Diseases of fruit plantation medicinal and aromatic crops (2+1)

Bud rot

Causal organism: Phytophthora palmivora
It is one of the serious diseases of coconut and is fatal as the growing part of the plant is damaged. Bud rot incidence is high in palms growing in marshy, water-logging areas and in environments that promote high humidity (above 90%). The incidence is mostly found to be severe during, monsoon when RH is very high and temperature below 24°C. The pathogen remains dormant in the leaf base in dry weather and becomes active after getting the monsoon showers which indicates that unfavourable climatic conditions appear to be the primary cause of the disease and the fungal infection is considered to be secondary only.
Symptoms

• The first symptom is the discoloration of youngest leaf, withering of central spindle of the crown, rolling and death of growing point
• The tender leaf bases degenerate into a soil mass of purified material, emitting foul smell that attracts flies.
• When the base of the bud is badly affected, the palm finally succumbs.
• Bud rot is highly infectious and is spread by the wind during rainy season.


Etiology

• Mycelia:Aseptate, intracellular haustoria,
• Asexual spores: Zoospores,
• Sexual spores:Oospores
• Life cycle of phytophthora palmivora
• Primary source of inoculum – Dormant mycelia/oospores
• Secondary source of inoculum – Zoospores and sporangia
• Mode of infection-Through stomata
Epidemiology

• Cool weather
• Temperature- 180-200C.
• Relative humidity-100%
• Dense plant population,
• Time of South-West monsoon,
• Susceptible host.
Management
• In the bud-rot infected plantation, regular spraying with 1% Bordeaux mixture, just before and after monsoon to adjacent healthy palms is an effective preventive or prophylactic measure. Orchard sanitation through removal of dry material from the crown is also essential.
• If the disease is detected in early stage itself, application of Bordeaux paste on the crown, after thorough cleaning and removal of infected material, can check the disease.
• The treated portion should be given a protective covering with polythene sheet so as to prevent removal of the paste in the rains. It is best to remove infected trees and treat the surrounding palms.