🍅 Tomato How hard it is to control: ★★★★★ 5/5

Late blight on tomato

One of the most dangerous tomato diseases, caused by an oomycete (fungal-like organism). Without intervention can lead to complete yield loss. Less common in greenhouse cultivation.

Symptom photos

Late blight — Leaf — patch of rot with a paler, sporulating margin — Leaf — patch of rot with a paler, sporulating margin Photo: Scot Nelson from Honolulu, Hawaii, USA, licence CC0

Late blight — Fruits — firm, brown patches of rot on green tomatoes — Fruits — firm, brown patches of rot on green tomatoes Photo: Rasbak at Dutch Wikipedia, licence CC BY-SA 3.0

Late blight — Shoot — curling, browning leaves with grey mould — Shoot — curling, browning leaves with grey mould Photo: Scot Nelson from Honolulu, Hawaii, USA, licence CC BY-SA 2.0

Late blight — Early stage — a single grey-green patch on the leaf blade — Early stage — a single grey-green patch on the leaf blade Photo: Dwight Sipler from Stow, MA, USA, licence CC BY 2.0

Late blight — Leaf — greasy grey-green patches with white mould underneath — Leaf — greasy grey-green patches with white mould underneath Photo: Goldlocki, licence CC BY-SA 3.0

Late blight — Truss — brown rot of the fruits and dying leaves — Truss — brown rot of the fruits and dying leaves Photo: Goldlocki, licence CC BY-SA 3.0

Late blight — Fruit — advanced rot covered in white mycelium — Fruit — advanced rot covered in white mycelium Photo: Mary Ann Hansen, Virginia Polytechnic Institute and State University, United States, licence CC BY 3.0 us

Late blight — Fruit — greasy brown-green patch (two views) — Fruit — greasy brown-green patch (two views) Photo: Downtowngal, licence CC BY-SA 3.0

Late blight — Fruit — extensive, marbled patch of rot — Fruit — extensive, marbled patch of rot Photo: Downtowngal, licence CC BY-SA 3.0

Late blight — Fruit on the plant — dark brown patch of rot — Fruit on the plant — dark brown patch of rot Photo: Benutzer:CMEW, licence CC BY-SA 3.0

Late blight — Stem — dark brown rot girdling the shoot — Stem — dark brown rot girdling the shoot Photo: Dwight Sipler from Stow, MA, USA, licence CC BY 2.0

Late blight — Truss — brown patches on ripening fruits — Truss — brown patches on ripening fruits Photo: Rasbak, licence CC BY-SA 3.0

Late blight — Truss — sporulating fruit rot and dried-up leaves — Truss — sporulating fruit rot and dried-up leaves Photo: Scot Nelson from Honolulu, Hawaii, USA, licence CC0

Late blight — Leaves — extensive brown necrosis with yellowing — Leaves — extensive brown necrosis with yellowing Photo: Scot Nelson from Honolulu, Hawaii, USA, licence CC0

Symptoms

Dark green, watery, then browning spots on leaves
Extensive brown necrosis on stems
Gray-green, then brown spots on fruits
White coating on the border of healthy and diseased tissue
Symptoms similar to burning in greenhouses

What it does to the crop

Yield losses 50-100% depending on occurrence time
Complete plant die-back without intervention
Fruit rot
Very rapid spreading

What encourages it

High air humidity
Prolonged leaf wetness
Temperature below 12-15°C favors indirect germination (zoospores)
Temperature above 15°C favors direct sporangial germination (optimum 20-24°C)

Prevention

Location away from water bodies
Avoiding proximity to potato plantations
Tolerant varieties
Low air humidity
Frequent inspection (min. 2 times/week)

⚠️ Before you reach for a spray

This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.

Keep the disease atlas with you in the garden

In the app you can identify a disease from photos, work out the spray dose for your own bed and log the treatment in your task calendar. Free, no sign-up, works offline.

Open the atlas in the app →

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