Submitted by Spicepedia
This disease is severe in many vanilla plantations, especially during rainy season. Two kinds of rot caused by two different species of fungi are recorded.
In India and Indonesia, the occurrence of this disease on vanilla is heavier during the rainy season. The causal organism is Phytophthora meadii in India.
The fungus is air borne. Excess shade in the plantations, continuous rains, crowding of vines, water logged conditions, heavy rainfall, high relative humidity (>90%), low temperature of 22-25°C and less sunshine hours favour the disease.
Phytophthora rot develops from the tip of the bean, forming water soaked lesion, which slowly extends towards the pedicel becoming darker green. The eventual necrosis extends to the whole bunch of beans, sometimes exhibiting abundant external growth of mycelium. In advanced stages of infection the rotting advances to the stem, leaves, aerial roots and extends to the entire vine. Eventually the whole vine decays and the entire plant perish.
Phytophthora bean rot
Sclerotium rot of vanilla
The disease is reported in India and Indonesia.
Presence of white mycelium around the infested plant parts and light brown sclerotia on basal stems and surrounding soil surface are characteristic diagnostic symptoms. The rotting initiates from the bean tips and advance towards the stalk regions. The infected beans show rotting symptoms with deep sunken wound like areas, which appears reddish brown in colour. Running threads of fungal mat is seen on the leaves and beans and rarely on stem also.
Excess shade, continuous heavy rains, overcrowding of vines, waterlogged conditions and the presence of pathogen inoculums in the field are predisposing factors of bean rot. Dormant structures called sclerotia can persist in the soil for years. These structures are easily spread by rain water splash and run off. Under favorable environmental conditions, the sclerotia germinate and form mycelia mats, which colonize the host tissue.
Remove and destroy infected plant parts and mulch during rainy season. Regulate shade during monsoon period in order to prevent excess shade. Allow at least 30-50% light to fall on the vines. Spray Bordeaux mixture (1%) and drench soil with 0.25% copper oxychloride 2-3 times depending on the severity of infection and as a prophylactic measure. If rotting is due to Sclerotium, carbendazim-mancozeb mixture 0.25% can be sprayed twice at 15 days interval.
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