Ppt on Major Diseases Of Tea: Symptoms, Causal Agents And Management Strategies

This presentation provides an overview of major diseases affecting tea (Camellia sinensis), focusing on their pathogens, symptoms, disease cycles, and management strategies. Emphasis is placed on integrated disease management, including cultural, chemical, and biological control methods, which are essential for sustainable tea production and plant health.
Introduction to Tea and Its Diseases
  • Botanical name: Camellia sinensis
  • Chromosome number: 2n = 30
  • Origin: China
  • Tea is susceptible to various fungal, algal, and oomycete diseases affecting yield and quality.
  • Effective disease management is crucial for sustainable tea cultivation.
Algal Leaf Spot
Pathogen: Cephaleuros virescens
Nature: Algal disease
Symptoms:
  • Circular, raised, purple to reddish-brown lesions on leaves.
  • Older spots become greenish-gray, resembling lichen.
  • Most lesions develop on upper leaf surface; rarely harmful to plant vigor.
Disease Cycle:
  • Alga produces rust-colored spore-like bodies on leaf spots.
  • Dispersed by wind or rain; favored by high humidity and poor drainage.
Management:
  • Avoid plant stress and poorly drained sites.
  • Promote air circulation; prune and destroy infected parts.
  • Apply Bordeaux mixture; improve soil nutrition (NPK).
Brown Blight and Grey Blight
Pathogens: Colletotrichum spp. (Brown blight), Pestalotiopsis spp. (Grey blight)
Nature: Fungal leaf spots
Symptoms:
  • Small, oval, pale yellow-green spots on young leaves.
  • Spots enlarge, turn brown/gray with concentric rings and black dots.
  • Leads to defoliation; affects leaves of all ages.
Disease Cycle:
  • Fungal spores in black dots on lesions.
  • Spread by rain splash; infect new leaves under wet conditions.
Management:
  • Avoid plant stress; ensure adequate spacing for air flow.
  • Spray Copper Oxychloride or Bordeaux mixture (0.1%) in winter and summer.
Blister Blight
Pathogen: Exobasidium vexans
Nature: Fungal disease
Symptoms:
  • Pinhole-sized spots on young leaves (<1 month old).
  • Spots enlarge, become transparent, then light brown.
  • Blister-like symptoms with water-soaked zones; blisters turn white and velvety, then brown.
  • Young stems may bend, break, or die.
Disease Cycle:
  • Continuous cycle in wet conditions; spores dispersed by wind.
  • Direct penetration of leaf tissue; symptoms in 10 days.
Management:
  • Prune and destroy affected leaves and shoots.
  • Spray Bordeaux mixture, Copper Oxychloride (0.1%), or triazole fungicides (e.g., hexaconazole).
  • Apply fungicides at 5-day intervals during rainy season.
Horse Hair Blight
Pathogen: Marasmius crinisequi
Nature: Fungal disease
Symptoms:
  • Black, hair-like fungal threads on upper branches and twigs.
  • Rapid leaf drop due to volatile substances produced by fungus.
Disease Cycle:
  • Spread via extension of hair-like threads from infected to healthy twigs.
Management:
  • Remove and destroy crop debris.
  • Prune out infected or dead branches.
Camellia Flower Blight
Pathogen: Ciborinia camelliae
Nature: Fungal disease
Symptoms:
  • Small, brown, irregular spots on flower petals.
  • Whole flower turns brown and drops prematurely.
Disease Cycle:
  • Emerges in early spring during high moisture periods.
Management:
  • Remove infected flowers and crop debris.
  • Apply soil drenches with suitable fungicides.
Twig Dieback and Stem Canker
Pathogen: Macrophoma theicola
Nature: Fungal disease
Symptoms:
  • Browning and drooping of leaves; shoots dry and die.
  • Cankers form on branches; tip dieback.
Disease Cycle:
  • Spores produced on dead branches; spread by rain splash.
  • Entry through wounds; survives on pruned branches.
Management:
  • Plant in well-drained, acidic soils.
  • Remove diseased twigs below cankered areas; disinfect tools.
  • Apply protective fungicides during wet weather.
Black Root Rot
Pathogen: Rosellinia arcuata
Nature: Fungal root disease
Symptoms:
  • Originates from dead leaves above soil; spreads to roots.
  • Star-like mycelium under bark; mycelium surrounds stem base.
  • Swollen ring of tissue above dead patch.
Management:
  • Remove and destroy infected plants.
  • Practice clean cultivation; remove fallen leaves.
  • Dig trenches around infected bushes to expose soil to sunlight.
Camellia Dieback and Canker
Pathogen: Glomerella cingulata (Colletotrichum gloeosporioides, sexual stage)
Nature: Fungal disease
Symptoms:
  • Sudden yellowing and wilting of leaves; branch tip dieback.
  • Gray blotches and sunken cankers on bark and stem.
  • Cankers girdle stem; upper parts lose vigor and die.
Comments:
  • Fungus enters through wounds; symptoms worsen in hot, dry weather.
Management:
  • Plant in well-drained, acidic soils.
  • Remove diseased twigs below cankers; disinfect tools.
  • Apply protective fungicides during wet periods.
Root Rot
Pathogen: Phytophthora cinnamomi
Nature: Oomycete root disease
Symptoms:
  • Yellowing leaves; poor growth; wilting; discolored roots; rapid plant death.
Comments:
  • Favored by poorly drained, warm soils.
Management:
  • Plant in well-drained soils; avoid waterlogging.
  • Apply appropriate fungicides to protect plants.
Poria Root Disease (Red Root Disease)
Pathogen: Poria hypolateritia
Nature: Fungal root disease
Symptoms:
  • Yellowing foliage; wilting or sudden death of plant parts.
  • Withered leaves remain attached; red discoloration of roots; whitish mycelium visible.
Comments:
  • Spread by mycelial strands in soil.
Management:
  • Remove infected bushes and adjacent symptomatic plants.
  • Remove all living/dead roots and stumps; destroy by burning.
  • Treat surrounding bushes to prevent spread.
Wood Rot Disease
Pathogen: Hypoxylon spp.
Nature: Fungal wood rot
Management:
  • Apply Benomyl or Copper Oxychloride (0.01%).
  • Use botanical extracts (e.g., Azadirachta, A. nilagirica) at 10% concentration.
  • Apply biocontrol agents (Bacillus sp., Pseudomonas sp., Trichoderma viride).
Sclerotial Blight
Pathogen: Sclerotium rolfsii
Nature: Fungal disease
Management:
  • Use Bacillus megaterium as a plant growth promoter and biocontrol agent.
  • Induces systemic resistance and reduces disease incidence.
Black Rot Disease
Pathogen: Various (including mycoflora from tea environment)
Nature: Fungal disease
Management:
  • Apply antagonistic fungi (e.g., Aspergillus niger, Trichoderma atroviride, T. citrinoviride) as foliar sprays.
  • Reduces symptom severity and disease index.
Integrated Disease Management in Tea
  • Combine cultural, chemical, and biological control methods for sustainable management.
  • Use resistant varieties where available.
  • Maintain field hygiene: remove debris, prune infected parts, ensure proper spacing.
  • Apply fungicides judiciously to avoid resistance.
  • Promote beneficial microorganisms for biocontrol.

