Smut (cereals)
Grain or earhead replaced by a mass of black, sooty spores — mostly carried on the seed, so seed treatment is the key control.
- Pathogen
- Smut fungi (Ustilago and allies)
- Spreads by
- Infected seed; soil-borne spores
- Favoured by
- Sowing untreated, infected seed
- Main risk
- Earheads/grain turned to black spores
Overview
Smut is the common name for several related fungi that attack the grain-bearing parts of cereals — loose smut of wheat and barley, and grain, head and covered smuts of sorghum, bajra and maize. Instead of healthy grain, the affected earhead or cob is filled with a mass of powdery black spores (in loose smut the whole earhead is turned to a naked mass of dark spores that blows away, leaving a bare stalk).
Most cereal smuts are seed-borne or soil-borne: the fungus travels on or inside the seed, or survives in the soil, and infects the young plant or the flower, showing up only at earhead stage. Because the loss is a direct loss of grain and the fungus is carried on the seed, the standard control is treated seed plus resistant varieties — an untreated smutty seed lot re-sows the disease every year.
How to identify it
- At earhead or cob stage, healthy grain replaced by a mass of powdery black or brown spores.
- Loose smut of wheat/barley: the whole earhead becomes a naked, sooty black mass that blows away, leaving a bare central stalk.
- Grain/head smuts of sorghum, bajra and maize: individual grains or the whole head swollen into smut galls or spore sacs.
- Only a proportion of tillers/plants affected — the loss equals the smutty heads, which produce no grain.
What causes it and when
- Smut fungi carried on or inside the seed (loose smut of wheat is inside the embryo), or surviving in the soil as spores.
- The fungus infects the seedling or the flower and stays hidden inside the plant until it replaces the grain at heading.
- Sowing untreated seed from an infected crop is the main way it carries over and spreads from year to year.
- Different cereals have different smut species, but the seed-borne behaviour and control are similar.
Cultural & organic control
- Always sow certified, disease-free seed from a clean, smut-free crop.
- Grow resistant or tolerant varieties where available — the cheapest long-term control.
- Rogue out and destroy smutted earheads before they burst and shed spores over the crop.
- For loose smut, the traditional solar (hot-water/sun) seed treatment reduces the embryo-borne fungus where recommended.
Chemical control
- Treat the seed before sowing with a CIB&RC-registered systemic fungicide (e.g. carboxin or tebuconazole seed dressing) — this is the single most effective step.
- For seed-surface and soil-borne smuts, a protectant seed dressing (e.g. carboxin + thiram type) is used at the recommended dose.
- There is no useful foliar spray once the earhead is smutted — control is decided at seed treatment.
- Confirm the current seed-treatment product and rate for your crop with your local KVK.
Prevent it coming back
- Make treated, certified seed and resistant varieties the routine — never re-sow saved seed from a smutty crop untreated.
- Rogue smutted heads early each season so they cannot re-charge the field with spores.
- Keep records of which lots and fields were affected and prioritise clean seed there.
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 wheat earheads have turned into black powder. What is it?
That is loose smut — a seed-borne fungus that replaces the whole earhead with a mass of black spores, which blow away and leave a bare stalk. Those heads produce no grain. It cannot be cured this season, but you prevent it by sowing certified seed treated with a systemic seed-dressing fungicide (e.g. carboxin or tebuconazole) and growing resistant varieties.
Why is seed treatment so important for smut?
Because most cereal smuts travel on or inside the seed — loose smut of wheat is carried inside the embryo. If you sow untreated seed from an infected crop you re-sow the disease every year. A registered systemic seed-dressing fungicide reaches the fungus in or on the seed and stops it before it can infect the plant, which is why it is the single most effective control.
Can I spray to control smut once I see black earheads?
No. Once the earhead is smutted the grain is already lost and no foliar spray helps. Smut control is decided at sowing, by treating the seed and using resistant varieties. If you see smutted heads, rogue them out and destroy them before they shed spores, and make sure next season’s seed is certified and treated.
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.