Plantwise Factsheets for Farmers
Potato Late Blight
Recognize the problem
fungal disease affects leaves, stems, roots and tubers of potato. It is an
important disease in Afghanistan as it causes high economic losses to farmers.
The disease is identified by black or brown spots on the underside of leaves
and stems. They are small in the beginning and appear wet. The disease spreads
quickly, as the spots become larger and destroy the leaves. The whole plant can
be destroyed within a few days. Diseased
tubers are often copper brown, reddish or purplish in colour and feel soft to
During winter, the fungus generally survives
underground in the tubers and in other host plants. The disease can be spread
by wind so it can affect neighbouring fields very quickly. Cool and moist
conditions also help to spread the disease. The fungus is washed off from the
leaves, enters the soil and infects the potato tubers. The fungus remains in
the tubers and can cause disease tp affect potato in the next season.
disease-free, healthy seeds
plant to plant distance is 25cm in a row
in recommended time for sowing
plants healthy by using balanced fertilizers
all dry plants and burn
only when plants are dead
harvesting in wet conditions
potatoes in good storage conditions with an air ventilation facility
with a fungicide like mancozeb (e.g. Dithane or manzate), metalaxl-M (e.g. Ridomil
gold) and meneb with recommended doses during all the season
the seed before sowing with fungicide like mancozeb 80% w/w @ 4 g/litre
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.
The recommendations in this factsheet are relevant to:
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