It is a wound parasite prevalent in all tea areas. The fungus (Poria hyppbrunnea Petch) gains entry through the unprotected wounds especially on thicker branches, caused by various agencies such as heavy pruning cuts, sun scorched lesions, damages with ragged surfaces made by careless chopping or cutting off branches or falling of shade trees, wounds made by hail, cattle etc.
On weak bushes, even wounds on smaller branches may be affected by the disease. From the first site of infestation through stem the fungus gradually moves downwards killing the entire plant. It may take 8-15 years to kill a mature bush and 2-3 years a young plant.
The infested wood turns yellowish, soft and decays. Thin, irregular, light brown lines are formed in the wood which are permeated with thin sheet of yellowish-brown mycelium. It produces yellowish (later dark grey) corky fructification on the underside of big branches at their base or collar region. Infection spreads through air borne spores.
Thorny Stem Blight
This disease is common in Darjeeling and Dooars in NE India, in the up country of Sri Lanka and in Malawi. The causal organism of this disease is Tunstallia aculeata (Petch) Agnihothrudu.The disease is also known as Aglaspora in Darjeeling. The pathogen enters the stem through pruning cuts and wounds, then spread downwards killing the branches until it reaches the collar and finally the roots, when the plant is killed.The disease is only recognised by fructifications which are small, black, raised, throne like projections and are produced on dead branches. It is a disease of weak bushes.
Collar canker caused by the fungus Phomopsis theae Petch is an important disease in South India. It is also ocuur in the higher elevation of Sri Lanka and Africa.The disease is generally found to occur in young clobal and replanted areas between two to eight years. Cankers are produced at the collar and on branches. An injury on the collar offers ready avenue of entrance of the fungus. Chlorosis, ceasation of growth and profuse flowering are the common symptoms of the disease.
Wood rot caused by Hypoxylon serpens (Pers.ex Fr.) kick is an important stem disease in Sri Lanka, Malyasia, Kenya, Malawi, Zimbabwe and Tanzania and also in South India. The fungus enters the stem through moribund tisse following injury by sun scorch. Once the fungus gains entry into the stem it spreads gradually within the branches, ultimately reaching the stem. Often only one branch or a portion of the bush which is affected by “wood rot” dies, but when the infection girdles the main stem the entire bush is killed. Irregular, slightly raised, whitish-grey to dark patches form on the affected wood.
Pink disease caused by Corticium salmonicola Berk & Br. Has been reported from India, Sri Lanka, Indonesia and Southern China. It also occasionally affects branches of tea in the wetter parts of Kenya, Burundi, Cameroon and Madagaskar.The bark of the affected branch cracks and a pink encrustation travels down the branch on lower side. The affected branches loses leaves and dies-back.
Nectria is a wound parasite, several species of which occur on tea in N.E. India. Only two of the species have so far been found to be harmful to tea. In N.E. India, Nectria cinnabarina Fr. causes die-back of tea stem. It attacks mature tea bushes. Affected branches die-back from the site of infection. The weak bushes suffer the most. The fungi spread by air-borne spores.