Sugarcane Red Rot in UP: Co-0238 and Replacement Varieties

Overview

Uttar Pradesh is undergoing a massive agricultural transition. The high-yielding sugarcane variety Co-0238 (Karan 4) has suffered widespread resistance breakdown against red rot disease, caused by the fungal pathogen Colletotrichum falcatum.

To safeguard farm incomes and factory recovery rates, the state replaced over 12.38 lakh hectares of susceptible cane between 2021 and 2025. This effort rebuilds varietal biodiversity across subtropical growing zones.

Intensive monoculture previously expanded Co-0238 to cover over 80% of Uttar Pradesh's cane area. That concentration accelerated pathogen virulence through the vertifolia effect. Shifting to resilient alternatives like Co-0118 and Co-20016 proves that long-term agro-economic security demands genetic diversity over perpetual reliance on a single super-variety.

The Uttar Pradesh Sugarcane Development Department has accelerated the phase-out of landmark cane variety Co-0238 following destructive red rot outbreaks across major growing belts. The disease took a severe toll on production.

As of September 2026, state sugar production fell from 126.4 lakh tonnes in 2019–20 to 89.5 lakh tonnes in the 2025–26 season, primarily driven by red rot damage and varietal failure.

Widespread field losses across western and central mill command zones forced the rollout of emergency seed multiplication programmes and resistant cultivars. This crisis highlights how genetic monoculture can turn a thriving cash-crop belt into a vulnerable production landscape.

Red rot disease is an internal vascular infection caused by the hemibiotrophic fungal pathogen Colletotrichum falcatum Went. Farmers and scientists frequently call it the cancer of sugarcane. The teleomorph stage of the fungus is classified as Glomerella tucumanensis.

Primary infection starts via pathogen-carrying seed setts or fungal inoculum surviving in buried crop residues. Secondary transmission spreads quickly through irrigation flows, floodwaters, and airborne conidia that enter nodal tissues of standing stalks.

Diagnostic symptoms of red rot develop inside the cane stalk:

• Internal reddening across vascular bundles and ground tissue.
• White horizontal crossbands running perpendicular to the stalk axis.
• An alcoholic fermentation odour caused by rapid fungal conversion of sucrose into reducing sugars.
• Complete wilting of crown leaves, terminating in dry-rot hollow cavities inside affected internodes.

Dr. Bakshi Ram bred the miracle sugarcane cultivar Co-0238 (Karan 4) at the ICAR-Sugarcane Breeding Institute Regional Centre in Karnal before its formal release in 2009 for the Northwest Zone. The variety delivered high tillering, thicker stalks, early maturity, and superior sucrose concentration.

Growers across Uttar Pradesh saw an immediate boost in field output. Average agricultural productivity jumped from under 60 tonnes per hectare to more than 80 tonnes per hectare.

Sugar mills also recorded rapid gains in processing efficiency:

• Mill sugar recovery rates rose from around 9% in 2010–11 to over 11.5% by 2019–20.
• Higher recoveries generated stronger cash flows for mills, speeding up the clearance of cane price arrears to farmers.
• Elevated per-acre returns triggered rapid adoption across subtropical North India.

The ICAR-Sugarcane Breeding Institute documented that Co-0238 expanded to occupy 82% to 88% of the total sugarcane area in Uttar Pradesh by 2019–20. This extreme geographic concentration created a continuous genetic monoculture across millions of contiguous hectares.

Epidemiological vulnerability worsened because of continuous ratoon cropping and widespread trading of uncertified planting setts. Unbroken cultivation of a single cultivar created strong selection pressure on field pathogens. This triggered the vertifolia effect — a swift breakdown of horizontal resistance as specialized fungal mutants proliferate.

Resistance collapsed completely once a virulent new pathotype, CF13, emerged and multiplied across subtropical belts. The CF13 pathotype easily bypassed the internal defences of Co-0238, turning a former super-variety into a vulnerable host.

The Ministry of Agriculture and Farmers Welfare collaborated with state research stations to evaluate resilient replacement cultivars against Co-0238. Moving to newer genotypes provides protection against the CF13 pathotype while maintaining field tonnage and juice recovery levels.

