Shahjalal University of Science & Technology

SYLHET

Assignment on Disease Scenery of BD. In Tea

Md. Saidur Rahman KhanReg. No. 2006337004

Semester 3/1Dept. of Food & Tea Technology

SUST

IntroductionTea disease can be defined as the malfunctioning of host cells, & tissues those results from pathogenic agents or environmental factors & lead to the development of specific sympoms.

Tea disease and tea productivity are two antagonistic factors. Disease management for tea is a long term process and its success is dependent upon the selection, integration and continued consolidation of both adaptive and technological strategies of disease control.

About 380 fungal & 1 algal diseases are observed in tea world. In our country, 22 diseases are found in tea area where 18 are fungal, 3 bacterial & 1 algal diseases are found.

About 10-15% of yield is reduced in our country by fungal diseases.

Classification of Tea DiseaseAccording to the causes of origin Tea Diseases

Disease caused by living organism/ Disease caused by non-living organism biotic agents abiotic agent

Fungal Disease Bacterial Disease Algal Disease Viral Disease

Nutritional Deficiency Adverse environmental condition

Climatic Poor soil & water Acid soil & lack Defective cultural Condition logging of soil nitrogen practices

Pathogenic Process of Tea DiseasePathogens may invade plants by means of toxin or enzyme secretion & cause the destruction of cell & cytoplasmic membrane, inhibition of growth or death of plants.

The process of pathological infection is operated by two phases:1. Pathogenesis

It means the disease producing phase which occurs during the cropping season.

2. SaprogenesisIt means the dormant phase which occurs during the cold or dry season.The pathogenesis phases have three distinct successive stages. These are:

Inoculation StageSpores, mycelium etc. of pathogens, termed as inocula, initiate the diseases.This stage begins at the moment the inocula are driven or carried away by wind, rain, dew, pluckers etc. from the source of infection & ends when it lands on or in the infection sites.

Incubation StageDuring this stage, the germination & development of spores, the entrance & multiplication of the pathogen are performed in host tissues.It begins at the moment when the inocula land on the infection site & ends with the beginning of pathogenic reactions of the plant.

Infection StageThis stage includes the period when the pathogen is irritating the plant & producing characteristics symptoms. This stage may last from a few days to several years, depending upon the nature of the pathogen, age & type of host plants, temperature, moisture & other factors.

Symptomatic Key to diseasesThe following key is prepared to enable the planters to identify the most common diseases of tea plants:

A. Foliar Diseases:1. Greyish white to black, brownish yellow chocolate coloured patches in mature

maintenance leaves; infected dried leaves attached to other leaves & / or stems by a thin creay threads

2. Powdery white or pinkish, concave blisters on flush & under surface of leaves.3. In nursery, leaves gryish, irregular concentric rings of dark spots, leaf fall. 4. In nursery & young plantation, leaves with yellowish brown patches on upper surface;

concentric rings-Brown rings within one another, leaves often dried & shed. 5. In nursery & young plantation, shoots die-back;yellow to brown lesions girdling

apical stem, petiole, bud; leaves wilted & withered.

B. Stem Disease:1. Chalky white thread or strands on stem or branch, fan-like spread of threads under

surface of leaves.2. Tufts of black hair-like strands entangling foliage, stems, branches of bush. 3. Ring of callus surrounding sunken lesion of stump; branch often split; bark peeled off.4. Young branch with black lesions on bark; ring barked by callus growth; leaves wilted,

dried up; die-back of lateral branches.5. Leaves variegated with yellow patches, brick red, orange coloured spots on

stem;twigs died, leaf fall.

Some Major Tea Diseases Occurred in the Tea Garden:

1. Foliar Diseases Black Rot. Blister Blight. Grey Blight. Brown Blight. Die Back.

2. Stem Diseases Horse Hair Blight. Branch & Stump Canker. Collar Canker. Red Rust / White Blight.

3. Root Diseases Charcoal Stump Rot. Violet Root.

These diseases are briefly discussed below:

Black Rot:

General Description1. The disease Black Rot is a kind of foliar disease caused by Corticium invisum Petch

& Corticium theae Bern is responsible for this disease.2. It is generally found in India, Sri-lanka & Bangladesh.3. It is a common disease in plain region but rare in hilly area.4. It severe cases, 15% reduction of shoot growth occurred.5. It generally attacked on May, June, July & September & then over winter.

