Red Rot Explained: How Sugarcane’s ‘Cancer’ Turned India From Exporter to Importer

Cut open a healthy sugarcane stalk and its flesh is pale, wet and packed with juice. Cut open one infected by red rot and the picture changes dramatically. The tissue turns brick red, broken by white patches. The stalk begins to dry. Its juice ferments. In severe cases, the cane collapses before it reaches the mill.

The disease is so destructive that agricultural scientists call it the “cancer of sugarcane”.

That cancer has now entered India’s inflation story. Union Consumer Affairs Minister Pralhad Joshi has blamed red rot and El Niño conditions for a drop in sugar production, as retail prices rise before the festival season. The Centre has responded by permitting the duty-free import of one million tonnes, or 10 lakh tonnes, of raw sugar until October 31.

India still has enough sugar to meet its stated annual requirement. Joshi said domestic consumption is around 280 lakh tonnes and stocks provide a surplus of 20-25 lakh tonnes. Then why is a country known for exporting sugar suddenly importing it? How can a fungal disease infect an industry stretching from farms and mills to ethanol pumps and mithai shops? And is red rot an Indian outbreak or part of a wider global sugar squeeze?

Here is what we know.

What exactly is red rot?

Red rot is a fungal disease caused by Colletotrichum falcatum. It attacks sugarcane, particularly its stalk, and interferes with the movement and storage of water and nutrients inside the plant. Early infection can be difficult to detect from the outside. Leaves may lose colour, droop or develop red streaks along the midrib. The top of the plant can wither. By the time the cane begins drying visibly, the fungus may already have spread through the stalk. Its unmistakable signature appears when the cane is split open: reddened internal tissue interrupted by horizontal white patches. As the infection advances, the stalk shrivels, loses weight and may produce a sour or alcoholic smell because its juice has started fermenting. That internal destruction explains the “cancer” comparison. Red rot does not merely blemish the crop. It eats into the part of the plant from which sugar is extracted.

How does it reduce sugar production?

A mill needs two things from sugarcane: weight and recoverable sugar. Red rot can damage both. An infected stalk may become lighter as it dries. The fungus also consumes or degrades the sucrose stored inside it, reducing the amount of sugar a mill can recover from every tonne of cane crushed. A field may, therefore, appear to contain standing cane while producing far less commercial sugar than expected. If severely infected stalks die before harvest, the farmer loses the crop and the mill loses its raw material. Research published in the Journal of Sugarcane Research by scientists associated with the ICAR-Sugarcane Breeding Institute describes red rot as a disease capable of causing serious field losses. It also warns that the pathogen can develop new variants, or pathotypes, which may break through the resistance of previously dependable cane varieties. That ability to change is what makes red rot particularly difficult to contain.

Why has red rot become such a problem in India?

The answer may lie partly in the extraordinary success of a single sugarcane variety. Co 0238, also known as Karan 4, was released for commercial cultivation in 2009. It offered farmers high yields, better sugar content and early maturity. According to ICAR, it produced nearly 20 per cent more cane and almost 16 per cent more sugar than an older benchmark variety during trials.

Farmers embraced it. Co 0238 spread rapidly across Uttar Pradesh, Punjab, Haryana, Uttarakhand and Bihar. It helped lift cane yields and sugar recovery, particularly in northern India, and acquired the reputation of a “wonder cane”. But agricultural miracles carry a hidden risk when too many fields depend upon the same genetic material. A crop grown over a vast area as a monoculture gives a pathogen an enormous, continuous host population. Once the fungus adapts to that variety, it can travel quickly from field to field.

Co 0238 was originally described as moderately resistant to the red rot strains prevalent when it was released. Over time, however, newer strains of the pathogen appear to have eroded that protection. Uttar Pradesh has since introduced replacement varieties after red rot outbreaks damaged Co 0238 fields. The wonder cane helped create India’s sugar abundance. Its growing vulnerability is now exposing the danger of placing too much of that abundance in one stalk.

