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

Fusarium bark disease

Causal organism: Fusarium stilboides (syn. Gibberala stilboides)
It is important in South East Asia, Southern Africa & West Indies.
Symptoms

• The pathogen infects the collar region of the stem and produce bark canker. Bark scaling is the most common but least damaging symptom.
• The fungus grows beneath the bark layer that becomes flaxy in texture.
• Cankers are then produced which can girdle the trunk and kill the tree.
• Damage is also caused due to young suckers, where a necrotic brown lesion develops at the base, usually close to the junction with the main stem.
• The sucker may get killed or survive to have a constricted ‘bottle neck’ appearance at the base, which leaves the new stem weakened & liable to break when heavy crop is borne.
Epidemiology

• Insect damage may initiate attacks. Unfavourable conditions like poor soil management, irregular pruning & drought predispose the plant to infection.
• Mode of spread & survival
• The pathogen is a common inhabitant of coffee stem surfaces & survives saprophytic ally on dead coffee debris.
• It may also infect damaged coffee berries as a secondary invader.
• The pathogenic phase only occurs when the coffee plant is stressed by wounding or under favourable climatic conditions.
Management

• Good soil management with adequate & timely mulching to conserve moisture in the top layers of the soil, proper pruning practices, improving to soil fertility, etc. reduce the infection.
• The protection of stem bases with Captan or captafol (0.4%) sprays on the trunk bases after pruning and when young suckers are maturing, also recommended.
• Pruning cuts or other wounds should be protected with a fungicidal paint. Badly diseased trees should be destroyed.