Title: Florida plant disease management guide
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 Material Information
Title: Florida plant disease management guide
Alternate Title: Ornamentals and turf
Fruit and vegetables
General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques
Physical Description: v. : ; 28 cm.
Language: English
Creator: University of Florida -- Dept. of Plant Pathology
Florida Cooperative Extension Service
Publisher: The Extension
Place of Publication: Gainesville Fla
Frequency: annual
regular
 Subjects
Subject: Plant diseases -- Periodicals -- Florida   ( lcsh )
Pesticides -- Periodicals   ( lcsh )
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Statement of Responsibility: Plant Pathology Dept., University of Florida and Institute of Food and Agricultural Sciences, Florida Cooperative Extension, University of Florida.
Numbering Peculiarities: Issued in three volumes: v. 1, General plant pathology, field crops and pasture grasses, fungicides, adjuvants and application techniques; v. 2, Ornamentals and turf; v. 3, Fruit and vegetables.
General Note: Description based on: 1999-2000.
General Note: "SP-52"
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Bibliographic ID: UF00053871
Volume ID: VID00022
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 44549741
lccn - 00229071
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Preceded by: Florida plant disease control guide

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PDMG-V3-50
UF UNIVERSITY of

UFLORIDA
IFAS Extension



2006 Florida Plant Disease Management Guide:

StrawberryI


Natalia A. Peres2


Alternaria Rot

Alternaria rot, caused by Alternaria tenuissima,
occurs infrequently and is usually not important in
most strawberry growing regions.

This rot affects ripe fruit in the field as well as
post harvest. Lesions are irregular in shape and
slightly sunken. Older lesions are circular, firm,
sunken, and dark green to black due to sporulation of
the fungus (Figure 1).

Management

Cultural: Do not leave over-ripe fruit in the field.

Angular Leaf Spot

Angular Leaf Spot (ALS), caused by
Xanthomonasfragariae, is an important disease on
winter strawberry production worldwide. The disease
was first reported in Minnesota in 1960 and since then
it has been found in almost all cultivated strawberry
areas in the U.S.


Figure 1. Alternaria Rot.

Symptoms

The first symptoms ofALS begin as small,
water-soaked lesions on the undersurface of the
leaves (Figure 2). When moisture is high on the


1. This document is PDMG-V3-50, of a series of the Department of Plant Pathology, 2006 Florida Plant Disease Management Guide; Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised July 2006. Please visit the EDIS Web site at
http://edis.ifas.ufl.edu.
2. N. A. Peres, assistant professor, Plant Pathology Department, Gulf Coast Research and Education Center, Wimauma, FL; Florida Cooperative Extension
Service, Insitute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the
products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and
other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,
sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,
University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry
Arrington, Dean






2006 Florida Plant Disease Management Guide: Strawberry 2


leaves, these lesions ooze sticky droplets of bacteria.
As the disease develops, the lesions enlarge to form
reddish-brown spots that later become necrotic. A
practical way to recognize the disease is to place the
leaves against a source of background light where the
spots are seen as translucent. The tissue with older
lesions eventually dies and dries up giving leaves a
ragged appearance. If the disease invades the
vascular system of the plant, the disease will be
difficult to control and affected plants may wilt and
die.

















Figure 2. Angular Leaf Spot (ALS).

Causal organism

X fragariae is a slow-growing, gram-negative,
motile bacterium that is highly specific to wild and
cultivated strawberry.

Disease cycle and epidemiology

The primary source ofinoculum in a new field is
contaminated transplants. Secondary inoculum comes
from bacteria that exude from lesions under high
moisture conditions. Bacteria can survive on dry
infested leaves and tissue buried in the soil for up to 1
year. The pathogen can be spread easily by harvesting
operations when wet and cool conditions favor the
production of bacterial exudate. The pathogen also
can be dispersed by rain and overhead sprinkler
irrigation. Little is known regarding the epidemiology
of ALS; however, development of the disease is
favored by cool days (200C/680F) and cold nights
(2-40C/36-390F).


Management

Cultural: The best way to control ALS is to use
pathogen-free transplants. Harvesting and moving
equipment through infected fields should be avoided
when plants are wet. Minimizing the use of overhead
sprinklers during plant establishment and for freeze
protection may also reduce the spread and severity of
the disease.

Chemical: See Table 1.

