Below is a comprehensive and detailed catalog of major leaf diseases, categorized by pathogen type—fungal, bacterial, viral, parasitic, physiological, and nutrient-related. For each disease, you’ll find the name, causal agent, host plants, symptoms, conditions favoring the disease, host age, seasonality, potential impact, and treatment or prevention methods.
🍄 I. Fungal Leaf Diseases
Disease Name (EN) | Latin Pathogen | Host Plants | Symptoms | Favorable Conditions | Age Affected | Season | Impact Severity | Treatment/Control |
---|---|---|---|---|---|---|---|---|
Leaf Blight | Alternaria spp. | Cabbage, tomato, onion | Dark concentric rings on leaves | Warm, humid | All | Summer | Medium | Mancozeb, improve airflow |
Leaf Spot | Cercospora spp. | Sugar beet, soybean, rice | Small circular spots with halos | Wet weather | All | Rainy season | Medium–High | Chlorothalonil, crop rotation |
Powdery Mildew | Erysiphe sp., Oidium sp. | Grapevine, pumpkin, rose | White powder, yellowing leaves | High humidity, low wetness | All | Late summer | Medium | Sulfur, potassium bicarbonate |
Downy Mildew | Peronospora sp., Plasmopara sp. | Grapes, lettuce, maize | Gray fuzz, chlorotic patches | Cool nights, dew | All | Spring–Summer | High | Metalaxyl, copper fungicides |
Anthracnose | Colletotrichum spp. | Mango, beans, tomato | Sunken lesions, fruit involved | Rainy, leaf wetness | Fruit trees | Onset of rains | Medium–High | Azoxystrobin, avoid overhead watering |
Septoria Leaf Spot | Septoria lycopersici | Tomato | Small black spots, yellow halo | Cool, persistent wetness | Mature plants | Early wet season | Medium | Copper sprays, straw mulch |
Rust | Puccinia spp., Uromyces spp. | Wheat, soybean, beans | Orange/brown pustules on lower leaves | Warm, damp | All | Summer | Medium–High | Sulphur, resistant cultivars |
Leaf Rust | Melampsora spp. | Poplar, willow | Orange pustules, defoliation | Cool spring, wet | Trees/shrubs | Spring | Medium | Fungicide, resistant clones |
🧫 II. Bacterial Leaf Diseases
Disease Name | Latin Pathogen | Hosts | Symptoms | Conditions | Season | Impact | Treatment |
---|---|---|---|---|---|---|---|
Bacterial Leaf Spot | Xanthomonas spp. | Pepper, tomato, rice | Water-soaked lesions, yellow halo | Rain splash, warm days | Summer | Medium | Copper oxychloride, hot water seed treatment |
Bacterial Blight | Pseudomonas syringae pathovars | Beans, cucurbits | Angular necrotic spots, water-soaking | Cool, wet periods | Spring–Fall | Low–Medium | Copper + streptomycin, pathogen-free seed |
Bacterial Leaf Scorch | Xylella fastidiosa | Almond, oak, plum | Scorched leaf margins, decline | Warm, vector-borne | Summer | Medium | Xylem flush, leaf removal |
Bacterial Wet Leaf | Erwinia amylovora | Apple, pear | Ooze, browning blossoms/leaves | Warm wet weather | Spring | Medium | Streptomycin, sanitizer sprays |
🌱 III. Viral Leaf Diseases
Disease | Latin Pathogen | Hosts | Symptoms | Transmission | Season | Impact | Control |
---|---|---|---|---|---|---|---|
Mosaic Virus | TMV, CMV, etc. | Cucumber, tobacco, squash | Mosaic patterns, distorted leaves | Insects, seed, sap | Year-round | High | Resistant varieties, insect control |
Leaf Curl | Taphrina deformans | Almond, peach | Curled, thickened, pinkish leaves | Moist cool spring | Spring | Medium | Curative copper sprays |
Yellow Mosaic | Potyvirus spp. | Bean, soybean | Yellow mosaic streaks | Aphid vectors | Early summer | Medium | Insecticides, resistant seeds |
🐛 IV. Parasitic and Infestation-Related Leaf Damage
Issue | Parasite | Hosts | Symptoms | Season | Control |
---|---|---|---|---|---|
Leaf Gall | Meloidogyne spp. (nematode) | Oak, hickory, grapevine | Galls on leaves, twisted growth | Growing season | Acaricides, root nematicides |
Leaf Miner | Liriomyza sp. | Tomato, cucurbits | Serpentine mines, feeding damage | Summer | Insecticides, pheromone traps |
Scale Insect Damage | Coccoidea family | Citrus, ornamentals | Yellowing leaves, sticky honeydew | All seasons | Oils, systemic insecticides |
🌊 V. Physiological Leaf Disorders
Condition | Cause | Hosts | Symptoms | Season | Remedy |
---|---|---|---|---|---|
Sunburn/Leaf Scorch | UV & heat | Orchards, ornamentals | Bleached blotches, crisp edges | Summer | Shade cloth, whitewash |
Herbicide Injury | Chemical drift | Many crops | Distorted, crinkled, bleached leaves | Application periods | Buffer zones, spray formulator |
🥦 VI. Nutrient Deficiency Leaf Symptoms
Nutrient | Leaf Appearance | Affected Plants | Solution |
---|---|---|---|
Nitrogen (N) | Uniform pale green/yellow leaves | Corn, leafy vegetables | Apply urea or ammonium sulfate |
Magnesium (Mg) | Interveinal chlorosis | Citrus, potatoes | Apply magnesium sulfate |
Iron (Fe) | Interveinal yellowing on young leaves | Citrus, blueberry | Foliar chelated iron |
Calcium (Ca) | Tip/edge necrosis | Tomatoes, strawberries | Foliar Ca sprays, consistent watering |
Zinc (Zn) | Rosetting, stunted leaves | Maize, beans | Foliar ZnO or ZnSO₄ |
📊 Disease Overview by Type
Disease Type | Common Examples | Risk Level | Control Strategy |
---|---|---|---|
Fungal | Blight, Mildews, Rust | Medium–High | Fungicides, resistant varieties |
Bacterial | Spot, Blight, Scorch | Medium | Copper agents, hygiene |
Viral | Mosaic, Curl | High | Insect control, resistant lines |
Parasitic | Leaf gall, Miner | Low–Medium | Pesticides, cultural disruption |
Physiological | Sunburn, Drift injury | Low | Cultural controls |
Nutrient deficiency | Yellowing, chlorosis | Low | Fertilization, soil management |
🛠️ Management Recommendations
Routine monitoring for early signs on leaves.
Integrated treatment using chemical, biological, and cultural methods.
Fungicide/ bactericide rotation to prevent resistance.
Multispecies cropping and crop rotation to reduce pathogen buildup.
Use of resistant cultivars and maintaining soil fertility for plant vigor.
Proper irrigation practices—avoid overhead watering and excessive moisture.
Quarantine practices for imports to avoid new pathogens.