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Late leaf spot of groundnut (Nothopassalora personata) Photo: wadia · CC BY-NC 4.0 · source ↗

Late leaf spot of groundnut (Nothopassalora personata)

Late leaf spot (LLS) is caused by Nothopassalora personata (formerly Cercosporidium personatum, Phaeoisariopsis personata; teleomorph Mycosphaerella berkeleyi). It is the second and economically more damaging half of the tikka complex, appearing 45-60 days after sowing and continuing through podding. LLS is consistently the highest-loss foliar disease of groundnut in India — 50 percent or more pod yield loss in unprotected susceptible crops, per ICAR-DGR and ICRISAT trials.

Identification

Lesions are 1.5-6 mm circular, dark brown to almost black, more prominent on the lower leaf surface where they bear dense black tufts of conidiophores (visible as a velvety sooty appearance under a hand lens). Unlike early leaf spot, LLS lesions typically lack a chlorotic halo, or have a very faint one. As the disease intensifies, leaves yellow and drop rapidly — heavy defoliation 60-80 DAS is the field signature of LLS.

Hosts and lifecycle

The pathogen is specific to groundnut and a few wild Arachis spp. It survives on infected residue and volunteer plants. Conidia disperse by wind, water and insects. Infection requires longer leaf wetness than ELS — 8-14 hours at 20-26 deg C is optimal. The latent period is 14-20 days, but spore production per lesion is much higher than ELS, so once LLS gets going the epidemic accelerates rapidly.

Damage and economic impact

LLS arrives during pod fill, so its impact on pod weight, kernel size and oil content is severe. Heavy defoliation also reduces haulm yield, an important secondary product for farmers who keep livestock. In Anantapur kharif groundnut, LLS combined with rust is the single largest source of preventable yield loss — well-timed fungicide programmes give 30-60 percent yield recovery.

Management

  • Resistant varieties: ICGV 86590, ICGV 87160, ICGV 91114, ICGS 76 and recent releases such as Girnar-4 and Kadiri-9 carry useful field resistance, much of it derived from Arachis cardenasii and A. duranensis via ICRISAT.
  • Cultural: remove crop residue and volunteer plants; rotate with cereals; avoid late kharif sowing in LLS-endemic tracts; intercrop with pearl millet at 6:1 ratio to slow spore spread (ICRISAT recommendation).
  • Chemical: ICAR-DGR's standard 3-spray schedule starting at 50 DAS controls LLS and rust together. Use mancozeb 75 WP at 2 g/L or chlorothalonil 75 WP at 2 g/L prophylactically; switch to systemic triazoles - tebuconazole 25 EC at 1 ml/L, propiconazole 25 EC at 1 ml/L, or hexaconazole 5 EC at 2 ml/L - once disease is visible. Tebuconazole + trifloxystrobin (Nativo 75 WG) at 0.4 g/L is the highest-yielding option in recent AICRP-Groundnut trials.

The economic threshold is the appearance of the first 2-3 lesions per plant on lower leaves — waiting longer typically costs more in lost yield than the saved spray.

See also: Tikka leaf spot in groundnut, Early leaf spot, Groundnut rust, Groundnut crop.

Sources

  1. Early and late leaf spots of groundnut. ICAR-Directorate of Groundnut Research, Junagadh.
  2. Nothopassalora personata factsheet. CABI Plantwise.
  3. Foliar fungal diseases of groundnut. ICRISAT, Patancheru.