Late blight: – Potato and Tomato’s

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Late blight disease is caused by bacteria in plants

Late blight is caused by the fungal-like oomycete pathogen Phytophthora infestans. The primary host is potato, but also can infect other solanaceous plants, including tomatoes, petunias and hairy nightshade. These infected species can act as source of inoculum to potato.

Late blight Disease symptoms:

This disease damages leaves, stems and tubers. Affected leaves appear blistered as if scalded by hot water and eventually rot and dry out.

When drying out, leaves turn brown or black in color. When infections are still active, spots appear on the underside of leaves blanketed in what looks like flour.

Affected stems begin to blacken from their tips, and eventually dry out.

Severe infections cause all foliage to rot, dry out and fall to the ground, stems to dry out and plants to die.

Affected tubers display dry brown-colored spots on their skins and flesh. This disease acts very quickly. If it is not controlled, infected plants will die within two or three days.

Late blight imgSurvival and spread:

The pathogen survives in plant debris in the soil.

It spreads through soil and infected seed tubers.

Favourable condition:

High humidity

Low temperature and leaf wetness


Chemical Control

Late blight is controlled by eliminating cull piles and volunteer potatoes, using proper harvesting and storage practices, and applying fungicides when necessary. Air drainage to facilitate the drying of foliage each day is important.

Spraying fungicides is the most effective way to prevent late blight. For conventional gardeners and commercial producers, protectant fungicides such as chlorothalonil and Mancozeb can be used.


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1 Comment

  • Deepa Singh
    December 31, 2022 @ 4:06 pm

    Nice very useful information

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