Symptoms1. Large brown patches on leaves resembling sun scorches.2. Small grayish brown dots under the margin.3. Black shiny spots on young leaves during wet weather.4. During severe infection, infected leaves are drops down.5. More prevalent on tea which has been cut across without cleaning.

Life cycle1. The fungus invades leaf tissues by a thin web of white hair like mycelium.2. The spores, basidia are club shaped each with four spores at the end of four horn-like projections, sterigmata.3. Spores are wind borne & spread rapidly from bush to bush through air currents, leaf filtering, Laborers clothing etc.4. During the onset of cold weather, September-October, the fungus dries up & form minute resting organ, sclerotia.5. At the onset of the rainy season, March-April, the sclerotia swell up & fructification starts through the production of mycelial strand or hyphae, about 0.5 mm in diameter.6. Hyphae are then transformed into absorbing organ, haustoria which invades plant tissues.

Fig. : Life cycle of Black rot disease of tea plant, Corticium invisum Petch

Control Measures

Cultural Control Pruning & Skiffing on severe affected section. Improve the aeration. Thinning out the dense shade. Improve drainage system. Alkaline wash after pruning. Adoption of shorter pruning cycle.

Chemical Control Blanket spray of cufungicides between 15 days interval twice in mid April-mid May. Use systemic fungicide like vitavex 75 WP or delan 75 WP to suppress sclerotia.

Blister Blight:

General Description1. Tea Blister Blight is a kind of foliar disease caused by Exobasidium vexans Massee.2. It is a dreadful fungal disease.3. It is prevalent in India, Japan, Indochina, Formosa, Java, Sumatra, Indonesia,

Sri Lanka & most of tea growing areas in tropical & sub-tropical zone.4. Crop losses upto 30% are reported from the attack of this disease. 5. In Bangladesh, a few sporadic incidences had been observed in 1964 in several tea

gardens viz. Pallathal, Phulbari & Deanston tea estates.6. During the last three decades the disease has been found localised in many gardens

having two epidemics during 1965-80.

Symptoms1. Only young tea leaves & stems are infected.2. At first the symptoms is visible to the naked eye as a pale yellow, translucent oval or

circular spot, about 12.7 mm (about a half inch) in diameter on the undersurface of young, succulent leaves.

3. Corresponding spots on the undersurface are concave, yellowish & glistening with upper surface convex.

4. On maturity, the blisters coalesce, enlarge as irregular circles, about 12 mm in diameter.

5. Later the blisters turn brown to black.6. As the fungus continues to grow inside the leaf, the upper surface of the developing

blisters becomes indented, corresponding with a protrusion of the lower surface.

Life Cycle1. The pinciple disease-carrying propagules are the basidiospores which are produced in

enormous nubers from each blister.2. Basidiospores are producedon the basidia.3. Each basidium is provided with two projections or sterigmata & lies between

numerous paraphyses.4. Paraphyses are simple, septate, round at the apex while the basidiospores are

ellipsoid, hyaline, aseptate in the early stage but later have central septum, measuring 13-27×4.3-6.5µ.

5. Spores are wind borne & short lived.6. When a spore falls onto the surface of a young leaf which is wet with dew or rain, it

germinates through the epidermis into leaf tissues.7. After an incubation period of 5-8 days, the infected leaf develops a round, translucent,

creamy yellow spot, called Oil spot at the point where the spores entered.8. These spots are glistening, concave on the upper surace & whitish, convex on the

undersurface.9. The sporulation commences on or about the eighth day & lasts a week.10. During sporulation the blister appeare white & powdery.11. The cycle of sporulation is completed within 8 & 21 days from the time of

sporulation.

Fig. : Life cycle of Blister Blight of Tea, Exobasidium vexans Massee.

