A Third Ratoon That Smells of Alcohol: Diagnosing a Collapsing Cane Field
On 12 September a supervisor inspects 3.2 hectares where the crop is a third ratoon of Co 0238, raised from the farmer's own seed material for four consecutive cycles. About 35% of the area shows irregular patches of canes drying from the top; stalks are hollow and light, and on splitting a cane there is a sour, alcoholic smell with reddish discoloration and whitish patches inside. Several clumps have collapsed at the base. Neighbouring fields of a different variety are healthy. Soil test: pH 8.4, organic carbon 0.38%, available zinc 0.42 ppm. The farmer has applied three irrigations in the last month and 2 quintals of urea per hectare after the first symptom appeared. He asks whether the trouble is water shortage, top borer or fertiliser, and wants to keep the crop for one more ratoon because the mill's arrears make replanting unaffordable. The village has 40 other cane growers, several of whom source seed from this same field.
1. Diagnose the problem and state, with reasons, why each of the farmer's three hypotheses is or is not supported by the symptoms.
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Diagnosis: red rot (Colletotrichum falcatum), with a secondary zinc constraint.
The decisive signs are internal: reddish discoloration broken by whitish patches, a sour alcoholic odour, hollow and light stalks, drying in irregular patches, and collapse at the base. These are the textbook expression of red rot, and every one of them is a symptom of tissue breakdown by the fungus.
Why not water shortage: drought stress is uniform across a field, shows leaf scorching and rolling, and never produces a sour smell, hollow pith or internal reddening. This field has had three irrigations in a month.
Why not top borer: borers produce dead hearts in the young crop, exit holes and frass in the grown cane, and a reddish tunnel only along the bore path - not diffuse internal discoloration with white patches across the whole stalk.
Why not fertiliser alone: the 2 quintals of urea applied after symptoms cannot create them; excess nitrogen causes lodging and soft growth, not sour, hollow stalks.
Predisposing factors: a variety known regionally for red rot susceptibility, four cycles of own-seed use, a third ratoon, and heavy irrigation - plus pH 8.4 with zinc at 0.42 ppm (below the ~0.6 ppm sufficiency mark), which explains the pale younger leaves. The field is also the village's seed source, which is the most dangerous fact here.
2. The farmer cannot afford to replant immediately. Recommend a rehabilitation plan sequenced over two to three seasons, and justify the order of priorities.
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Season 1 - at harvest (cost: mostly labour). Do not take a fourth ratoon. Mark the 35% affected area, rogue out and burn those clumps away from the field; buried trash keeps the fungus alive. Take the healthy cane to the mill but keep none of it as seed.
Season 1 - after uprooting (cost: moderate). Deep plough. Apply 10 t/ha farmyard manure and 25 kg/ha zinc sulphate; the pH 8.4 and 0.42 ppm zinc explain the pale leaves and will otherwise cap the next crop. Sow dhaincha and incorporate at 45 days, or take a short-duration moong - both cost far less than a cane crop and lift organic carbon from 0.38%.
Season 2 - planting (cost: the big one). Buy certified seed from a recognised nursery, not from this field, and choose a variety with demonstrated field resistance in the local zonal trial rather than Co 0238 here. Treat setts with a carbendazim dip (0.1%) or moist hot-air treatment, and plant only where there is a drainage outlet.
Priority logic: stopping the inoculum (rogueing, no ratoon, no own seed) comes first because it is cheap and prevents spread to 40 neighbours; soil correction comes next because it is the constraint on the next crop; seed purchase is the largest expense and can wait until the plot is clean.
3. Should the farmer be allowed one more ratoon to tide over his cash problem? Answer as the supervisor who must also protect the neighbouring growers.
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No - and the cash argument should be answered with a cheaper alternative, not with permission.
Three reasons. First, yield: a third ratoon is already well below a plant crop, and on a red-rot-affected plot the surviving clumps will give a thin, uneven stand; the extra ratoon earns little while consuming the plot. Second, epidemiology: the field is the village's seed source and sits among 40 growers; a fourth ratoon keeps a live inoculum reservoir through the next season, and setts from it would carry the fungus to new fields - the supervisor's duty here is to the wider supply chain, not only to one holding. Third, the mill's own interest: cane from an infected plot lowers recovery and creates disputes at the gate.
The cash problem is real and should be met directly: a moong or dhaincha rotation returns cash or nitrogen within three to four months, whereas a fourth ratoon locks the land for twelve; the society can route the farmer to seed subsidy or a society-linked seed plot; and the mill's arrears case can be taken up separately on the payment calendar. The supervisor should record the field as infected in the society's register so that no setts leave it.