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Stem rot of groundnut (Sclerotium rolfsii) Photo: Denis Ivanov · CC BY-NC 4.0 · source ↗

Stem rot of groundnut (Sclerotium rolfsii)

Stem rot, caused by the soilborne fungus Sclerotium rolfsii (perfect stage Athelia rolfsii), is one of the most economically damaging diseases of groundnut in Rayalaseema and the broader South Indian groundnut belt. ICAR-DGR (Junagadh) and ICRISAT (Patancheru) report yield losses of 10-25 percent in average years and up to 50 percent in heavily infested fields under continuous groundnut monocropping with high organic residue.

Identification and symptoms

The first sign is sudden wilting of individual plants or small patches in mid-canopy growth, typically 60-90 days after sowing. The collar region shows a white, cottony, fan-shaped fungal mat that climbs the lower stems and reaches the soil. Within 7-10 days, light brown to mustard-coloured sclerotia (1-2 mm spherical resting bodies) develop on the fungal mat and on infected plant debris. Affected plants are easily pulled up because the basal stems are macerated. Pegs and pods in contact with infested soil are also colonised, leading to pre-harvest pod loss.

Hosts and lifecycle

S. rolfsii has an exceptionally wide host range: groundnut, tomato, chilli, brinjal, lablab, onion, sugarcane, and most legume cover crops. Sclerotia survive in soil for 3-5 years and germinate on contact with fresh organic residue. Mycelium colonises plant debris first and then enters live tissue at the soil-stem interface. Optimum conditions are warm (25-35 deg C) moist soil with fresh undecomposed organic matter; outbreaks follow rain on freshly mulched or trash-incorporated fields.

Damage and economic impact

Yield loss occurs through direct plant death and through pod loss at harvest from buried pods that become detached. ICAR-DGR multi-location trials report 10-25 percent yield loss across South Indian groundnut belts in average years. Pod-stage infection raises aflatoxin (Aflatoxin Aspergillus Groundnut) contamination risk because the rotted pod tissue is colonised by Aspergillus flavus.

Management

  • Resistant varieties: ICGV 86590, ICGV 92093, TG 51 and CO-7 show field tolerance; popular varieties such as Kadiri-6 (Kadiri 6 Groundnut) and K-9 (K 9 Groundnut) are moderately susceptible.
  • Cultural: avoid groundnut after groundnut; rotate with pearl millet, sorghum or maize; deep summer ploughing exposes sclerotia to solar heat; remove and burn or fully compost the previous crop trash; raised-bed sowing (Raised Bed Groundnut) improves drainage and reduces collar wetness.
  • Soil amendments: neem cake at 250 kg/acre incorporated 2-3 weeks before sowing reduces sclerotium populations.
  • Bio-control: seed treatment with Trichoderma viride or T. harzianum at 4-10 g/kg seed combined with FYM enrichment; soil application of T. viride enriched FYM at 200 kg/acre.
  • Chemical: seed treatment with carboxin 37.5 percent + thiram 37.5 percent DS at 3 g/kg seed; in-furrow drench at the collar with tebuconazole 25 EC (1 ml/L), hexaconazole 5 EC (2 ml/L) or carbendazim 50 WP (1 g/L) at first symptom; combine with Trichoderma-enriched FYM for durable control.

See also: Aflatoxin in groundnut, Root-knot nematode in groundnut, Groundnut crop, Raised-bed groundnut, Early leaf spot.

Sources

  1. Stem rot of groundnut. ICAR-Directorate of Groundnut Research, Junagadh.
  2. Sclerotium rolfsii in groundnut. ICRISAT, Patancheru.