Bacterials spot
 Phytophthora blight
 Cercospora leaf spot
 Tobacco mosaic virus
 Tomato spotted wilt virus...

Title: Some common diseases of pepper in Florida
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066829/00001
 Material Information
Title: Some common diseases of pepper in Florida
Series Title: Plant Pathology Circular 946
Physical Description: Book
Language: English
Creator: Pernezny, Ken
Kucharek, Tom
Affiliation: University of Florida -- Florida Cooperative Extension Service -- Department of Plant Pathology -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 1999
Spatial Coverage: North America -- United States of America -- Florida
 Record Information
Bibliographic ID: UF00066829
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Bacterials spot
        Page 1
    Phytophthora blight
        Page 2
    Cercospora leaf spot
        Page 3
    Tobacco mosaic virus
        Page 4
    Tomato spotted wilt virus (TSWV)
        Page 5
        Page 6
        Page 7
        Page 8
Full Text


Some Common Diseases of Pepper in Florida

Ken Pernezny and Tom Kucharek, Respectively, Professor, Plant Pathology,
Everglades Research and Education Center, Belle Glade; and Professor, Univer-
sity of Florida, Plant Pathology Department, Gainesville, Florida. 1991; Revised
November 1999.
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean

Pepper is an important commercial veg-
etable crop in Florida. During the months of
November through May, the country is depen-
dent on Florida for its supply of fresh peppers.
Sweet bell pepper is produced in the highest
quantity; however, recent years have seen in-
creased plantings of "specialty" items such as
jalapenos and pimientos.

Production of pepper in our state is often
severely limited by one or more disease prob-
lems. This fact sheet describes the symptoms
of several commonly observed diseases and
provides recommendations for control. Since
pesticide registrations and varieties change fre-
quently, consult the Cooperative Extension Ser-
vice for current, specific pesticide recommen-

Bacterial Spot

Bacterial Spot, caused by Xanthomonas
campestris pv. vesicatoria, is the most common and
serious foliar disease problem facing Florida
pepper growers. It is especially destructive
when the weather is warm and there are fre-
quent episodes of wind-driven rain. In south-
ern Florida, we have observed the most seri-
ous outbreaks in the months of August through

All plant parts above ground are susceptible.
In leaves, the first symptoms are watersoaked

spots on the lower leaf surface. These occur
within 3-4 days of infection. In another 2-3 days,
the lesions become tan to brown, greasy spots
on the upper leaf surface. These leaf spots
sometimes are the center for a spreading yel-
lowing of leaves. The lobed or angular lesions
often are aggregated, possibly as a result of the
transport of a number of bacteria to a leaf by
one rain drop. Leaf spots may expand and coa-
lesce to form large areas of yellow and brown
tissue with a characteristic, greasy appearance
(Fig. 1). Meanwhile on the lower leaf surface,
the spots remain watersoaked and greasy, with
the development of brown areas, especially in
the lesion centers (Fig. 2). In some cases, leaf
margins become scorched, probably as a result
of invasion of hydathodes by the bacteria. In-
fected leaves often drop prematurely, even
when only moderate damage from bacterial
spot is incurred.

Lesions in fruit appear initially as small,
raised pimples that are slightly lighter green
than the normal fruit color. They enlarge and
turn brown to black and appear as raised warts
or scabs (Fig. 3). Under humid conditions, other
microbes may enter the fruit at the bacterial spot
lesions and cause massive fruit decay.

An integrated approach, which uses several tac-
tics in concert, is needed to manage this dis-
ease. Bacterial spot is most severe when night
temperatures are above 650F, but the bacteria
can be active below that temperature. While all

pepper varieties are susceptible to one or more
races of the bacterium, differences in degree of
susceptibility exist. There is some evidence that
the pathogen can be transmitted in pepper seed.
Pepper and tomato volunteers should be de-
stroyed well before the next cropping season.
Transplants should be certified as disease-free.
Overhead irrigation should be avoided when-
ever possible. Workers and farm equipment
should be kept out of fields when fields are wet.
This organism is readily spread through fields
when contact is made with wet foliage. Avoid
unnecessary use of magnesium as foliar or soil
applications. Limited control may be obtained
with copper sprays. However, the effectiveness
of copper bactericides is limited, because of the
widespread occurrence in Florida of copper
tolerance among strains of X campestris pv.

