Field Diagnostic Symptoms

• Brown spots with concentric rings in a bull's eye pattern with yellow margin.
• Fruit gets infected through calyx or stem attachment.
• Brown concentric rings on fruits.

Early symptom		Affected plant at advanced stage		Concentric ring on Fruits		Conidia

Causal organism

• Alternaria solani

Mycelium :

• coloured and septate

Pathogen :

• coloured, beaked conidia with transverse and longitudinal septae, borne singly or in chains

Survival and Mode of Spread

• Survival: Infected plant debris
• Primary spread: Infected seed
• Secondary spread: Conidia carried through rain, wind borne

Favourable conditions

• Warm, humid (24-29 degree C), rainy and wet weather.

Integrated Disease Management

• Removal and destruction of crop debris.
• Crop rotation.
• Seed treatment: Trichoderma asperellum @ 4g/kg seeds
• Spray Iprodione 50% WP @ 600 g/ac or Azoxystrobin 23% SC @ 200 ml/ac or Mancozeb 35% SC @ 1 kg/ac or Metiram 70% WG @ 1.0 kg/ac or Pyraclostrobin 20% WG @ 200 g/ac or Zineb 75% WP @ 800 g/ac or Azoxystrobin 18.2%+Difenoconazole 11.4% SC @ 200 ml/ac or Metiram55% + Pyraclostrobin5% WG @ 600 g/ac or Tebuconazole 50% + Trifloxystrobin 25% WG@ 140g/ac

Source of Information

• https:www.apsnet.org
• Crop production guide – Horticulture 2020.

Acknowledgement

• Photo courtesy by Dr.S.Vinodkumar
• Dr.P.Renukadevi, Professor, Department of Plant Pathology, TNAU, Coimbatore.