Bacterial Spot of Pepper and Tomato
Vegetable Disease Information Note 18
David F. Ritchie, Extension Plant Pathologist
Charles W. Averre, Extension Plant Pathologist
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leafspot is a severe disease of peppers and tomatoes in North Carolina.
It is more prevalent during wet seasons. Damage to the plants includes
leaf and fruit spots which result in reduced yields, defoliation, and
sun scalded fruit.
spot of peppers and tomatoes can be recognized by numerous angular spots
on the leaves. Initially, the spots are water-soaked. Leaves infected
at an early stage become deformed. Often, the margins of affected leaves
are rimmed with a narrow band of necrotic
tissue. Infected pepper leaves drop prematurely; this exposes fruit to
sun and may result in sun scald, secondary fruit rots, and reduced yields.
Bacterial spots on the fruit are at first small, blister-like and irregular,
and later turn brown and develop a warty appearance.
is caused by the bacterium Xanthomonas campestris pv. vesicatoria
(proposed names, X. vesicatoria and X. axonopodis
pv. vesicatoria). The bacteria are microscopic and occur in enormous
numbers in affected areas. They are rod-shaped and have a long whip-like
tail that propels them in water; this helps them invade wet leaves and
The disease is widespread in tomatoes and peppers in the southeastern
United States. Bacteria may overwinter in infested plant debris one year.
The most important means of overwintering, however, is in seed.
In North Carolina, most disease outbreaks can be traced to the use of
infected seed or diseased transplants. Lesions may be observed
on cotyledons of seedlings. Once initial infections take place, it can
spread rapidly throughout the entire field during rainy weather from a
few infected plants. Spread in plant beds/greenhouses and during planting
operations is especially serious.
movement from one leaf or plant to another, such as splashing rain drops,
overhead irrigation, and touching or handling wet plants, may spread the
bacteria from diseased to healthy plants. Bacteria then enter the leaf
through stomates, hydathodes at leaf margins, and damaged epidermal cells
and cause new spots. The longer the plants are wet, the greater is the
opportunity for infection to occur. If a protective film of copper fungicide
is on plant surfaces, most bacterial cells will be killed before gaining
entry into the leaf or fruit -- hence, the importance of applying sprays
before and during rainy periods. Sprays are not effective against bacteria
inside the tissue.
Control is based on preventive steps taken during the entire season. Once the disease has started in a field, control is very difficult, especially during wet weather.
A. Obtain seed that has been grown in regions without overhead irrigation and is certified free from the disease-causing bacteria. This is by far the most important step. Seed may be treated by washing 40 minutes with continuous agitation in 2 parts Clorox Liquid Bleach (5.25% sodium hypochlorite) plus 8 parts water (e.g. 2 pints Clorox plus 8 pints water). Use 1 gallon of this solution for each pound of seed. Prepare fresh solution for each batch of seed treated. Rinse seed in clean water immediately after removal from the Clorox solution and promptly allow to dry prior to storing or treating with other chemicals. This treatment will likely reduce seed germination. Thus before attempting to treat an entire seed lot, perform a test using 50-100 seed and check for the effect on germination.
B. Produce plants in sterilized soil or commercially prepared mixes.
C. Avoid fields that have been planted to peppers or tomatoes within one year, especially if they had bacterial spot.
D. Do not plant diseased plants. Inspect plants very carefully and reject infected lots -- including your own! Use certified plants.
E. Prevent bacterial leafspot in the plant beds:
F. In the field start spray schedule when the disease first appears. However, do not use streptomycin in the field.
A. Cercospora leafspot of pepper may resemble bacterial spot and can be serious during dry weather. The above procedures will also control this disease. For accurate diagnosis, contact your county agent to send diseased leaves to the Plant Disease and Insect Clinic, N. C. State University.
Always follow directions on the label of agricultural chemicals. Federal
and State registrations change periodically. Observe safety directions
on the label of the container, and dispose of excess material and empty
containers in a safe manner.
North Carolina Cooperative Extension Service personnel.
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of specific chemicals are based upon information on the manufacturer's
label and performance in a limited number of trials. Because environmental
conditions and methods of application by growers may vary widely, performance
of the chemical will not always conform to the safety and pest control
standards indicated by experimental data.