Diseases of Tea

Diseases of Tea

Blister blight – Exobasidium vexans

Symptoms

  • Small pale or pinkish circular spots appear on leaves and attain a size of 2.5 cm diameter.
  • The spots in the upper surface of the leaf becomes light brown in color and depressed while in under surface of leaf it bulges farming a blister like swelling.
  • Lower budget portion is covered with a white powdery growth of fungus.
  • When many spots coursers, curling of leaves will occur.
  • When it spreads to young succulent stems affected portion are withered.
  • The leaf yield is reduced vigor of the tea bush is affected.

http://agritech.tnau.ac.in/crop_protection/crop_prot_crop%20diseases_plantation_tea_clip_image002.gif

Pathogen

  • The mycelium is confined to the blistered areas on the leaves.
  • They are septae and collect in bundles below the lower epidermis.
  • Later by rupturing the epidermisa continuous layer of vertical hyphae are projected on the surface of spot.
  • The fungus produces two kind of spores viz.,the conidia and basidiospores.
  • The conidia are most abundant, borne singly at the tip of long stalks.
  • Basidia are formed on the surface in large number but never form a continuous hymenium.

Mode of spread and survival

  • The fungus completes its life cycle in 11-28 days and several generations of spores are produced in a season.
  • It produces conidia and basidiospores in the same blister.
  • Spores are air borne.
  • The perpetuation of the fungus appears to be form the pre existing infected bushes.

Management

  • Removal and destruction of the affected portion.
  • Spraying with Copper oxychloride 0.25 % in effective.
  • Spray with 210 g of COC + 210 g nickel chloride/ha at 5 days interval from June – September and 11 days interval in October – November gives economic control.
  • Spraying with systemic insecticides like Atemi 50 SL at 400 ml/ha (or) Baycor (300 EC) at 340 ml/ha a weekly interval is also effective.
  • Chlorotalonil, Bayleton, tridemorph is also effective.
  • Tridemorph at 340 and 60 ml/ha is satin factory under mild and moderate rainfall condition.

Black rot

Symptoms

  • Small dark brown irregular spots appear on leaf.
  • They coalesce to produce a dark brown patch which eventually covers the whole leaf and drop off.
  • Before the leaf turns black the lower surface assumes a white powdery appearance.

Pathogen

  • Corticium invisum and C. theae

Mode of spread and Survival

  • Basidiospores carried by workers.
  • The disease develops rapidly when temperature is high and air is humid.
  • At the beginning of rainfall they germinate and produce hyphae which start fresh infection.

Epidemiology

  • Occur in nursery shaded with Crotalaria.
  • Basidiospores germinate only in wet weather or when leaves are covered with dew.

Management

  • Prune in December end, remove the prunings immediately, burn after drying.
  • Collect all dead and dried leaves.
  • Spray a copper fungide in third week of April.

Red rust: Cephaleurus mycoidea

Symptoms

  • Orange yellow, circular patches appear on upper surface of leaves.
  • The spots become brown and dry up.
  • When it affects the given stem it hardens prematurely.

http://agritech.tnau.ac.in/crop_protection/crop_prot_crop%20diseases_plantation_tea_clip_image004.jpg

Pathogen

  • Cephaleurus mycoidea also attacks Tephrosia sp. and Desmodium gyroides grown as green manure and shade.

Epidemiology

  • Rainy season is best suited for propagation of algae.

Management

  • Removal of infected portion and spraying with Copper oxychloride 0.25 %

Black root: Rosellina areuata

Symptoms

  • The fungus originate from the dead heaped leaves of 5 – 7.5 above the soil level.
  • From there if spreads to roots region of tea bushes.
  • When bark is removed star like growth of mycelium can be seen.
  • At the surface of the soil the mycelium surrounds the stem and kills the bank for the length of 7.5 – 10.0 cm.
  • A swollen ring of tissue is formed round the stem above the dead patch.

Pathogen

  • The fungus produces two kinds of fructification, a conidial stage and a perithecial stage.
  • The conidia are borne on short bristle like stalks.
  • The perithecia are black and spherical.
  • They bear asci which in turn bear ascospores.

Mode of spread

  • The disease is spread by wind

Management:

  • Removal and destruction of infected plant.
  • Clean cultivation with out fallen leaves.
  • Dig a drench around the infected bush to provide sunlight in the drench which prevent the spread of mycelium.

 

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