Xanthomonas campestris pv. vesicatoria
All stages of growth are susceptible and all portions of
the plant may show symptoms.
On leaves, the lesions are sunken on the top surface
and slightly raised on the lower surface. The lesions
are brown, circular to irregular, water-soaked, and
usually smaller than 3 mm in diameter (sometimes
larger in hot, humid conditions). When numerous lesions
occur, they coalesce causing necrotic areas, and give
the plants a blighted appearance (see photo at top right).
Affected leaves may turn yellow and drop off or become
dry and remain on the plant. Severe infections can result
in defoliation of the plant. Affected seedlings develop
yellow spotting and may defoliate when infection is
Diseased stems and petioles have elliptical, raised
lesions. Flower infection results in severe blossom drop.
On young fruit, lesions are small, circular, green
spots reaching a diameter of 2–3 mm. They become
brown and have a raised, coarse, wart-like surface. Ripe
fruit are rarely infected.
How to Identify Bacterial Spot
Lesions begin as small
spots, which are raised
on the lower surface
Raised, brown, wart-like lesions on fruit
Severe infection leads
Written by Ray Cerkauskas, Visiting Scientist from Agriculture and Agri-Food Canada. Edited by Tom Kalb. Photos by T.A. Kucharek,
B.H. Chew and Glen L. Hartman. 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; www: www.avrdc.org
Conditions for Disease Development
Young leaves and fruit are more susceptible to infection
than older tissue. The pathogen is seed borne and can
infect new seedlings from infected crop debris left in
the soil after harvest or on pepper volunteers. The
pathogen cannot live long in the soil without crop debris
to live on. Weeds such as black nightshade can also
harbor the pathogen and transmit it to new plants.
The bacterium is more common on t