{
  "schema_version": "1.0.0",
  "disease_id": "tea.disease_fungal.leaf_blight",
  "aliases": [
    "tea anthracnose",
    "bird's eye spot of tea",
    "target spot of tea"
  ],
  "crop": {
    "common_name": "tea",
    "scientific_name": "Camellia sinensis",
    "family": "Theaceae"
  },
  "condition": {
    "common_name": "leaf blight",
    "scientific_name": "Colletotrichum gloeosporioides (teleomorph: Glomerella cingulata)",
    "alt_names": [
      "Pestalotiopsis theae"
    ],
    "pathogen": {
      "type": "disease_fungal",
      "taxonomy": {
        "kingdom": "Fungi",
        "phylum": "Ascomycota",
        "class": "Sordariomycetes",
        "order": "Glomerellales",
        "family": "Glomerellaceae",
        "genus": "Colletotrichum",
        "species": "gloeosporioides"
      }
    }
  },
  "issue_type": "disease_fungal",
  "transmission": {
    "vectors": [
      "rain splash",
      "wind",
      "insects (mechanical)"
    ],
    "dispersal": [
      "conidia (asexual spores)",
      "contaminated pruning tools",
      "human movement"
    ],
    "overwintering": [
      "infected fallen leaves",
      "cankers on stems",
      "dormant mycelium in plant debris"
    ]
  },
  "environmental_risk": {
    "risk_factors": [
      "prolonged periods of high humidity",
      "frequent rainfall",
      "poor air circulation in dense canopies",
      "wounds from pruning or pests",
      "nutrient stress"
    ],
    "temp_c_day": [
      20,
      30
    ],
    "temp_c_night": [],
    "relative_humidity_pct": [
      85,
      100
    ],
    "leaf_wetness_hours_threshold": 8
  },
  "severity_rubric": {
    "unit": "percent_leaf_area",
    "mild": "Fewer than 5 lesions per leaf, or < 5% of the total leaf area is symptomatic.",
    "moderate": "Multiple lesions, some may be coalescing, covering 5-25% of the total leaf area.",
    "severe": "Large, coalesced lesions covering > 25% of the leaf area, often leading to leaf distortion, withering, and premature defoliation.",
    "notes": "Severity is estimated based on the percentage of symptomatic tissue on visible leaves in an image. It can be assessed on an individual leaf or averaged across the plant canopy."
  },
  "symptoms": {
    "leaves": [
      "Initial symptoms are small, water-soaked, yellowish-brown spots, often on mature leaves.",
      "Spots enlarge to form circular or irregular lesions, typically 2-10 mm in diameter.",
      "Mature lesions develop a characteristic pale gray, tan, or whitish center.",
      "A distinct, raised, dark brown or purplish-brown border surrounds the pale center.",
      "Concentric rings are often visible within the lesion, creating a 'target' or 'bull's-eye' appearance.",
      "Multiple lesions can merge (coalesce) to form large, irregular blighted patches.",
      "In severe infections, the entire leaf may turn brown, curl, and drop prematurely.",
      "Lesions may crack or fall out, creating a 'shot-hole' effect."
    ],
    "stems": [
      "In severe cases, cankers or dieback can occur on young shoots and twigs."
    ],
    "fruit": [],
    "roots": [],
    "whole_plant": [
      "Reduced vigor and defoliation in heavily infected bushes.",
      "Overall thinning of the plant canopy."
    ],
    "signs_microscopic_or_visible": [
      "Under humid conditions, tiny black dots (acervuli, the fungal fruiting bodies) may appear arranged in concentric rings within the pale center of lesions.",
      "During wet periods, pinkish or salmon-colored spore masses may ooze from the acervuli."
    ]
  },
  "lookalikes": [
    {
      "condition_name": "gray_blight",
      "condition_id": "tea.disease_fungal.gray_blight",
      "key_differences": [
        "Gray blight lesions are often larger, more uniformly gray or brownish, and may lack the distinct, dark, raised border of leaf blight.",
        "Gray blight lesions typically have a more 'sooty' appearance due to numerous black pycnidia scattered across the surface, rather than arranged in rings.",
        "The 'target' or 'bull's-eye' pattern is much more characteristic of leaf blight than gray blight."
      ]
    },
    {
      "condition_name": "helopeltis_damage",
      "condition_id": "tea.pest_insect.helopeltis_damage",
      "key_differences": [
        "Helopeltis damage results from insect feeding punctures, creating initially water-soaked spots that quickly turn dark brown or black and become sunken.",
        "Lesions from Helopeltis are often more angular and do not typically develop pale centers or concentric rings.",
        "No fungal signs (like acervuli or spore masses) are present in Helopeltis lesions."
      ]
    },
    {
      "condition_name": "algal_leaf_spot",
      "condition_id": "tea.disease_algal.algal_leaf_spot",
      "key_differences": [
        "Algal spots are superficial and slightly raised from the leaf surface with a velvety or crusty texture.",
        "Algal spots are typically greenish-gray to orange-red in color, not the tan/gray center with a dark border typical of leaf blight.",
        "Leaf blight lesions are necrotic and sunken into the leaf tissue, whereas algal spots grow on the surface."
      ]
    }
  ],
  "management": {
    "cultural": [
      "Prune and remove infected leaves and twigs to reduce inoculum.",
      "Ensure proper plant spacing and canopy management to improve air circulation and reduce humidity.",
      "Avoid overhead irrigation to minimize leaf wetness duration.",
      "Maintain balanced plant nutrition to improve host resistance."
    ],
    "biological": [
      "Application of biocontrol agents such as *Trichoderma* spp. or *Bacillus subtilis* can help suppress the pathogen."
    ],
    "chemical": [
      "Apply protective fungicides, such as copper-based compounds, mancozeb, or chlorothalonil, especially during periods favorable for disease development.",
      "Systemic fungicides like carbendazim or thiophanate-methyl may be used for curative action, subject to local regulations and resistance management."
    ],
    "notes": "An integrated pest management (IPM) approach combining cultural, biological, and chemical methods is most effective. Fungicide application should be timed based on weather forecasts and disease pressure."
  }
}