Diseases
Late blight
Identify Late blight: symptoms, possible causes, prevention, and practical actions for 5 affected plants. Large, water-soaked lesions on leaves and stems
Editorial diagnosis
Diagnosis overview
Late blight is an aggressive disease of tomatoes and potatoes that can progress very quickly in wet weather.
In gardens, Late blight can occur on plants including Eggplant, potato, Pepper, Pepino. In the available profiles, it is linked mainly with Fruit vegetables, Root vegetables.
The recorded risk level is very high. Conditions that favour it include Wet weather or prolonged leaf wetness, Dense planting and poor airflow, Susceptible cultivars. Any early infection in humid mild weather is serious.
Compare upper and lower leaf surfaces, the boundary between healthy and damaged tissue, and spread after wet weather. Coatings, spores, or progressive rot support a disease diagnosis.
A common mistake is to identify a disease from one spot alone; weather, spread, and pathogen structures also need to fit.
At a glance
Plants
5
Category
Fruit vegetables, Root vegetables
Risk
very high
Scientific name
Phytophthora infestans
Typical signs
- Brown leaf lesions
- Dark stems
- Brown fruit patches
- Rapid spread in moisture
Possible confusion
- Growing problem: Growing problems are usually linked to water, light, temperature, or soil and do not show pathogen growth, pustules, or progressive infection patterns.
- Nutrient deficiency: Deficiency patterns are often more regular and follow leaf age or veins. Diseases more often show spots, coatings, rot, wilting, or pathogen structures.
Immediate actions
- Remove affected plant parts
- Improve airflow
- Avoid overhead watering
- Keep tools clean
- Remove heavily infected plant residues
Prevention
- Use suitable spacing
- Follow crop rotation
- Choose robust cultivars
- Keep leaves dry
- Support soil structure and plant vigour
Affected plants
Guides
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