Anthracnose Fruit Rot

Anthracnose fruit rot, caused by Colletotrichum
acutatum, is an important disease for strawberry
production worldwide. Although fruit rot is the most
important symptom caused by C. acutatum, the
fungus can also attack other parts of the plant
including the crown, leaves, petioles, and roots.

Symptoms

Symptoms of anthracnose fruit rot appear as
dark, sunken lesions on infected fruit. On green fruit,
anthracnose lesions are small (1/16 to 1/8-inch
across) hard, sunken, dark brown or black.Lesions on
ripening fruit are larger (1/8 to 1/2 inch) hard,
sunken, and tan to dark brown (Figure 3). During wet
weather, the lesions become covered by sticky, light
orange ooze composed of millions of spores
conidiaa) in a mucilaginous matrix. When conditions
are favorable for infection, multiple lesions nearly
cover the fruit and lesions may appear on petioles.
Strawberry flowers are highly susceptible and
blighted flowers turn brown and remain attached to
the plant, a symptom also produced by the fungus
Botrytis cinerea.

Causal organism

C. acutatum produces orange masses of conidia
that are hyaline, straight and usually with pointed
ends. Molecular analysis of C. acutatum revealed that
the population on strawberry reproduces asexually
and has limited diversity. Other species of
Colletotrichum, such as C. fragarie and
C.gloeosporioides, cause anthracnose diseases of
strawberry but are less frequently involved in fruit rot.






2006 Florida Plant Disease Management Guide: Strawberry 3


Figure 3. Anthracnose Fruit Rot.

Disease cycle and epidemiology


Infected transplants are a common source of
inoculum for production fields. C. acutatum
apparently spreads first on the foliage, often without
causing visible symptoms. Some conidia are formed
on green leaves and petioles, and more are produced
as the tissue ages and dies. Conidia are moved from
the foliage to flowers and fruit by splashing water and
harvesting operations. There, they germinate and
infect tissues. As anthracnose lesions develop,
abundant spores are formed that may be moved to
other plants and new fields on equipment and
harvesters. Warm wet weather favors infection and
disease spread.

Management

Cultural: Transplants should be obtained from
pathogen-free nurseries. Moving personnel and
equipment from diseased fields into healthy fields
should be avoided without proper cleaning and
disinfection. Carmine and Sweet Charlie cultivars are
considered relatively resistant to anthracnose fruit rot.
Strawberry Festival is moderately susceptible and
Camarosa and Treasure are highly susceptible.

Chemical: See Table 1.

Botrytis Fruit Rot or Gray Mold

Botrytis fruit rot, also known as gray mold,
caused by Botrytis cinerea, is one of the most
important diseases of strawberry worldwide. B.
cinerea is a cosmopolitan fungus that infects a wide
range of fruit, vegetable, and weed species.


Symptoms

Botrytis fruit rot occurs in the field and after
harvest. Infection occurs in the flowers and recently
set fruitlets, but the symptoms are commonly
observed on green and ripening fruit. Lesions begin
as small, light brown spots that quickly enlarge and
become covered with white fungal mycelia. Under
moist conditions, gray to brown spores cover the
lesions and the entire fruit may become mummified
(Figure 4). When diseased fruit are disturbed, large
numbers of spores are often released and are visible
as gray puffs.






Figure 4. Botrytis Fruit Rot...















Figure 4. Botrytis Fruit Rot.


Causal organism


The pathogen produces hyaline, septate hyphae.
Single-celled, multinucleated, ellipsoid conidia are
produced on conidiophores. Conidia are hyaline
individually but appear gray in mass.

Disease cycle and epidemiology

B. cinerea is a common colonizer of strawberry
foliage in the nursery, and is also present on dying
vegetation around strawberry fields. After runner
transplants are planted, spores produced on old dying
leaves rapidly colonize new emerging leaves without
causing visible symptoms. These spores conidiaa) are
dispersed by air, water, and harvesters to infect
flowers during the main bloom period in January and






2006 Florida Plant Disease Management Guide: Strawberry 4


February. Cool to mild temperatures and prolonged
leaf wetness promote spore production, germination,
and infection of stamens, petals, and other floral
parts. Flower infections often progress slowly, with
lesions becoming visible on green and ripening fruit 2
to 4 weeks after infection. Direct infection of fruit by
spores is not considered important in the field or after
harvest. However, the pathogen also spreads from
diseased fruit to healthy fruit by direct contact. As the
epidemic progresses, diseased fruit, mummified fruit,
and decayed flowers and pedicles become important
new sources of inoculum. Botrytis fruit rot is
especially damaging in annual production systems
with prolonged flowering and fruiting cycles. The
disease is favored by cool and wet weather. In
Florida, the second crop of fruit that ripen in
February and March are more seriously affected than
the first crop of fruit that ripen in December-January.