How does the disease spread?

Red rot can travel through infected planting material, soil, irrigation water, crop residue and rain splash. Sugarcane is not usually planted from seed. Farmers cut sections of mature stalk, called setts, and place them in the soil. If the parent cane carries the fungus, the next crop can begin life already infected. The pathogen may also survive in diseased stubble and crop debris. Waterlogging and poorly drained fields can encourage its spread, while injuries caused by pests or farm operations may give the fungus an entry point. This is why an infected field cannot be repaired simply by spraying whatever remains visible above the ground. Disease management must begin with clean planting material and extend across the crop cycle.

Can red rot be cured?

There is no simple field cure capable of reversing severe infection inside a cane stalk. The most effective defence is prevention: plant resistant varieties, use certified disease-free setts, remove infected clumps, destroy contaminated crop residue and avoid repeatedly planting the same vulnerable variety. Crop rotation can reduce the pathogen load in affected soil. Scientists also recommend treating planting material with hot water, fungicides or biological agents under prescribed conditions.

But the most important long-term response is varietal replacement. The ICAR study notes that resistant varieties remain the primary protection against serious losses, although resistance can break down as the fungus evolves. That means breeders must keep developing new varieties while farmers gradually retire those becoming susceptible. The fight against red rot is, therefore, an arms race. Scientists build resistance. The fungus searches for a way around it.

Is the sugar itself unsafe to eat?

Red rot is a crop-production disease, not an infection transmitted to consumers through refined sugar. The fungus damages the cane and degrades the juice before processing. Mills may reject badly affected cane because it yields less sugar and can interfere with processing. Refined sugar reaching the retail shelf does not “catch” red rot. For consumers, the immediate danger is economic rather than medical: lower cane yields, weaker sugar recovery and higher prices.

How sharply have sugar prices risen?

According to the Ministry of Consumer Affairs, the average retail price increased from ₹48.18 a kilogram on July 20 to ₹55.70 on August 20. That is a rise of roughly 15.6 per cent in one month. The timing magnifies the problem. Ganesh Chaturthi, Onam, Navratri, Dussehra and Diwali increase demand from households, sweet shops, food manufacturers and beverage companies. Even when a country possesses enough sugar on paper, tight stocks, uneven availability or fears about the next crop can push market prices higher.

The government now estimates production during the current sugar season at about 306 lakh tonnes, 11 per cent below the 343 lakh tonnes initially estimated by cane-producing states. India may technically retain a surplus after meeting annual consumption of around 280 lakh tonnes. But that cushion must also cover closing stocks, regional supply imbalances, festival demand and uncertainty surrounding the next harvest. A surplus can look comfortable in a ministerial statement and still feel thin in the market.

Why is El Niño being blamed?

El Niño begins with unusual warming in the central and eastern tropical Pacific Ocean. That warming alters air circulation and rainfall patterns across the world. For India and parts of Southeast Asia, a strong El Niño can weaken or distort monsoon rainfall. Sugarcane is a long-duration, water-intensive crop. Poor rainfall during planting and growth can reduce the number and size of stalks. Excessive heat can further stress the plant.

Weather damage and red rot can also reinforce each other. A crop already weakened by drought, heat, waterlogging or erratic rainfall may become more vulnerable to pests and disease. Reuters reported that the developing 2026-27 El Niño has more than a 90 per cent chance of becoming very strong. India and Thailand face the risk of drier conditions and lower cane yields, while excessive rain could interrupt harvesting in parts of Brazil. Red rot is the immediate biological enemy. El Niño is the larger climate threat hanging over the next crop.

Why is India importing sugar if it still has a surplus?

