Diseases of Fruit Plantation Medicinal and Aromatic Crops

Red rust disease

Causal organism: Cephaleuros mycoidea Karst

The trivival name of this disease is a misnomer.
The cell contents of the genus, Cephaleuros are orange red, hence the misapplication of the name rust.
The disease is widespread and important in India, Sri Lanka, Africa and America.
It attacks all kinds of tea plants both young and old when vitality is impaired.
It is occurring on tea plants in many parts of India.

Symptoms

• On leaves the alga may sometimes exist as parasite or sometimes as epiphytes while in the stem it is normally in parasitic form producing cankers and killing the tissues.
• The leaf infection can be seen throughout the year in an acute condition while the stem infection may escape at certain periods.
• The leaf infection of red rust does little damage, but it is important in that it serves as a source of stem infection.
• The alga occur as orange yellow, roughly ciruclar patches on the upper surface of the leaf. The patches may be few or numerous, crowded or scattered and may occupy any part of the leaf. They are rare on the petiole.
• Under favourable conditions the algae penetrates the leaf tissues
• The penetrating filaments may extend laterally between epidermis and adjacent layers and also downwards between palisade cells.
• The filaments never penetrate leaf cells but get nourishment through osmosis.
• The host cell that comes in contact get killed and their contents turn brown and become dry. Ultimately the alga itself ceases to grow, cells die and a crater-like depression is left surrounded by an elevated ring.
• On stem, the pathogen occurs as red hairy patches
• The new shoots arising from infected wood show lack of vigour or even cease to grow prematurely.
• As a result of infection, the host bark is removed in successive layers and where this fails, the parasite penetrates deeper, into the cortex and may ultimately cause death of the shoot.
Causal agent

• Cephaleuros mycoidea Karst. Red rust also attacks Tephrosia sp. and Desmodium gyroides grown as green manure and shading plant
Epidemiology

• Rainy season is best suited for propagation of alga.
Management

• The algal parasite may be tackled in two ways:
• Removal of all infected portions by Bordeaux mixture spray.
• The other approach is by increasing the vigour of the bushes, since it is considered that there is a direct correlation between lack of vitality of the bush and the virulence of the disease.
• Improving the nutrient status of the soil through application of nitrogen, phosphorus and potassium fertilizers is important.
• Destruction of infected plant parts should be done.