Courgette: new growth twisted, puckered or distorted

What it is likely to be on courgette

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

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 courgette — 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 Courgette profile lists the problems it is prone to.