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

Anabe roga/Root rot

Causal organism: Ganoderma lucidum
Symptoms

Above ground

• Yellowing and browning of outer whorl of leaves. As the disease advances the inner whorl also exhibit the same symptom.
• Leaf dries at later stage of the disease, droops and hangs around the stem.
• The impact is the flowers, and nut size reduction and dropping.
• In severe or advanced stages, drooping of all the leaves and their dropping leaving only the stem with out leaves.
  
• Discolouration of vascular bundles can be seen.
On the trunk

• Stem bleeding and oozing of gum takes place upto the height of 5m as the disease advances.
• Below ground level - on roots
• The roots of the infected plant become brittle, discololured and dry.
• Sporophores and fruiting bodies can be seen on the stem portion at the collar region mostly after the death of the tree which gives the name “Anabe Roga (Mushroom like)”.
Etiology

• The fungus is heterothallic and weak parasite.
• Vegetative spores are the Chlamydospores.
• Conidia are round, thin walled. Sexual spores are basidiospores
Source of inoculum

• Primary source of inoculum:
• Chlamydospore and dormant mycelia survive in the soil and infected roots.
• Secondary source of innoculum
• Air borne basidiospores.
Mode of spread and survival

• It is a soil borne fungus and survives as dormant mycelium chlamydospores. Secondary spread takes place through the twisting of infected roots to healthy roots (through soil root).
• The mycelium present in the infected roots get transferred to healthy ones and thus spread the disease and spreads also through air.
Epidemiology

• Neglected plantations
• Sandy loam soils
• High plant population density
• Summer stressed plantations
life cycle

Management
Cultural control

• Fruiting bodies of the fungus, the dead stumps and roots of infected plants should be collected and burnt.
• Improving drainage facilities, avoiding dense plantation of palms and adoption of clean cultivation of gardens help in checking the disease.
• The fungus infects many plant trees, including avenue trees and such host trees should be avoided in the vicinity of the areca garden.
• The spread of the disease to neighboring trees can be prevented by digging deep trenches all round the affected palm and applying sulphur. Use drip irrigation during summer.
• Chemical control
• Soil drenching with calyxin solution (10ml/ lit) or stem injection.
• Biological control
• Application of Trichoderma viridae, (100 gram per plant) reduces the disease.