Control MeasuresCultural Control

1. Regular monitoring specially in Kunchi areas & heavily shaded sections is essential.2. Thinning out the shade canopy, if necessary, in kunchi areas.3. Clearing the adjacent jungles to permeate sunshine & air-circulation is important.4. Tea in plucking, if infected in isolated sections, should be plucked hard & the

infected leaves should be burnt.5. Pluckers should not be allowed to move from infected sections to new areas.6. Plucking baskets that held infected shoots should not be used unless washed off or

sun-dried.7. Green crops in young tea should be kept well-hedged & lopped periodically.

Chemical Control:1. Eradication of source of infection in abandoned tea nurseries, diseased seedbaries &

young tea by a prophylactic spraying with any copper fungicide during January-March as per spraying schedule.

2. Tea in plucking must receive the first prophylactic cum palliative spraying during September-October with approved fungicides.

Grey Blight:

General Description:1. This disease is a kind of foliar disease caused by Pestalozia theae Sawada.2. This is the ommon oliar disease of tea in Bangladesh, India, Sri Lanka & Africa.3. The disease was first reported in Cachar in 19734. In Bangladesh it widespread in every tea estate, especially in old plantations,

seedbaries & on unthrifty tea.

Symptoms1. The blight appears at first on the upper surface of the older & mature maintenance

leaves as minute brownish grey spots in concentric rings which increase in number & coalesce into large patches producing an undulating outline.

2. The disease patches are light to dark brown, with a grayish centre on the upper surface, roughly circular to oval, marked with concentric zonation almost from the centre to the edge.

3. The infected leaf withers & the intercostals tissue between leaf veins may fall out.

Life Cycle1. The fungus is propagated by wind-borne spores.2. Being blown onto a tea leaf, this germinates & the mycelium penetrates under the

epidermis & produces characteristic pustules, acervuli, in association with diseased grey papery tissues.

3. The acervuli are black, scattered, raised punctiform, circular in shape, convex, sub-epidermal & errumpent.

4. At maturity, conidia burst out of the acervuli.5. Conidiophores are cylindrical, hyaline or ovoid o obpyriform, 1-5 µ diameter, 10-15 µ

long.6. The conidia are fusiform, straight, 5-celled, 23-34 µ long, 6-8 µ wide; apical end of

basal cells are hyaline; apical cells having 3 appendages.7. The diseased leaf often falls off & remains attached to a healthy leaf below.8. The old leaves may break or bruise on the leaf blade.9. On young leaves, the patch is usually dark brown to almost black, irregular in shape

& not marked with concentric rings.

Fig. : Grey Blight of Tea, Pestalozia theae Sawada.

Control Measures1. Cultural Controla. Improvement of cultural practices.b. All diseased leaves should be plucked.c. Infected leaves should be swept up & burnt.d. In badly affected gardens, the pruning litters should be rigorously burnt.e. All Pluckers, should be supplied with a second should be supplied with a second bag

in which all blighted leaves should be collected.f. A systematic & through removal of blighted leaves during the plucking season, & the

burning of pruning litters.

2. Chemical Control:In severely affected section must be sprayed 1 to 2 rounds of prophylactic cum palliative spray with fungicides will also alleviate the malady.

Brown Blight:

General Description:1. The disease Brown blight is a kind of foliar disease caused by Colletotrichum

camelliae Massee is responsible for this disease.2. It prevalent in seed gardens & old plantations & often occurs conjointly with Grey

Blight disease.

Symptoms:1. The blight appears first on the upper surface of leaf as a yellowish brown patch,

narrow black spots are disturbed over the whole leaf.2. This extends to the edge of the leaf, often causes a constriction there & the affected

portion of the leaf turns over & shrievels up.3. As the fungus matures, the central portion of the leaf often falls out, leaving leaves

with large perforations.4. Portions of the leaf may dry up, starting from the leaf margin.5. The edges of the patches are sharply defined & more often marked with a delicate

concentric zone.6. The color on the upper surface is yellowish to chocolate brown at first, gradually

changing to grey from the centre outwards.7. Minute, black scattered dots appear on both sides of the diseased leaf.

