White rust
Shiny white raised pustules under the leaves and swollen "stag-head" flower stalks that bear no pods — a cool, wet-weather crucifer disease.
- Pathogen
- Albugo candida (fungus-like)
- Spreads by
- Air/rain-splashed spores; seed & debris
- Favoured by
- Cool, humid, dewy, wet weather
- Main risk
- Stag-head flower stalks bear no pods
Overview
White rust, caused by the fungus-like organism Albugo candida, is a common disease of mustard/rapeseed and other crucifers (radish, cole crops). On leaves it forms shiny, white to cream, raised pustules, mostly on the lower surface, in groups; the tissue above may yellow. Its most damaging phase is when it infects the growing point and flower stalk, which then swells, thickens and distorts into a green, curved, malformed "stag-head" that bears no healthy flowers or pods.
Because the stag-head phase directly destroys the pod-bearing parts, a heavy attack causes real yield loss in mustard. White rust often occurs together with downy mildew on the same distorted stalks. It is favoured by cool temperatures, high humidity, dew and wet weather, and it carries over on infected debris and seed. Management combines resistant varieties, clean/treated seed, roguing stag-heads, field sanitation and a protective fungicide where the disease is expected.
How to identify it
- Shiny, white to cream, raised pustules in groups, mostly on the underside of leaves, with yellowing above.
- Swollen, thickened, curved, malformed "stag-head" growths where the flower stalk/growing point is infected.
- Stag-heads bearing no healthy flowers or pods — the main yield-robbing phase.
- Often together with downy mildew on the same distorted stalks, in cool, humid, wet weather.
What causes it and when
- The fungus-like organism Albugo candida, spread by air- and rain-splashed spores and carried on infected debris and seed.
- Favoured by cool temperatures, high humidity, dew and wet weather during the crop.
- Infects leaves first, then the growing point and flower stalk to form stag-heads.
- Carries over on infected crop debris and seed, and often accompanies downy mildew.
Cultural & organic control
- Grow resistant/tolerant varieties and use clean, healthy (treated) seed.
- Rogue out and destroy stag-heads and infected debris before spores spread.
- Rotate with non-crucifer crops and remove cruciferous weeds that host the disease.
- Avoid dense stands and manage for a drier, better-ventilated canopy.
Chemical control
- Treat seed with a recommended fungicide (e.g. a metalaxyl-based dressing) to reduce early infection.
- Spray a CIB&RC-registered fungicide (e.g. metalaxyl+mancozeb or mancozeb) protectively where the disease is expected, before stag-heads form.
- Time sprays to cool, humid, wet spells and cover the lower leaf surface where pustules form.
- Confirm the current product, dose and timing for your crop with your local KVK.
Prevent it coming back
- Base the crop on resistant varieties, clean/treated seed and crop rotation.
- Rogue and destroy stag-heads and debris, and control cruciferous weeds.
- Plan protective sprays for cool, humid spells in fields with a history of white rust.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Frequently asked questions
My mustard flower stalks are swollen and distorted with no pods, and the leaves have white pustules underneath. What is it?
Those shiny white pustules under the leaves and the swollen, curved, malformed "stag-head" flower stalks that bear no pods are white rust (Albugo). The stag-head phase is what costs yield, because those stalks never set pods. It is worst in cool, humid, wet weather and often comes with downy mildew. Grow a resistant variety, use treated seed, rogue out stag-heads, and spray protectively where it is expected.
Is white rust the same as the yellow/brown rust of wheat?
No — despite the name, white rust is a different kind of organism (Albugo candida, a fungus-like oomycete) from the true rust fungi that cause wheat yellow and brown rust. White rust makes shiny white pustules on crucifers like mustard and forms distorted stag-head flower stalks, and it is favoured by cool, wet, humid weather. It is managed with resistant varieties, treated seed, roguing stag-heads and metalaxyl-type fungicides, rather than the triazole sprays used for cereal rusts.
Why is the stag-head stage so damaging?
Because white rust infecting the growing point and flower stalk turns them into swollen, distorted "stag-heads" that cannot produce healthy flowers or pods. Since pods are where the yield is, every stag-head is lost yield, and a heavy attack that distorts many flower stalks cuts the mustard crop significantly. That is why control aims to protect the crop before flowering and to rogue out stag-heads, not just to reduce leaf pustules.
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.