Diseases of Fruit Plantation Medicinal and Aromatic Crops

Bud rot

Causal organism: Phytophthora palmivora
Symptoms

• The fungus Phytophthora palmivora. P meadii causing koleroga in bunches also pass on to the buds and cause rotting.
• The first symptom of the disease is the discoloration of the spindle from the natural light green color to yellow and then brown.
• Infection spreads to young leaves which rot rapidly. As the infection spreads inside the bud the growing point of the stem also rots resulting in the death of the palm.
• The spindle slumps and can be drawn out with a gentle pull.
• The outer leaves then become yellow, droop and drop off one by one leaving a bare stem. Secondary organisms colonize the rotting bud and convert it into a slimy mass which would emit a foetid smell.
Etiology

• The mycelia are aseptate with intercellular mycelium and the haustoria.
• Zoospores are the asexual spores borne in sporangia.
• Oospores are the sexual spores borne in oogonium.
• Primary source of inoculum: oospores.
• Secondary source of inoculum: zoospores.
Epidemiology

• This organism require cool weather condition, temperature requirement is 18-20? c, relative humidity is 98-100%, require cloudy weather, intermittent rainfall & high density plantation. It occurs in sever form in heavy rainfall tracts of Karnataka.
• It generally occurs in monsoon season.
• Fresh infection during November onwards becomes severe during succeeding months.
Management

• Infected tissues of bud are to be scooped off and treated with Bordeaux paste.
• Destruction and removal of dead palms and also the branches affected by mahali and drenching the crowns of surrounding healthy palms with Bordeaux mixture (1%) help in reducing the disease incidence.
• Soil application of Trichoderma reduces the inoculum in soil.