Life Cycle:1. The fungus is wind-borne & infects the leaf producing acervuli. 2. Acervuli are raised, sub-epidermal, circular to oval in shape, black & thick walted.3. Acervuli burst out conidia which are oblong in shape, single celled, hyaline, being

10.8-12.3 µ × 3.09-3.39 µ in size.4. Conidiophores are simple, hyaline with hard, dark brown setae.

Fig. : Brown Blight of Tea , Colletotrichum camelliae Massee

Control Measures

Cultural Control1. Plucking the diseased leaves.2. Burning the pruning litters.3. Other sanitary measures must be taken.4. Systematic removal of the leaves from the pruning sections.

Chemical ControlChemical control methods may be adopted as per spraying calendar.

Die Back:

General Description:1. The disease Die Back is a kind of foliar disease caused by Colletotrichum

glcosporiodes is responsible for this disease.2. Die back of shoots of tea, coffee & cocoa is reported from India, Malawi & Sri Lanka.3. This often attribute to insect-attack, poor drainage, drought, lack of shade, nutritional

deficiencies etc.4. Pathological association with a fungus Colletotrichum glcosporiodes has been found

in Bangladesh tea, especially in young plantations, some clonal plants & shade trees.

Symptoms:1. The disease begins at the end of branches, hence the name Die Back.2. The fungus invades young shoots, apical stems laterals, petioles & buds of tea, shade

trees & green crops.3. A small brown spot is first seen on the soft stem enlarging into a lesion with a yellow

zone & later grinding the stem in all directions.4. The apical portion of the shoot becomes black, eventually also the petiole & bud;

young laterals show die-back.5. In severe cases, the leaves fall off within 2 weeks; 1-2 year old branches shrivel &

turn rapidly brown to black & finally die.

Life Cycle:1. The fungus propagates by means of conidia produced in numerous acervuli on

affected shoots.2. Acervuli are round, elongate or irregular in shape.3. Conidia are hyaline, cylindrical with obtuse end, aseptate, 12-12.6 µ × 4-4.8 µ av.

Size.4. Conidiophores are hyaline, cylindrical, aseptate.5. Spores are primarily wind-borne & may be disseminated by rain, dew or water-splash

etc.

Fig. : Die Back of Tea, Colletotrichum glcosporiodes

Control Measures

Cultural Control1. Minimizing water-stress by mulch or irrigation.2. Providing shade to avert sun scorch.3. Pruning cut the die back branches, 3-4 inches below the infection.

Chemical Control1. Spraying the plants immediately after pruning with a solution of copper oxychloride

(6 oz. in 12 gallons of water).2. The treatment may be repeated later in dry season when severe moisture stress first

develops.

Horse Hair Blight:

General Description:1. The disease Horse Hair Blight is a kind of Stem Disease caused by Marasmius

equicrinus Mull.2. It is wide spread in tea plantations.3. It was reported in 1900 in tea plantations of Dooars, Assam & Cachar, India & never

notiched below 4000 feet.4. This blight is prevalent in Bangladesh tea, especially in plains & shady places.

5. About 2-3% of tea bushes in old panations are not uncommonl affected withthis blight.

Symptoms: 1. Tea bushes are festooned with horse hair like threads.2. The mycelial cords are shining black & cover stems, branches, leaves & dead bark.3. In severe cases, fungal cords an inter-woven mass covering the entire foliage.4. The fungus is epiphytic, not invasive but the reduced photosynthetic surface area

causes debility of vigour & growth of bushes.

Life Cycle:1. The Fungus is known to be disseminated by means of hyphal fragments on pruning

litters, dead twigs & leaves on the ground, etc.2. The blight is more prevalent in over dense shaded & kunchi plantations where damp

situations exist.3. The perpetution of the fungus is more likely in skiffed tea as well as plantations

adjacent to bamboo baries, forest, etc.4. The blight persists through, the season, being active during the rainy season.

