| { |
| "schema_version": "1.0.0", |
| "disease_id": "corn.disease_fungal.common_rust", |
| "aliases": [ |
| "maize common rust", |
| "Puccinia sorghi rust" |
| ], |
| "crop": { |
| "common_name": "Corn", |
| "scientific_name": "Zea mays", |
| "family": "Poaceae" |
| }, |
| "condition": { |
| "common_name": "Common Rust", |
| "scientific_name": "Puccinia sorghi", |
| "alt_names": [ |
| "Maize Rust" |
| ], |
| "pathogen": { |
| "type": "disease_fungal", |
| "taxonomy": { |
| "kingdom": "Fungi", |
| "phylum": "Basidiomycota", |
| "class": "Pucciniomycetes", |
| "order": "Pucciniales", |
| "family": "Pucciniaceae", |
| "genus": "Puccinia", |
| "species": "sorghi" |
| } |
| } |
| }, |
| "issue_type": "disease_fungal", |
| "transmission": { |
| "vectors": [], |
| "dispersal": [ |
| "Wind-borne urediniospores" |
| ], |
| "overwintering": [ |
| "On alternate hosts (Oxalis spp.)", |
| "In southern regions on corn debris or volunteer corn" |
| ] |
| }, |
| "environmental_risk": { |
| "risk_factors": [ |
| "High humidity", |
| "Cool to moderate temperatures", |
| "Frequent dews or light rains", |
| "Susceptible hybrid planted" |
| ], |
| "temp_c_day": [ |
| 16, |
| 25 |
| ], |
| "temp_c_night": [], |
| "relative_humidity_pct": [ |
| 95, |
| 100 |
| ], |
| "leaf_wetness_hours_threshold": 6 |
| }, |
| "severity_rubric": { |
| "unit": "percent_leaf_area", |
| "mild": "1-5% of leaf area covered in pustules. Pustules are scattered and infrequent.", |
| "moderate": "6-25% of leaf area covered. Pustules are numerous on multiple leaves, some may be coalescing.", |
| "severe": ">25% of leaf area covered. Pustules are dense, covering large portions of leaves, leading to chlorosis, necrosis, and premature leaf death.", |
| "notes": "Severity is often assessed on the ear leaf at the R3 (milk) to R5 (dent) growth stage. Percentage refers to the symptomatic leaf area, not the whole plant." |
| }, |
| "symptoms": { |
| "leaves": [ |
| "Small, circular to oval, cinnamon-brown pustules (uredinia) appear on both upper and lower leaf surfaces.", |
| "Pustules are typically scattered randomly across the leaf, not limited by veins.", |
| "The pustules rupture the epidermis, creating a powdery, rust-colored deposit of spores.", |
| "A faint yellow or chlorotic halo may surround individual pustules.", |
| "As pustules age, they turn darker, becoming brownish-black (telia formation) late in the season.", |
| "In severe infections, leaves may become covered in pustules, leading to yellowing and premature drying." |
| ], |
| "stems": [ |
| "Pustules can occasionally appear on the husk and stalk, but are most common on leaves." |
| ], |
| "fruit": [], |
| "roots": [], |
| "whole_plant": [ |
| "In highly susceptible hybrids, severe infections can cause reduced vigor and yield loss." |
| ], |
| "signs_microscopic_or_visible": [ |
| "Cinnamon-brown, powdery urediniospores visible when pustules rupture.", |
| "Dark brown to black teliospores in older pustules (telia)." |
| ] |
| }, |
| "lookalikes": [ |
| { |
| "condition_name": "Gray Leaf Spot", |
| "condition_id": "corn.disease_fungal.gray_leaf_spot", |
| "key_differences": [ |
| "Gray leaf spot lesions are rectangular and vein-limited, while common rust pustules are oval to circular and scattered.", |
| "Common rust pustules are raised and rupture to release powdery spores; gray leaf spot lesions are flat and tan-to-gray.", |
| "Gray leaf spot lesions are typically gray or tan, not cinnamon-brown like active rust pustules." |
| ] |
| }, |
| { |
| "condition_name": "Northern Leaf Blight", |
| "condition_id": "corn.disease_fungal.northern_leaf_blight", |
| "key_differences": [ |
| "Northern leaf blight causes large, cigar-shaped, tan lesions, which are much larger than individual rust pustules.", |
| "Common rust features small, raised, powdery pustules, whereas NLB lesions are flat and necrotic.", |
| "NLB lesions do not rupture the epidermis to release powdery spores." |
| ] |
| }, |
| { |
| "condition_name": "Bacterial Leaf Streak", |
| "condition_id": "corn.disease_bacterial.bacterial_leaf_streak", |
| "key_differences": [ |
| "Bacterial leaf streak lesions are narrow, wavy-edged, and often appear water-soaked or greasy, unlike the dry, powdery rust pustules.", |
| "Bacterial lesions are translucent and yellow to brown, not the distinct cinnamon-brown of common rust.", |
| "Bacterial leaf streak does not produce raised pustules that rupture the epidermis." |
| ] |
| } |
| ], |
| "management": { |
| "cultural": [ |
| "Planting resistant or tolerant corn hybrids.", |
| "Managing alternate hosts like Oxalis spp. (wood sorrel).", |
| "Early planting to avoid high spore loads later in the season." |
| ], |
| "biological": [ |
| "Some bio-fungicides containing Bacillus species may offer suppression but are generally less effective than chemical options for severe disease pressure." |
| ], |
| "chemical": [ |
| "Application of foliar fungicides (e.g., strobilurins, triazoles, SDHIs) based on scouting and economic thresholds.", |
| "Seed treatments may provide limited early-season protection." |
| ], |
| "notes": "Fungicide application is most effective when applied early in the disease cycle, often between the VT (tasseling) and R2 (blister) growth stages, to protect the ear leaf and upper canopy." |
| } |
| } |
