Red Rust of Tea

Causal organism:

1. Cephaleuros parasiticus Karst

2. Cephaleuros mycoidea Karst

Type of organism: Algae.

Introduction:

This is an algal disease, common on tea and many other plants including coffee, guava, citrus and other cultivated and jungle tree. Usually this is epiphytic on the leaves and may also become parasitic. This disease is found in most tea garden in the country. This disease spread rapidly during humid weather accompanied by bright sun.

Key words: algal disease, epiphytic, parasitic, humid weather, bright sun.

Symptom:

1. The algal appears as minute rusty spots on the leaves.

Fig: A leaf of tea showing minute rusty spots on it

2. Spots enlarge, become roundish and increasing to about 10-15 mm in diameter.

3. Spots are reddish and hairy occurring on the upper leaf surface.

4. Damage is caused by reducing the effective area of photosynthesis.

Fig: Leaf of tea showing severely infected red rust symptom

5. Algae enter leaf through epidermis and take nutrient as parasite, and then the plants are severely affected.

6. Severely infected leaves are discolored.

7. Spots spread to stem.

8. Infected stems become pale and appear unhealthy even from a distance.

Disease cycle:

The disease is more or less chronic. Algae can survive in the stem and old leaves all the year round. Become severe when bright sunlight is available and also when new flush comes out. The secondary spread is through wind-borne inoculums.

Key words: stem and old leaves, bright sunlight, new flush, wind borne.

Mode of infection:

The algae forming sporangia on infected leaves and stem, which are exposed to the air. The algal cells are impregnated with a red pigment, which mask the green chlorophyll, and hence the red color.

Orange colored zoospores are formed inside the sporangia. They are round to ovoid and biflagellate for swimming in water. They germinate to form the characteristic thallus.

Key words: sporangia, red pigment, masking chlorophyll, red color, orange zoospore, round to ovoid, biflagellate, thallus.

Control measure:

It is very difficult to eradicate the disease after establishment. Regulating the overhead shed and pruning and plucking of infested leaves and shoots may help in reducing the damage caused by this alga.

Key words: overhead shed, pruning and plucking.