Xanthomonas campestris pv. vesicatoria
Found worldwide, most severe in the tropics and subtropics
Foliar lesions are dark, circular, water-soaked, and
usually smaller than 3 mm in diameter. They are greasy
in appearance on the top surface. The lesions become
brown-black and angular in shape. The center of the
spots may dry and fall out. When numerous lesions
occur (often during wet conditions), lesions may
coalesce and give plants a blighted appearance.
Affected leaves may turn yellow and drop off or become
dry and remain on the plant. Lesions are generally more
numerous on young tissue that is more susceptible
compared to old tissue.
Affected seedlings become more spotted with leaf
yellowing and in severe stages with defoliation. Infected
stems and petioles are similar to those found on leaves,
but are elliptical in shape.
Symptoms also appear on immature fruit. Lesions
begin as small, raised, black specks surrounded by a
water-soaked border, enlarging to become brown,
slightly sunken, scabby spots, sometimes surrounded
Initital symptoms are tiny, circular, dark lesions on leaves (left photo). Lesions may coalesce, causing
blighted areas on leaves (center photo). Immature fruit show brown, slightly sunken, scabby spots. Lesions
on stems are elliptical in shape (right photo).
How to Identify Bacterial Spot
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
by a halo. The spots are not deep and do not usually
lead to rot. Ripe fruit are rarely infected.
Conditions for Disease Development
Infected crop debris is often the source of the disease
in a new crop. The pathogen cannot survive long in the
soil without crop debris to live on. Weeds such as black
nightshade and volunteer tomato plants can also harbor
the pathogen and transmit it to health