BACTERIAL SPOT OF PEPPER AND TOMATO
W. C. Nesmith and John R. Hartman
Bacterial spot can result in severe
damage to sweet pepper, tomato or pimento crops to the extent that it is
a limiting factor to successful production. The bacterium (Xanthomonas
vesicatoria) attacks leaves, fruits and stems causing blemishes on
these plant parts. Outbreaks of leaf spotting have resulted in leaf drop
and poor fruit set in the field. The defoliation from leaf spotting can
increase the incidence of sun scald on the fruit. Badly spotted fruit is
of little value. Injury from this disease allows secondary fruit rotting
organisms to get into the fruits, causing further damage.
Leaves-- Spots begin as small,
dark, water-soaked areas which become dark brown and slightly raised on
the leaf underside. The spots often enlarge, and may be either dark colored
or have tan colored centers with dark margins. The size and shape of leaf
spots may vary under different conditions. Leaves with too many spots promptly
turn yellow and drop, defoliating the plants.
Fruits-- Fruit blemishes begin
as small, water-soaked spots which enlarge, becoming blister-like, rough
and warty. The spots are brown and seldom exceed 1/4 inch in diameter.
Often the disease extends into the seed cavity.
The source of first infection is usually
contaminated seed or transplants or carry-over in infested plant debris
in the field. The disease is favored by warm, wet, rainy weather, and its
spread is aided by driving rain and wind-blown debris and soil which cause
mechanical injury to the leaves and fruits. During such weather the pathogen
can colonize the leaf surfaces, than the bacteria enters through these
and other wounds or through leaf stomates and spread from plant to plant
by splashing rain.
1.Use certified, disease-free transplants.
Nearby transplant sources pose less disease risk than distant sources.
Groups of growers should diversify sources of transplants to reduce disease
2.Use commercially produced, disease-free
seed. If seed has not already been treated, use bacterial seed treatment
prior to planting. Contact your county Extension office for current recommendations.
3.Rotate peppers or tomatoes with nonrelated
crops from one year to another. Fields should be free of peppers or tomatoes
2 years before repeat cropping. Control weeds during rotation. Fescue sod
is an excellent rotational crop.
4.Spray plants as needed with approved
bactericides to slow down the spread of disease. Sprays need to be applied
weekly or more often during rainy periods. Use of high pressure hydraulic
or air blast sprayers is essential. Contact your county Extension office
for the current spray recommendations.
5.Do not work plants while they are