Phytophthora Blight

Phytophthora blight, caused by the fungus
Phytophthora capsici, has caused major losses the
last few years, especially in the fall crop. All
root and shoot tissue of pepper can be infected
by P. capsici. The first symptom noted, in many
cases, is a general wilting of pepper plants (Fig.
4). The wilt, however, occurs only after the de-
velopment of lesions at any point on the stem.
The stem lesions start as dark green,
watersoaked spots or streaks, that later become
dark brown (Fig. 5). Wilting is seen above le-
sions that girdle side shoots or the main stem.

Fruit infection is common. The fungus usu-
ally first grows through the fruit stalk. Fruits
are then invaded with the development of a soft,
mushy rot. The white growth of the fungus is
often evident on the surface of lesions. Fruits
eventually shrivel up but remain on the plant
for considerable periods of time.

P. capsici is a so-called water mold. Other
watermold fungi include P. infestans that causes
late blight of tomato and potato and Pythium
spp. which cause damping-off in many crops.

P. capsici forms lemon-shaped spores (sporan-
gia) among the mass of white fungal growth that
can subsequently produce many, smaller
zoospores that are motile in water. These can
be seen by growers, agents, scouts, and others
with access to a reasonably good compound
microscope. Special resting spores with thick
walls, called oospores, are formed which en-
able the fungus to survive long periods of ad-
verse conditions.

The fungus has been reported to survive in
seed as well as in soil as oospores. The lemon-
shaped spores produced by the actively grow-
ing fungus are readily spread by splashing rain.
However, unlike many water molds, they can
also be spread by the wind. P. capsici can be
active during moist conditions from 46 to 910F.
Optimum temperatures for fungal activity
range from 68-86F. Heavy rains during warm
periods favor development of this disease.

This disease is not easy to control. Use of soil
fumigation to reduce soil populations of the
pathogen helps. Plastic mulch can reduce ac-
tual contact of soil populations of the patho-
gen with plants. Plant only on well-drained soil.
Fungicides may provide some control.

Wet Rot (Choanephora Blight)

Wet rot or Choanephora blight has become
increasingly more common and more severe in
recent years. As early fall plantings of pepper
continue to increase, we may expect to see more
damage from this disease.

The causal agent is the fungus Choanephora
cucurbitarum. This fungus is ordinarily thought
of as a "weak" pathogen; it colonizes dead or
dying tissue before it actively invades living
pepper tissue. Most of the time, it seems to start
in senescing flower petals. Once established,
entire flowers are overgrown, resulting in a
brown to black mass of soft tissue. Flower
stalks, buds, and leaves may subsequently be
invaded (Fig. 6). Spore production can occur

between 77-86F. Diagnosis of wet rot in the
field is based on the appearance of a silvery
mass of fungus growth topped with a black ball
made of great numbers of spores. The growth
looks like whiskers growing out of the affected
pepper tissue. More information on the diag-
nosis and control of wet rot can be found in the
Extension Plant Pathology Fact Sheet No. 11,
Wet Rot of Vegetable Crops.

Cercospora Leaf Spot

Cercospora leaf spot, sometimes known as
frogeye leaf spot, is common in northern Florida
during the summer. It is rare in production ar-
eas south of Orlando. Symptoms may occur in
leaves, stems, petioles, and fruit stalks. How-
ever, the leaf lesions are very distinctive and
allow one to readily recognize the disease in
the field. Spots are circular to oval, with light
tan centers and dark red borders (Fig. 7). Un-
der conditions of high moisture, the fungus
Cercospora capsici may be observed growing in
the middle of the spot, especially if a good hand
lens is used. Under a microscope, one can ob-
serve many long, thin, colorless, multicelled
spores, characteristic of Cercospora fungi.

