Stem gall (coriander)
Swollen, twisted lumps on the stems and flower heads that leave the seed inside shrivelled and worthless — coriander’s defining disease where humidity runs high.
- Pathogen
- Fungus (Protomyces macrosporus)
- Favoured by
- High humidity, wet soil at flowering
- Affects
- Stems, branches, flower heads (umbels)
- Main risk
- Shrivelled, worthless seed in galls
Overview
Stem gall is caused by a fungus called Protomyces macrosporus. It infects the stems, branches and flower heads (umbels) of the coriander plant and makes them swell up into distorted, twisted lumps called galls. Where a gall forms on a flower head, the seed inside is shrivelled, empty and worthless — so even a plant that survives can lose most of its seed value.
The fungus thrives in high humidity and wet soil, especially around flowering time, which is exactly the stage when the crop is most valuable. Because there is no real cure once galls have formed, control depends mainly on preventing the disease before it starts — a resistant variety, clean treated seed, and not over-watering the crop as it comes into flower.
How to identify it
- Swollen, distorted, twisted lumps (galls) on stems, branches and flower heads.
- Parts of the plant bearing a gall twist and grow abnormally instead of straight.
- Seed inside a galled flower head is shrivelled, small and empty — it will not fill or sell as good seed.
- Symptoms usually show up around flowering, the stage that decides the whole seed crop.
What causes it and when
- A fungus, Protomyces macrosporus, that infects the growing stem, branch and flower tissue and makes it swell into a gall.
- High humidity and excess soil moisture strongly favour the disease, especially around flowering time.
- Over-irrigating the crop as it comes into flower is one of the biggest risk factors a grower controls directly.
- The disease tends to be worst in the main coriander belt in years or fields with consistently humid, wet conditions during flowering.
Cultural & organic control
- Grow a gall-resistant variety where one is recommended for your area — this is the single most effective defence against stem gall.
- Always start with treated, disease-free seed from a reliable source.
- Keep the crop on the dry side, especially at flowering — avoid over-irrigating, since excess moisture is the main trigger.
- Remove and destroy plants showing galls promptly so they do not carry the fungus over within the same field.
Chemical control
- There is no reliable cure once galls have already formed — the priority is stopping new infection, not treating existing galls.
- A fungicide seed treatment before sowing reduces the starting risk on fields with a history of this disease.
- Confirm the current recommended seed treatment for your area with your local Krishi Vigyan Kendra (KVK), since coriander has no strong in-season chemical control once the disease is established.
Prevent it coming back
- Choose a gall-resistant variety and use fresh, treated, certified seed every season.
- Avoid over-irrigation, especially through the flowering window, and improve field drainage where water tends to sit.
- Rotate coriander out of a badly affected field for at least one season, growing a cereal or another unrelated crop instead.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Varieties to consider
Named seed varieties whose resistance or susceptibility to this problem is documented on their own variety page.
Frequently asked questions
My coriander stems have twisted swollen lumps — what is it and can I still get seed?
That is stem gall, coriander’s most damaging disease in the main growing belt. Once a flower head is galled, its seed is shrivelled and worthless, so those particular heads are a loss. Ungalled parts of the same plant can still fill seed normally, but a heavy attack cuts overall seed yield substantially — there is no cure once galls have formed, so prevention next season matters more than trying to save this crop.
Can I spray something once I see galls forming?
No spray reliably cures a gall once it has formed. The disease is best stopped before it starts — with a gall-resistant variety, treated seed, and keeping the crop on the drier side, especially around flowering, since excess moisture is the main trigger for new infections.
Why does keeping the field a bit dry at flowering help against stem gall?
The fungus that causes stem gall needs high humidity and wet soil to infect the plant, and it does the most damage right around flowering — the stage that decides your seed yield. A few light, well-timed irrigations rather than heavy watering at flowering keeps conditions less favourable for the fungus, which is why coriander does better on the dry side at that stage.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.