Control Measures:Cultural control:

1. During December-January, a thorough cleaning of tea bushes during pruning period, especially the plantations in shady & kunchi areas.

2. Dead leaves, twigs smeared with fungal threads should be removed by hand picking & burnt.

3. Better sanitation & eco-managementshould be taken.

Chemical control:1. Painting the affected frames & branches with caustic wash solution will help to

eradicate the blight.2. During June-September, the fungal threads from infected bushes in skiffed area

should be collected by hand & thereafter, spraying with 50% copper fungicide should be made under the lower canopy & towards frames & branches of the bush.

Branch & Stump Canker:

General Description:1. The disease branch & stump canker is a kind of stem disease.2. Macrophoma theicola is responsible for this disease.3. It is generally found in N.E. & S.E. India and Bangladesh.4. This pathogen penetrate through the injured part of the tea plant.5. When the tea plant break down by natural disaster then this pathogen attacked in the

plant.6. This disease is mostly common on tea in drought prone areas where soil is light,

sandy or stony.

Symptoms:1. The bark of affected tea bushes aplits; a dark sunken patch develops on the bark; old

bark falls off exposing bare wood.2. As the disease progresses in all directions, bare sunken wounds become covered at the

ridges by the growth of callus.3. The bare portion of the branch exposed by the canker is even tually attacked by wood-

rotting fungi.4. Young affected plants may die within 2-3 years.

Life Cycle:1. The fungus gain entrance through wounds caused by pruning-cuts, hail, insect injury

etc.2. The spores are exuded from spherical picnidia sunk in the bark & set new infections.3. During pruning operations, the picnidia burst out & some are liberated.4. Careless pruning & spliting of branches with blunt knives, falling of shade trees onto

tea bushes or cattle trespassing in the plantations are the main factors to develop wounds & lead to the access of the fungus.

5. Shade trees, green crops & many forest trees in tea ecosystem are also known to be the source of infection.

6. The disease becomes more acute on plantation of tillah land especially on south slopes.

Fig. : Branch & stump Canker of tea, Macrophoma theicola

Control MeasuresCultural Control

1. The affected branches should be removed with the sharp knife.2. The callus should be removed.3. The breakable part must be burnt.4. Proper mulch should be provide during drought period.

Chemical Control1. Sprayed copper fungicide as per scheduled in bush after any higher atrom or natural

disaster.2. The nacked portion of the plant should be washed with caustic wash solution within

24 hours.

Collar Canker:

General Description1. This disease is caused by Phomopsis theae.2. It is a wound parasite & occurs on tea at high elevation in India, Sri Lanka, Africa,

Kenya, Malawi, Tanzania, Uganda.3. The disease is very rare in Bangladesh tea & occassionally appears on young

seedlings & new plantations or in areas having heavy soil or hardpan beneath.

Symptoms1. The disease can attack tea at any stage of growth.2. Green succulent shoots show black lesions on stem resulting in wilting & die back .3. Later smaller branches become dry, the collar region become gridless by fungus, the

bark killed & a callus formed.4. Badly cankered branches are effectively ring-barked by the canker.5. Nodal infection & die-back of green shoots are a frequent form of attack.6. In severe cases, cankered bushes may be defoliated.

Life Cycle1. The canker infection is associated with wounds on the collar & frame of the bush

sometimes in the nodal area.2. Fructifications develop abundantly on cankered bark & appear as pimple-like pustules

or pycnidia which produce sticky picnidiospores.3. Picnidia on bark, shoots & leaves are black, conical, upto 400 µ diameter, with

protruding apical ostioles.4. Conidiospores are hyaline, simple, septate, 5-20 µ long which produe two kinds of

spores: A-conidia & B-conidia.5. A-conidia are hyaline,fusiform to ellipsoidal; B-conidia are hyaline, elongated,

filiform, curved or strongly hooked..

Fig. : Collar Canker of tea, Phomopsis theae.

Control Measures:

Cultural Control:1. Reducing the waterstress to young plantation by every means, either mulch or

irrigation will be useful.2. Avoiding the planting on thin, sandy soil is necessary.3. Pruning of young teaannually for five or six years before the drought sets in should be

practiced.

