4. Early blight of potato is caused by the fungus
Alternaria solani.
First described by Ellis & Martin (1882).
Jones (1893) was the first to suggest the
name ‘early’ blight to distinguish the disease
from ‘late’ blight.
The name stems from the fact that early
blight attacks early maturing plants more
severely than medium or late maturing ones,
whereas late blight is more severe on medium
or late-maturing plant.
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5. Early blight is worldwide in distribution,
Particularly prevalent in tropical and
temperate zones.
The disease is a potential threat where
potatoes are cultivated under irrigation or
during times of heavy dew (Rotem 1994).
3
6. Appear before late blight after 4- 5 weeks
of sowing
Initial infection usually occurs on the older,
lower leaves then progresses up the plant.
Characteristic symptoms are dark brown or
black lesions with concentric rings on
leaves, which produce a ‘target spot’ effect
4
7. Chlorosis due to alternaric acid
Leaf falling
Black to brown spots on stem
Branches or plant die
Rotting in tubers
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8. It is a soil-borne disease.
The mycelium remains viable in dry infected
leaves for a year or more.
The conidia remain viable for seventeen
months in debris.
Hence the disease is readily perpetuated from
season to season.
6
9. High temperatures (80-85˚F.)
Heavy dews
Frequent rains
Overhead irrigation
High humidity
7
10. Causal Organism: Alternaria Solani
The mycelium is light brown, slender,
septate, and become dark colored with age.
8
14. Plant certified, disease-free seed in fertile, well-
drained soil.
Removal of plant residues
Eradicate weeds and volunteer solanaceous crop
plants
Store lesion-free tubers in a dry, dark, well-
ventilated location at 40° F.
Follow at least a 3-year rotation between
susceptible crops (potato, tomato, eggplant).
Spraying of fungicides
Use of resistant variety
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