| { |
| "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." |
| } |
| } |
