World Vegetable Center
The leaves, stems and fruit on the vine may be affected.
Symptoms on leaves are most likely to appear on the
older foliage. Small dark spots enlarge into circular
lesions consisting of concentric rings. The tissue
surrounding the lesions becomes yellow and the spots
later become irregular in shape. The leaf becomes
yellow as greater parts of the tissue are affected. The
lesions turn brown and eventually drop from the plant.
Defoliation occurs under prolonged periods of leaf
wetness and high temperatures; exposed fruit become
susceptible to sunburn damage.
Leaf lesions arising from Septoria lycopersici,
another foliar pathogen of tomato, may be confused
with early blight symptoms. However, Septoria lesions
are lighter tan in color with a small pepper-like fruiting
body in the center of the lesion, and the disease
generally arises under cooler temperatures than with
the case of early blight.
Stems and petioles affected by early blight have
elliptical concentric lesions, which drastically weaken
the plant. Lesions at the base of emerging seedlings
can cause a collar rot. If this arises simultaneously on
many seedlings, it may indicate contamination of tomato
seeds or soil used for planting.
Mature and ripe fruit may be affected. Lesions occur
Lesions on leaves have concentric rings surrounded by yellowing tissue (left photo). Dark concentric rings
develop on the stem end of fruit (right photo).
How to Identify Early Blight
Written by Ray Cerkauskas, Visiting Scientist from Agriculture and Agri-Food Canada. Edited by Tom Kalb.
Published by AVRDC – The World Vegetable Center; P.O. Box 42, Shanhua; Taiwan 741; ROC.
tel: (886-6) 583-7801; fax: (886-6) 583-0009; email: firstname.lastname@example.org; web: www.avrdc.org
on the stem end or the upper shoulder and may be
quite large. Fruit wounds or cracks may also have
large, dark, leathery, sunken areas with concentric
Conditions for Disease Development
The disease is favored by war