Because the government is trying to prevent tight supply from becoming a full-blown festival-season price shock. India has allowed one million tonnes of raw sugar to enter duty-free until October 31. The country normally levies a 100 per cent import duty, making overseas sugar commercially unattractive when domestic supplies are healthy. Removing that duty allows refiners and mills to buy raw sugar abroad, process it and release it into the Indian market. According to Reuters, port-based refineries may be able to supply around 300,000 tonnes from existing or rapidly accessible stocks. Larger shipments, expected mainly from Brazil, could arrive closer to October because of sailing and processing time. The decision is, therefore, as much about confidence as quantity. By signalling that more sugar is coming, the government hopes to curb hoarding, cool speculative buying and reassure bulk users.

Is India importing sugar for the first time?

No. Congress leader Randeep Singh Surjewala said India, which once exported sugar, was now importing it “for the first time”. That claim needs qualification. This is India’s first major sugar-import programme in nearly a decade, not its first import ever. India imported heavily after earlier production shortfalls. In 2009-10, for instance, imports of raw and white sugar totalled more than five million tonnes, according to Reuters’ contemporary reporting. What makes the present reversal striking is how quickly India has moved from being a major global exporter to seeking overseas supply again.

Did ethanol cause the shortage?

The government says no. Sugarcane can be used to produce sugar or diverted towards ethanol, which India blends with petrol. As the ethanol programme expands, critics argue that fuel production competes with food supply for the same crop. The Centre maintains that the amount of sugar diverted for ethanol has actually declined and that the present production revision stems mainly from crop damage and weather. Yet ethanol remains part of the broader structural equation. Mills must constantly decide how much cane juice or sugar feedstock goes into sweeteners and how much goes into fuel. In a bumper year, India can support both. In a disease-hit or drought-hit year, the margin narrows. Red rot may have lit the fire. The growing pull of ethanol determines how much spare sugar is available to extinguish it.

Is red rot only an Indian disease?

No. Red rot occurs across sugarcane-growing regions in Asia, Africa and the Americas. Its economic impact, however, differs from country to country because production systems and dominant crop varieties differ. India’s immediate vulnerability comes from the heavy concentration of susceptible varieties in important northern cane belts. Globally, weather may prove the larger market mover. Brazil dominates sugar exports and acts as the world market’s principal shock absorber. Thailand is another major exporter, while India can swing between exporting large surpluses and withdrawing from the international market to protect domestic consumers. When India imports rather than exports, the impact travels quickly. News of the one-million-tonne import quota pushed sugar futures in London and New York higher by about four per cent, Reuters reported. India is not merely buying from the global market. Its arrival as a buyer changes that market.

What does the global sugar picture look like?

The world is not running out of sugar, but the margin for error is narrowing. The US Department of Agriculture has projected global production at roughly 184.9 million tonnes in 2026-27, below the previous season’s record, while human consumption is expected to reach a new high. Brazil remains the pivotal supplier, but rain can disrupt its harvest and reduce the sugar content of cane. El Niño threatens dryness in India and Thailand. At the same time, biofuel policies in several countries allow mills to divert cane towards ethanol when that becomes more profitable. The global sugar market is consequently caught between three competing appetites: people want food, governments want cheaper fuel and markets want surplus stocks. Disease makes that contest sharper.

Will importing raw sugar bring prices down?

It should ease pressure, but not necessarily immediately. Some sugar can enter the domestic market relatively quickly through port-based refineries. Large Brazilian consignments may take weeks to arrive. The government has also imposed stockholding restrictions on bulk consumers to discourage hoarding and release supplies. Much will depend on whether traders believe the imports will arrive on time, whether mills release adequate stocks and whether the next cane crop shows signs of recovery. The Centre’s intervention can treat the price spike. It cannot cure the diseased fields that helped produce it. That is the harder lesson of red rot. India’s sugar security cannot rest indefinitely on one successful cane variety, one favourable monsoon or one emergency shipment from Brazil. It will require disease-resistant crops, cleaner planting material, greater genetic diversity and faster detection before the red streak inside a stalk becomes a red warning across the economy.

(With inputs from ANI)