy growth from generous feeding is what they prefer, and no event is needed for a colony to build

   Argues against it

   • · webbing on a greenhouse plant means red spider mite, which mottles and bronzes leaves without cupping the growing point
   • · an outdoor plant has the predators that keep this below the level where growth distorts

   Check this next

   Look at the growing tip with a hand lens and check what the underside of a mid-height leaf feels like. A greenhouse aphid colony sits openly on the soft tip — green, pink or black, moving slowly, with shed white skins caught in the honeydew — and the leaves unroll cupped and glossy from the sugar. Then rule the other greenhouse suspect out: run a finger under a leaf, and if it comes away with fine webbing and the leaf looks sandblasted rather than cupped, it is red spider mite and the answer is humidity rather than aphids.

   What to do now

   Wash the colonies off the tips with a jet of water or squash them by hand, twice a week until they stop reappearing, and ease off high-nitrogen feeding while you do it — soft growth is what they are on. Introduce the parasitic wasp Aphidius or hang yellow sticky traps if the greenhouse is warm enough for biological control to work. Ventilate on mild days so hoverflies can get in. The cupped leaves already made will not flatten out, so judge the result on the leaves that come next.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Aphids — biological control under glass
   • Agriculture and Horticulture Development Board — AHDB: Protected crops — aphid biocontrol

   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 cucumber — 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 Cucumber profile lists the problems it is prone to.