Objective Questions

Q1. What is the scientific name of tea?
A. Camellia sinensis
B. Camellia japonica
C. Thea assamica
D. Thea viridis
Answer: A

Q2. Which pathogen causes algal leaf spot in tea?
A. Exobasidium vexans
B. Cephaleuros virescens
C. Colletotrichum sp.
D. Marasmius crinisequi
Answer: B

Q3. What is a common management practice for brown blight in tea?
A. Spray Bordeaux mixture
B. Apply neem oil
C. Use sulfur dust
D. Flood irrigation
Answer: A

Q4. Which disease is characterized by black fungal threads resembling horse hair?
A. Blister blight
B. Horse hair blight
C. Camellia flower blight
D. Twig dieback
Answer: B

Q5. Which chemical fungicide was found effective against wood rot disease in tea?
A. Benomyl
B. Mancozeb
C. Carbendazim
D. Metalaxyl
Answer: A

Q6. What symptom is typical of blister blight in tea?
A. Black dots on leaves
B. Blister-like symptoms on young leaves
C. Star-like mycelium on roots
D. Yellowing of flower petals
Answer: B

Q7. Which organism is a good plant growth promoter and reduces sclerotial blight in tea?
A. Bacillus megaterium
B. Pseudomonas sp.
C. T. viride
D. A. niger
Answer: A

Q8. Which disease is caused by Phytophthora cinnamomi in tea?
A. Root rot
B. Brown blight
C. Black root rot
D. Camellia dieback
Answer: A

Q9. What is a recommended management for Poria root disease in tea?
A. Remove infected bushes and adjacent plants
B. Increase irrigation frequency
C. Apply potassium nitrate
D. Spray insecticides
Answer: A

Q10. Which fungicide is a promising triazole against blister blight of tea?
A. Hexaconazole
B. Copper oxychloride
C. Tridemorph
D. Benomyl
Answer: A