Chemical Control:1. Spraying with systeic fungicides, such as Calixin or Macuprax during the drought

periodshuld be directed towards the collar & frame of bushes only, no foliar spraying is needed.

2. Spraying the young clearings at shoot-infection stage with a copper fungicide @ 6 oz. in 10-15 gallons of water per acre every fortnight may reduce the incidence.

Red Rust:

General Description:1. The disease Red Rust is a kind of stem disease.2. This disease is caused by Cophaleuros parasiicus Karst.3. This is also called the white blight of tea.4. The blight of tea is the only algal disease.

5. It is widely distributed in the tea zones of N-E-India, Sri Lanka & Bangladesh.6. The disease is most common in young tea, old tea bushes in seedbaries & unthrifty tea sections.7. In Bangladesh tea, about 8-25% estates are affected by this blight.8. Besides tea, shade trees viz. Albizzia lebbek, A. odoratissima, A. chinesis, A. Procera, Derris robusta, Dalbargia assamica, Indigofera teysmanii & green / cover crops viz. Tephrosia candida, Crotalaria anagyroides, etc. & weeds are susceptible. Symptoms:

1. The most striking visible symptoms are the variegated leaves mottled with green, yellow & white.

2. Young leaves, specially the leaf margins become white hence it is known as white blight or leprosy.

3. Affected stems show on close examination, a dense growth of tiny, purplish red or reddish brown, hair like fructifications that resemble rusty patches hence it is misnamed as Red Rust.

4. These lessions on maturity are producing oval, purplish-black branches of algae terminate in large, readily detachable Sporangia.

5. The bark of the shoots is craked.6. Green stems become woody almost to the tip.7. Shoots become drier, cease to grow & finally die.

Life Cycle:1. Infections take place by wind-borne disease propagules in sporangia that fall onto

leaves & stems.2. The sporangia are oval, club shaped or elongate & of variable size.3. They brust out & liberate a large number of biflagillate zoospores which are motile &

capable of dispersing by means of rain splash, dew, wind etc. & enter the host plants through stomata, lenticels or wounds on leaf & stem.

4. On stems, the cortex is penetrated deeply & after pruning, the disease may prevent proliferation of shoots or cause chlorosis & defoliation.

5. Hot & wet weather are necessary for its germination.6. Debilitated, unthrifty & old plantation is more prone to attck of this blight.7. Poor soil structure & texture, low fertility, especially the lack of potassium, & high

pH, waterlogged or impervious soil layers which cause degenerative grrowth of tea bush, are considered to be predisposing factors.

8. Unshaded or poorly shaded & interplanted tea plants & stray seed baries are more vulnerable to attack.

Fig. : Red Rust of tea, Cophaleuros parasiicus Karst.

Control Measures

Cultural Control:1. Improving soil fertility by a jucidious manuring policy.2. Providing proper shade in plantation & heavy mulch will be supplemented duing

drought period.3. Improvement of drainage system in affected area should be made.

Chemical Control:1. Spraying the shade tree saplings, tea seedlings in nursery & seed baries should be

made with any 50% copper fungicide at fortnightly interval.2. Red rust affected sections should be sprayed with any approved fungicie as per list

during April-May.

Charcoal Stump Rot:

General Description:1. The disease Charcoal Stump Rot is a kind of Cosmopolitan & primary root disease.2. The pathogen, Ustulina Deusta is responsible for this disease. 3. Now, it is present in almost all the tea estates of N.E. India, Sri Lanka &Bangladesh.

4. Besides tea, the fungus is associated with a wide array of shade trees (A. Procera, Derris robusta etc.) green crops (Tephrosia candida) & many economic trres & shrubs, viz. coffee, eucalyptus,citrus etc.

Symptoms:1. Leaves become wilted, droopy & flaccid but remain attached firmly to the branches.2. Sometimes mature tea bushes die.3. Some of the branches dry up while the remainders are still green & apparently

normal.4. If bark is removed, large white or brownish-white fan-shaped patches of mycelium

are found overlying the wood.5. The wood isoften permitted by black parallel lines internally.6. The root surface bears small brownish or black isolated cushions or lamps of charcoal

like materials.

