Early leaf spot:  Cercospora arachidicola(Mycosphaerella arachidis)

Symptoms:

• Infection starts about a month after sowing
• Brown circular lesion with yellow halo on leaves
• Light brown colour appears on lower surface of leaves
• Lesions appear on petioles, stems and stipules

Early leaf spot

Pathogen:

• Intercellular mycelium: Olivaceous brown
• Conidiophores:  Short, 1 or 2 septate, unbranched and geniculate
• Conidia: Sub hyaline, 3-12 septate with round base and sub-acute tip
• Asci: Cylindrical to clavate and contain 8 ascospores
• Ascospores: Hyaline, slightly curved and two celled

Conidia

Favourable Conditions:

• Prolonged high relative humidity for 3 days
• Low temperature (20ºC) with dew on the leaf surface
• Heavy doses of nitrogen and phosphorus fertilizers
• Deficiency of magnesium in the soil

Mode of Spread and Survival:

• Pathogen persists as inactive mycelium and perithecia in soil
• Primary spread: Ascospores
• Secondary spread: Airborne conidia

Management:

• Seed treatment with carbendazim @ 2 g/kg of seeds or mancozeb 75% WP @ 3 g/kg of seeds
• Spray carbendazim @ 500 g/ha or mancozeb @ 1000 g/ha or chlorothalonil @ 1000 g/ha. If necessary, repeat the spray after 15 days