The fungus can survive in northern Florida
on crop debris. The spores are readily trans-
mitted via wind. The disease is usually most
severe during warm, wet weather.

Prompt destruction of abandoned pepper
crops and crop rotation are non-chemical meth-
ods of control. Fungicides can control the dis-

Southern Blight (White Mold)

Pepper is included in the wide host range of
the southern blight fungus, Sclerotium rolfsii. This
disease has been more of a problem in the north-
ern part of the state. The major symptom is a
rapid wilting of plants (Fig. 8). Internal and ex-
ternal lower stem tissue is infected and discol-
ored by this fungus. The disease can be defini-

tively diagnosed by finding small, mustard
seed-sized resting structures called sclerotia at
the base of stems. Sclerotia will begin as white
structures and later darken to shades of orange
to dark brown. Southern blight is favored by
high temperatures (80-95 F).
Control is achieved by crop rotation with
nonsusceptible crops such as grasses. However,
because the sclerotia are so resistant to adverse
conditions, long rotations of several years are
best. Care must be taken not to transmit sclero-
tia within or between fields on farm equipment
or shoes of workers. Sclerotia may also be trans-
mitted in runoff from rain or irrigation. Turn-
ing soil with a moldboard plow rather than
disking prior to planting is preferred. Some
control may be obtained from the use of broad-
spectrum soil fumigants. These are usually
applied when the full-bed, plastic mulch sys-
tem is used for the production of pepper. Read-
ers can see Plant Pathology fact sheet No. 4 for
more information on southern blight.

Blossom End Rot

Blossom end rot is an abiotic problem; that is, a
living microorganism does not initiate this dis-
ease. Damage is confined to the fruit. Symptoms
begin as watersoaked spots at the blossom end
or side wall of the fruit. Damaged areas expand
and become sunken, tan to brown in color, and
dry, with a papery or leathery feel. Quite com-
monly, the affected fruit areas become covered
with saprophytic fungi, which appear as black,
feltlike growth on the fruit (Fig. 9). It is impor-
tant to know that these dark-colored fungi are
not the cause of blossom end rot, but merely
colonize damaged fruit tissue. This disorder is
directly related to calcium deficiency in devel-
oping fruit. A low calcium level in fruit can be
the direct result of insufficient calcium in the
soil. It may also be an indirect result of compe-
tition from high levels of ions such as magne-
sium. Severe fluctuations in the water status of
plants (as when drought-stress occurs among
plants) accentuate calcium deficiency in fruit.
Control is based on proper calcium nutrition

of the crop and optimum irrigation scheduling.

Tobacco Mosaic Virus

Tobacco mosaic virus (TMV) is one of the
oldest known virus pathogens affecting pep-
per. TMV has not been a major problem in pep-
pers in Florida. Many strains of the virus exist,
and symptoms of the disease vary depending
on the particular strain of virus and cultivar of
pepper. TMV is active over a broad range of
temperatures, light regimes, and nutrient situ-

Symptoms of TMV infection are more or less
typical of those associated with virus infections
of a great number of crops. Leaves are mottled
and distorted (Fig. 10). Plants are often stunted.
Fruits may also be distorted in shape and show
mottling. Systemic symptoms occur in many
strain/cultivar combinations. In these cases,
plants may wilt, exhibit extensive yellowing,
and die.

TMV may be introduced into fields, in trans-
plants, in crop debris, and on hands and cloth-
ing of workers, as well as on contaminated tools
and machinery. Workers can get TMV-laden
sap from infected plants on their hands and
readily transmit the virus from plant to plant
down the row. Some tobacco products used by
workers can be a very important source of TMV.

TMV control centers on reduction of initial
inoculum. Use of clean transplants and crop
rotation are important. Cultural practices
should be designed to minimize manipulation
of plants. Workers should wash hands and tools
with a phosphatic detergent (e.g., Spic n' Span)
or milk after touching infected plants. There are
differences in resistance to TMV among pep-
per varieties.