Life Cycle:1. The fungus atack lateral root contact with a diseased plant or decayed stump of tea,

shade trees or other susceptible host plants.2. Fructification are produced in abundance on dead stumps, roots etc.3. On host tissues, stromata forms discrete cushions.4. Parithecia are scattered in stroma with large ostioles.5. Ascopores are uniseriate, dark brown to black.6. Conidiophores sparsely branched.7. Conidia are hyaline, single, smooth walled.8. Spores are soil-borne & may survive for a long period in plant debris & decaying

stumps.

Fig. : Charcoal stump Rot of Tea, Ustulina Deusta

Control Measures

Cultural Control1. Dead bushes must be dug up completely & burnt on the spot.2. Shade trees should be ring barked prior to felling.3. The dead stumps & lateral roots of shade trees should be traced & extracted out as far

as possible.4. For replanting, both old tea & shade trees should be dug out & the cleared sites should

be properly rehabilitated & put under a green crop at least for one year.

Chemical Control:Affected section may be treated with 40% formaline solution @ 32 ft.oz. in 100 gallons of water & 2 gallons of the solution per plant should be applied at the collar region after forking the soil.

Violet Root:

General Description:1. This is a secondary root disease of tea.2. It is caused by Sphaerostilbe repens B. & Br.3. It is known to attack many tropical plants, such as, cocoa, coffee, rubber, papya,

avacado etc.4. The disease is well distributed in India, Africa, West Indies, Papua New Guinea &

Bangladesh.5. Besides tea, it is associated with shade trees, viz. Albizzia chinensis, A. moluccana, A.

odoratissima, A. procera, Derris robusta & green crops like Bogamedeloa, Tephrosia candida.

6. In Bangladesh tea, sometimes stray or localised incidences are observed in plantations or where water-logging or impervious layers of heavy clay soil or impeded drainage-conditions prevail.

Symptoms:1. Leaves of infected bushes look yellowish, droopy & become flaccid, sickly & fall-off

whilst green2. Secondary symptoms are yellowish & collapof the canopy.3. Roots emit a sour& rancid smell & turn violet to purplish black.4. The characteristic & conspicuous rhizomorphs are seen on stripping away the bark &

young roots are whitish & turn dark brown to purplish black.

Life Cycle:1. Rhizomorphs of the fubgus spread over the surface or into the cortex of host plants or

adjacent soil.2. Perithecia & conidia are produced on synnemata of rhizomorphs.3. Perithecia are scarlet, red to reddish brown, with a prominent neck,

500-600 × 400-450 µ dia.4. Asci are cylindrical to clavate, 185-215 × 8-9 µ, with 8 uniseriate ascospore.5. Ascospores are hyaline to light brown, rough walled, 18-20 × 8-9 µ.

Control Measures:

Cultural control:1. Ensuring that no water logging conditions prevail in tea sections.2. Drained should be properly laid out & cleaned regularly.3. Improvement of the physical conditions of soil by growing green manuring crops &

by establishing the deep rooted species of shade trees, viz. Albizzia procera & A. moluccana which are tolerant to clayey & poor drained soil.

Chemical Control:Soil treatment with 40% Formalin solution to an isolated tea section, where the disease occurs.

ConclusionThough tea is a cash crop, so we have to be careful for its proper & healthy growth. From this assignment I have gathered knowledge about the tea diseases occurred in the world. I also know about their types, symptoms of diseases, life cycle, and their control measures which is very essential for tea cultivation. If we can properly identify definite disease and take proper measures for their control, then we get maximum production of tea.

References:

1. Sana D.L. , 1989, Tea Science, Ashrafia Boi Ghar, Dhaka, Tea Disease: control guide, Page: 201-230

2. Banerjee Barundeb,1993, Tea Production & processing, IBH Publishing , New Delhi, Tea Diseases & their control, Page:243-257

3. Internet.