A long black whip at the top of the cane may be whip smut. Bag the whip before it bursts, uproot and destroy the clump, and do not take setts from this field. If more than 10% of clumps are infected, do not keep the ratoon.
How to identify smut
Look for these symptoms, as listed by Tamil Nadu Agricultural University (TNAU):
- Whip: A whip-like structure 25 to 150 cm long grows from the top of the cane.
- Covering: At first the whip is covered by a thin silvery membrane, with black powder inside.
- Cane: Infected cane turns thin, with long internodes early on and shorter ones later.
- Clump: Especially in ratoon, side buds sprout heavily and leaves stay narrow and upright.
Why one clump can put the whole field at risk
According to the South African research body SASRI, an infected clump releases billions of spores. Wind can carry them to nearby fields, and rain and irrigation water spread them too. Spores infect sprouting buds and new shoots, so the period after planting and after harvest matters. Infected setts also take the disease to new fields. In dry soil spores can survive for at least 6 months.
What to do if you see a whip in the field
- Bag the whip: Do not shake it. Slip a gunny or plastic bag over it and close it gently. TNAU then advises keeping the bag in boiling water for 1 hour.
- Remove the clump: Uproot the whole diseased clump and destroy it by burning. Take care that whip powder does not fall on other clumps.
- Check again and again: SASRI advises checking the field every 4 to 8 weeks. New infected clumps can appear after a clean-up.
- Count: Count 100 clumps in different parts of the field and note how many are diseased. Your ratoon decision comes from this number.
Keep the ratoon or not?
TNAU advises against keeping the ratoon when infection is above 10%. That means if more than 10 of 100 clumps have whips, the field is not fit for ratoon. Even at lower infection, keep checking regularly. If the ratoon sprouts poorly, also read Poor ratoon sprouting in the cold.
When you clear the field, remove the old stubble thoroughly. SASRI says clumps left behind can regrow and become a source of infection later. It advises keeping the field empty for at least 3 months after the last regrowth is removed. If possible, irrigate the field two weeks before replanting so spores in the soil germinate and die.
What to watch for when taking setts
- Seed: Do not take setts from a smut-affected field at all. Take them only from a checked, healthy field.
- Hot water: TNAU gives hot water treatment at 50°C for 30 minutes or 52°C for 18 minutes. Keeping the temperature exact needs a thermometer and a proper tank. Ask your Krishi Vigyan Kendra where this facility is available.
- Variety: A resistant variety helps, but SASRI says it can still be infected under heavy disease pressure. Ask your agriculture university which variety suits your area now.
- Pigeon pea: According to TNAU, growing pigeon pea between the rows can reduce further spread.
Red rot is a different disease from smut. To identify it, read How to identify red rot. For pesticide choice, ask your local agriculture officer.
Questions and answers
How do I count 10% infection?
Count 100 clumps in different parts of the field. If more than 10 of them have whips, TNAU advises not keeping the ratoon.
Is it enough to just cut off the whip?
Cutting alone does not remove the infection in the clump, and the powder can fly while cutting. Bag the whip first, then uproot and destroy the clump.
Sources: TNAU Agritech: Sugarcane smut · SASRI: Managing smut in sugarcane
*Farmers' results are their own experience, not a guarantee. Results change with soil, water, weather and care.
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