Aphid-transmitted viruses

Pepper mottle virus (PeMoV), potato virus Y
(PVY), and tobacco etch virus (TEV) are aphid-

transmitted viruses that have caused serious
problems throughout Florida. Cucumber mo-
saic (CMV) is another aphid-transmitted virus.
It is very difficult to specifically diagnose which vi-
rus or viruses are in a plant based on field symptoms
alone. Seek assistance from county agents, who can
enlist the aid of plant disease clinic personnel in mak-
ing a firm identification.

Symptoms can be similar for all these vi-
ruses. A mosaic pattern (blends of light and
dark green to yellow areas) with distortion is
common in leaves of plants infected with
PeMoV, PVY, or TEV. The small leaves at the
top of the plant may be crinkled. Plants may be
stunted. Veins in leaves may be banded by a
darker green than the background tissue (Fig.
11). Fruit mottling, distortion, and uneven rip-
ening are not uncommon. PeMoV can cause
mild (Fig. 12) or severe distortion of fruit and
leaves. CMV-infected plants may show large
yellow ringspots and oak-leaf patterns (Fig. 13).

All these viruses are transmitted by aphids
in a "non-persistent" manner; i.e., the viruses
are not taken up into the aphid, but remain on
the outside of the insect's mouth parts. Trans-
mission or acquisition of the virus by feeding
is accomplished in seconds. Therefore, insecti-
cides provide little control. Aphids lose the
ability to effectively transmit these viruses by
one hour after acquisition. The aphids acquire
the virus by feeding on infected weed or crop
plants. Disease occurrence parallels closely the
fluctuations in aphid populations. Tradition-
ally, these viral diseases have been worse in
the cooler and drier months of the winter and
early spring when aphids abound.

Numerous tactics have been identified to help
manage these diseases. Source plants of these
viruses include abandoned pepper crops and
the weeds black nightshade and ground cherry.
They should be identified and destroyed. Alu-
minum colored mulches have been shown to
repel aphids. Repeated sprays of a light petro-
leum oil (JMS stylet oil) reduce infection by

interfering with acquisition and transmittance
of the virus by the aphids.

Resistant varieties can be used. In south-
ern Florida, earlier fall plantings tend to avoid
peak aphid flights. However, such plantings are
likely to incur more damage from bacterial spot.
Growers are encouraged to purchase or pro-
duce certified disease-free transplants.

Tomato Spotted Wilt Virus (TSWV)

TSWV is spread primarily by thrips. Me-
chanical transmission is also possible. TSWV
can kill plants or cause symptoms such as stunt-
ing, mosaics in leaves and fruit, or necrosis
(browning) (Fig. 14). TSWV has caused severe
damage in tobacco, tomato, and many other
field, vegetable, fruit, and ornamental crop spe-
cies. Considerable information about TSWV is
available in Plant Pathology Circular 914. An
intensive control program is necessary for re-
ducing this severe disease.

Figure 1. Severe blighting of upper leaf Figure 2. Greasy appearance of bacterial spot
surface associated with bacterial spot. lesions in lower leaf surface.

p 1j -

Figure 3. Scabby appearance of bacterial spot
lesions in pepper fruit.

Figure 4. Severe wilting associated with
Phytophthora blight of pepper.




Figure 5. Advanced stage of Phytophthora
blight showing extensive browning and
collapse of stems. (photo courtesy of Ken

Figure 6. Choanephora blight (wet rot) of


B ~7r

Figure 7. Cercospora leaf spot (frog eye spot).
Note the characteristic dark red border
around the light tan centers of the spots.

Figure 9.Blossom end rot of pepper fruit.
Note the dark colored secondary fungi
growing in the damaged tissue.

Figure 8. Wilted pepper plant with Southern
blight (white mold).

Figure 10. Tobacco mosaic virus (TMV)
infection in hot pepper.




Figure 11. Vein-banding symptom caused by
an aphid-transmitted virus (potato virus Y).

Figure 13. Ringspots and oakleaf pattern in
pepper infected with cucumber mosaic virus.

Figure 12. Speckled leaf mottling associated
with pepper mottle virus.

Figure 14. Leaf distortion and necrosis
(browning) caused by tomato spotted wilt


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