Diseases of Fruit Plantation Medicinal and Aromatic Crops

Nursery disease

Coffee is mainly propagated through seeds. Seedlings are raised in two stages under pandel shades.

The seedlings in the nursery are infected by the following diseases.

Collar rot
Causal organism: Rhizoctonia solani Kuhn.
Classification
Class- Deuteromycotina,

Order- Myceliasterilia.

Collar rot or Damping off disease occurs on seedlings of 1-3 months age in the nursery if the conditions are favourable for growth of the fungus. Seedling loss may go up to 10-20% depending upon the severity of the infection. Both the commercially important cultivars of coffee are susceptible to this pathogen. The causal agent of collar rot fungus is reported to be soil inhabitant & is prevalent in all the coffee growing areas of India.
Symptoms

• The pathogen attacks seeds & seedlings both in the following two stages.
• Pre-emergence damping off: Embryo & endosperm are invaded by the fungus before germination and the radical during germination resulting in seeds rot and disintegration.
• Post-emergence damping off: Seedlings show brownish discoloration on the stem near the ground level leading to rotting of the tissue. Growing apex wilts, the seedlings collapse and die.
Favourable factors

• Impeded drainage in the nursery beds resulting in excessive soil moisture, thick covering, hot and humid weather, over crowding of seedlings etc create unfavourable environment for seedling growth & pre-dispose them for infection by the fungus.
• Expose nursery soil to the sun for 2-3 months.
• Prepare raised seed beds adding forest soil, compost & sand to drain off the excess moisture in the bed.
• Avoid excessive watering.
• Avoid over-crowding of seedlings through proper spacing of seeds while sowing.
• Provide filtered overhead shade using coir mats.
• Treat coffee seeds with carbendazim @ 2 g per kg before sowing