Service to manage wildlife disease - AFGRI

PLANT DISEASES
JE van der Waals, University of Pretoria
Early blight is one of the major foliar diseases of potatoes.
Without adequate control, it can cause devastating yield
losses. The importance of the disease should therefore not
be underestimated.
Early blight symptoms on potato plants in the field.
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Early blight lesion on a potato leaf, showing concentric rings.
Early blight causes premature defoliation of potato plants in
most areas where potatoes are grown, but is especially prevalent
in the tropics and temperate zones. The disease, with the fungus
Alternaria solani as the causal agent, is a potential threat where
potatoes are grown under irrigation or during times of heavy
dew. Early blight is prevalent in all provinces in South Africa
and is a limiting factor in production in late summer.
The primary damage of early blight is due to premature
defoliation of the plant. Photosynthesis rates increase and
respiration rates decrease in apparently healthy tissues. Heavy
infection early in the growing season can cause yield losses
of 20% to 50%.
SYMPTOMS
Characteristic symptoms, which are similar on all hosts, are
dark brown or black lesions with concentric rings on older or