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Group Title: Vegetable diseases caused by phytophthora capsici in Florida
Title: Vegetable diseases caused by Phytophthora capsici in Florida
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066805/00001
 Material Information
Title: Vegetable diseases caused by Phytophthora capsici in Florida
Physical Description: 5 p. : col. ill. ; 28 cm.
Language: English
Creator: McGovern, Robert J., 1948-
Kucharek, Tom, 1939-
Mitchell, David James, 1943-
Publisher: University of Florida, Institute of Food and Agricultural Sciences
Place of Publication: Gainesville
Publication Date: c1994
Subject: Phytophthora diseases -- Florida   ( lcsh )
Fungal diseases of plants -- Florida   ( lcsh )
Vegetables -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: R.J. McGovern, T.A. Kucharek, and D.J. Mitchell.
General Note: Caption title.
General Note: "SP 159."
General Note: "May 1994."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066805
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.
Resource Identifier: aleph - 001930346
oclc - 30856161
notis - AKA6388

Table of Contents
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Full Text

Plant Pathology Fact Sheet

Vegetable Diseases Caused by Phytophthora

capsici in Florida
P.D. Roberts, R.J. McGovern, T.A. Kucharek, and D.J. Mitchell, respectively,
Assistant Professor, Southwest Florida Research and Education Center,
Immokalee, FL 34120 ; Associate Professor, Gulf Coast Research and Education
Center, Bradenton, FL 34203, Professors, Plant Pathology Department, Univer-
sity of Florida, Gainesville FL 32611. Revised 2000

Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean


Losses caused by Phytophthora capsici
have consistently occurred in pepper produc-
tion areas on the east coast of Florida for the
past two decades. The disease is a sporadic
problem in pepper, summer squash, and wa-
termelon in most other vegetable production
areas of the state, including most notably, south-
west and west central Florida. Phytophthora
capsici can cause also significant losses in egg-
plant and tomato. The pathogen has been re-
ported to cause severe epidemics in Central and
South America, Europe, Asia, and many other
states in the United States. The host range of P.
capsici is wide and, additionally includes can-
taloupe, chayote, cucumber, honeydew melon,
marigold, macadamia nut, papaya, and pump-
kin. Diseases caused by P. capsici are often re-
ferred to as Phytophthora blight.


Phytophthora capsici causes seed rot and
seedling blight in many solanaceous crops
(pepper, eggplant, tomato) and cucurbits (can-
taloupe, cucumber, summer squash, pumpkin,
watermelon), similar to those seen with damp-

ing-off fungi and other Phytophthora spp. Rot-
ting of seedlings prior to emergence (preemer-
gence damping-off) and blighting of recently
emerged seedlings (postemergence damping-
off) can occur. The roots and plant base may be
discolored and infected seedlings often fall
over. White fungal growth may cover infected
areas of blighted seedlings under moist condi-
tions. Phytophthora capsici, as well as other
Phytophthora spp., can also produce a wide va-
riety of symptoms on mature plants that vary
by host.

Roots, stems, foliage, and fruit of mature
pepper plants are susceptible. Although infec-
tion can occur at any height on stems, it is most
common at the soil line, and starts as a dark,
water-soaked area. Stem lesions become dark
brown to black and result in girdling and plant
death (Figure 1). Infected roots are dark brown
and mushy. Leaf spots are at first small, irregu-
lar to round, and water-soaked. With age, the
spots enlarge, turn a light tan, and may crack.
Infected areas may be bordered by white fun-
gal growth during wet periods. Rapid blight-
ing of new leaves and the entire emerging shoot
may take place (Figure 2).


Pepper fruit is infected through the fruit
stalk. Fruit rot appears as dark green, water-
soaked areas that become covered with a white
to gray mold (Figure 3). Infected fruit dries,
becomes shrunken, wrinkled, and brown, and
remains attached to the stem.

Although the entire plant may be sus-
ceptible, fruit rot is the primary symptom
caused by P. capsici in eggplant. It begins as a
round, dark brown area on any part of the fruit
at any stage of maturity. The initial lesion is
surrounded by a rapidly expanding light tan
region (Figure 4). White to gray fungal growth
may appear during wet, humid periods, start-
ing on the oldest part of the fruit lesion.
Phytophthora fruit rot in eggplant lacks the con-
centric patterns and dark fruiting structures
present with Phomopsis rot. Fruit rot in egg-
plant may also be caused by other Phytophthora

Phytophthora capsici can cause crown in-
fections, leaf spot, and foliar blight in tomato
transplants, which are most severe within the
first four weeks after planting in the field. Dis-
eased crowns are brown and soft and the plant
may wilt and topple over. Another common
symptom is fruit rot. Uninjured fruit of any age
may be infected. Rot is most prevalent where
fruit contacts the soil and begins as dark, wa-
ter-soaked spots. The spot rapidly expands
during warm weather and covers 50% or more
of the fruit surface with a brown, watery dis-
coloration that may assume the appearance of
concentric rings (Figure 5). At first, infected fruit
remains smooth and firm even though the dis-
coloration extends to its center. Over time and
under humid conditions infected fruit may be
covered with white fungal growth and rot en-
tirely following invasion by secondary micro-

organisms. The symptoms of fruit rot in tomato
caused by two other Phytophthora spp., P.
dreschlera and P. nicotianae, are essentially the
same. However, tomato fruit rot caused by P.
infestans (late blight) is characterized by wrin-
kling and a definite, sunken margin.