State agricultural authorities have also notified other promising alternatives, including CoLk-14201 (Ikshu-6), CoLk-16202, CoS-13235, CoS-17231, and CoSha-19231. Planting a balanced mosaic of these varieties stops pathogens from adapting to any single genetic line.

The Cane Commissioner Office in Uttar Pradesh noted severe economic fallout across the rural economy as red rot tore through Co-0238 fields. Standing crop destruction forced early harvesting, reduced total tonnage, and cut into farm income.

Sugar mills suffered direct processing losses as fungal sucrose inversion damaged cane juice quality:

• Fungal enzymes inverted sucrose into non-crystallisable glucose and fructose, slashing recovery rates.
• Lower recoveries drove up industrial crushing costs per quintal of sugar.
• Total state sugar output contracted by 36.9 lakh tonnes between 2019–20 and 2025–26.

Factory zones responded by placing limits on varietal concentration. Cane experts recommend that no single cultivar should exceed **** of total acreage in any mill command area to maintain genetic resilience.

The ICAR-Indian Institute of Sugarcane Research (IISR) in Lucknow is rolling out decentralised seed production techniques to replace infected planting stock. Replacing seed volume across millions of hectares requires high multiplication ratios.

Modern seed multiplication methods include:

• Single-bud sett planting and bud chip settling nurseries using portray technology to minimise basic seed requirements.
• Tissue culture micropropagation to distribute certified disease-free foundation stock to registered seed producers.
• Moist Hot Air Treatment (MHAT) of foundation setts at 54°C for 2.5 to 4 hours to kill latent internal mycelium.

Farmers encounter real logistical hurdles during varietal replacement. Infected ratoon crops carry lingering pathogen reservoirs, forcing growers to uproot and burn stubble rather than continuing traditional multi-year ratooning. Growers must also adjust to differing tillering patterns and irrigation needs of replacement varieties.

The Department of Agriculture & Farmers Welfare promotes an integrated pest and disease management strategy combining chemical treatments, biological control, and cultural field practices. Long-term disease control requires moving past routine chemical sprays toward soil health regeneration.

Key strategies for building sugarcane resilience include:

• Chemical Sett Treatment: Dipping seed setts and drenching planting furrows with systemic fungicides like carbendazim, thiophanate-methyl, or hexaconazole before planting.
• Biological Inoculation: Applying bio-formulations of Trichoderma viride and Trichoderma harzianum at planting to suppress Colletotrichum falcatum inoculum in the rhizosphere.
• Agronomic Sanitation: Enforcing crop rotation with non-host crops like paddy or green manures such as Sesbania (dhaincha).
• Drainage Management: Using laser land levelling to eliminate waterlogging that accelerates secondary fungal spore dispersal.
• Institutional Varietal Ceilings: Mandating strict varietal zoning policies to ensure no single cultivar crosses safe saturation thresholds.

• Pathogen Biology: Sugarcane red rot is caused by the hemibiotrophic fungus Colletotrichum falcatum Went, leading to internal vascular reddening, white crossbands, and sucrose inversion.
• Economic Legacy of Co-0238: Bred by Dr. Bakshi Ram, Co-0238 elevated Uttar Pradesh sugarcane yields past 80 t/ha and sugar recovery past 11.5% before succumbing to the virulent CF13 pathotype.
• Monoculture Breakdown: Saturation of Co-0238 across 82–88% of UP cane area induced a severe vertifolia effect, causing state sugar output to decline from 126.4 lakh tonnes in 2019–20 to 89.5 lakh tonnes in 2025–26.
• Varietal Transition: UP replaced 12.38 lakh hectares of Co-0238 between 2021 and 2025, expanding resilient cultivars like Co-0118 (26.02% area in 2025–26) and advancing promising varieties like Co-20016.
• Integrated Management: Disease management requires seed sanitisation via Moist Hot Air Treatment (MHAT), Trichoderma bio-control, termination of infected ratoons, and enforcing a 40–50% varietal ceiling per factory zone.