Summer Squash

Summer squash is highly susceptible to
Phytophthora foliar blight and fruit rot. Early
foliar symptoms include rapidly expanding,
irregular, water-soaked lesions in leaves. Die-
back of shoot tips, wilting, shoot rot, and plant
death quickly follow initial infection (Figure 6).
Sunken, dark, water-soaked areas appear in
infected fruit, and are rapidly covered by white
fungal growth. Given optimal warm, wet
weather, P. capsici can devastate entire squash
plantings in a matter of days.


Watermelon foliage is less susceptible
than that of summer squash to P. capsici; foliar
symptoms of Phytophthora blight in water-
melon are generally limited to water-soaked
leaf blotches, which dry and turn brown, and
dieback. However, a fatal crown rot can occur
in watermelon plants of all ages during peri-
ods of excessive soil moisture and high patho-
gen pressure. Likewise, all stages of water-
melon fruit are highly susceptible. Early symp-
toms of fruit rot include rapidly expanding, ir-
regular, brown lesions-that become round to
oval. Concentric rings within a lesion may oc-
cur. The centers of rotted areas are covered with
a grayish mold, while the outer margins of le-
sions appear brown and water-soaked (Figure
7). The entire fruit eventually decays. Initial
symptoms of bacterial fruit blotch of water-
melon are similar to those caused by P. capsici.

However, after lesions expand, the two diseases
can be easily separated because of the presence
of extensive rind cracking and absence of fun-
gal growth with bacterial fruit blotch, while
Phytophthora rot is characterized by abundant
fungal growth accompanied by little or no
Other Cucurbits

Phytophthora capsici causes rapid blight-
ing and death of chayote plants and a fruit rot
similar to that observed in watermelon. Angu-
lar, water-soaked lesions (Figure 8), as well as
a rapid fruit rot, which is covered with white
fungal growth, are produced in cucumber.
Symptoms of Phytophthora blight in canta-
loupe include leaf lesions and tip dieback of
Disease Cycle

Phytophthora capsici may survive in and
on seed and host plant debris in the soil by
means of thick-walled, sexually-produced
spores oosporess). Both mating types of the
pathogen necessary for oospore production are
present in Florida. The pathogen produces
spores of another type called zoospores that are
contained within sac-like structures called spo-
rangia. Zoospores are motile and swim to in-
vade host tissue. Plentiful surface moisture is
required for this activity. The sporangia are
spread by wind and water through the air and
are carried with water movement in soil.
Phytophthora capsici is also moved as hyphae
(microscopic fungal strands) in infected trans-
plants and through contaminated soil and
equipment. Since water is integral to the dis-
persal and infection ofP. capsici, maximum dis-
ease occurs during wet weather and in low or
waterlogged parts of fields. Excessive rainfall,
such as that which occurs during "El Nifo"
years, coupled with standing water creates
ideal conditions for epidemics caused by P.
capsici. Growth of this pathogen can occur be-
tween 7-37C (46-99F), but temperatures be-
tween 27-32C (80-90F) are optimal for produc-
ing zoospores and the infection process. Un-

der ideal conditions, the disease can progress
very rapidly and symptoms can occur 3-4 days
after infection. Therefore, P. capsici can rapidly
affect entire fields.


Management practices in transplant pro-
duction areas include the use of pathogen-free
and fungicide-treated seed, and sterile potting
media. Transplant trays, benches, seeding
equipment and plant house benches and other
structures should be disinfested using a so-
dium hypochlorite solution or other disinfes-
tant. Steam sterilization of transplant trays may
be useful. Transplant trays with infected plants
should be removed immediately from produc-
tion sites. Workers should disinfest their hands
after contact with infected plants before resum-
ing their duties.
Planting sites should be well drained
and free of low-lying areas. Optimal water
management is essential to prevent the occur-
rence of flooded field conditions that favor
Phytophthora blight. The drainage area of the
field should be kept free of weeds and volun-
teer crop plants, particularly those in the
solanaceous and cucurbitaceous groups. A
preplant fumigant should be used. Equip-
ment should be decontaminated before mov-
ing between infested and noninfested fields.
Infected fruit should be culled to prevent
spread in the packinghouse and during
shipment. Effective, labeled fungicides
should be used preventively according to
label instructions. It is essential that fungi-
cides with different modes of action be ro-
tated to prevent the buildup of fungicide
resistance in P. capsici; rotating or tank-mixing
a systemic with a contact fungicide is a good
rule of thumb. Contact your county extension
agent for currently labeled fungicides. Resis-
tance to this disease has not been identified in
cultivars currently grown in Florida.







Figure 1. Stem lesions at the soil line and
root rot caused by Phytophthora capsici in

Figure 2. Foliar blight of pepper caused by
Phytophthora capsici.

Figure 3. Fruit rot in pepper caused by Figure 4. Fruit rot in eggplant caused by
Phytophthora capsici. Phytophthora capsici.

, ii


Figure 5. Fruit rot in tomato caused by
Phytophthora capsici.

Figure 7. Various stages of fruit rot of water-
melon caused by Phytophthora capsici. Left,
early symptoms; right advanced symptoms.

Figure 6. Foliar blight and fruit rot of yellow
summer squash caused by Phytophthora

Figure 8. Foliar lesions caused by
Phytophthora capsici in cucumber.


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