Management

Cultural: Removal of infected fruit and plant
debris can be used to reduce inoculum, but is not
practical for control of Botrytis fruit rot. Cultivars
Camarosa, Carmine and Treasure are less susceptible
than Strawberry Festival and Sweet Charlie.

Chemical: Fungicides should be applied at peak
bloom.

See Table 1.

Colletotrichum Crown Rot

Colletotrichum crown rot, caused by
Colletotrichum gloeosporioides or C. fragariae, is a
serious disease in subtropical production regions.
Although crown rot is observed in fields during the
winter production season, it is most severe in
nurseries in the southeastern United States and is one
of the primary reasons that production of transplants
for the Florida production season has been moved to
higher latitudes.

Symptoms

Symptoms caused by C. gloeosporioides and C.
fragariae are virtually indistinguishable in the field.
Plants infected initially show signs of water stress
and may collapse relatively rapidly (2-3 days) under
high temperatures. Under cool temperatures, it may


take weeks before plants collapse. The internal
crowns of infected plants show a reddish-brown and
firm rot when cut (Figure 5). Typically there are no
lesions on foliage or stolons and symptoms may be
confused with those of Phytophthora crown rot.

10 *.


Figure 5. Colletotrichum Crown Rot.

Causal organism


Conidia of C. gloeosporioides are barrel shaped
with both ends rounded, whereas conidia of C.
fragariae are narrower at one end and have a slightly
pointed morphology. Setae of C. fragariae differ
from those of C. gloeosporioides in that they function
as phialides and conidia can often be observed at the
ends.

Disease cycle and epidemiology

Propagation of plants in Canada and northern
states for the Florida production season has greatly
reduced the incidence of crown rot. However, during
the warm months at the beginning and end of the
production season crown rot incidences up to 5% do
occur on plants in Florida fields. Recent studies have
shown that inoculum for crown rot infections in
Florida may be coming from non-cultivated hosts.
Colletotrichum sp. responsible for crown rot do not
appear to survive between seasons in subtropical
production systems on plant debris since plants are
usually killed immediately after the production
season ends in the spring and the fungus disappears
from crowns during the hot summer months.






2006 Florida Plant Disease Management Guide: Strawberry 5


Chemical: See Table 1.


Management


Leaf Spot


Cultural: Transplants from northern nurseries
should be used for controlling crown rot. Reducing
water on foliage by using drip irrigation will also
limit dispersal of the pathogen. Treasure cultivar is
considered highly resistant to crown rot. Sweet
Charlie, Carmine and Camino Real have moderate
levels of resistance and Festival and Camarosa are
highly susceptible.

Chemical: See Table 1.

Leaf Scorch

Leaf scorch, caused by Diplocarpon earlianum,
is a common leaf disease of strawberries grown
worldwide.


Symptoms


Symptoms on leaves are numerous irregularly
shaped purplish blotches that are 1/16 to 3/16 inch in
diameter. Clusters of the blotches turn brownish, but
never white or gray as in the case of common leaf
spot. Dark, glistening acervuli appear in the lesions
on the upper surfaces of the leaves. In severe cases,
the leaf margins curl upward and the leaves dry to a
tan color, progressing from the margins to the midrib,
giving the leaf a scorched appearance.

Causal organism

The fungus is limited to species and cultivars of
Fragaria although physiological and pathogenic
specialization among isolates has been reported.

Disease cycle and epidemiology

Leaf scorch is favored by long periods of leaf
wetness (12 h or more), frequent rain, and moderate
temperatures (60-780F). The severity of the disease
is usually low in annual production systems.

Management

Cultural: Prolonged use of overhead irrigation
should be avoided.


Leaf spot, caused by Mycosphaerellafragariae,
is one of the most common diseases of strawberries
worldwide.

Symptoms

Leaf lesions are initially small, purplish-red and
less than 1/8 inch in diameter. The spots may enlarge
to 1/4 inch depending on the cultivar. On some, the
lesions remain very small and numerous and the
leaflets appear "rusty." On others, the lesions increase
in size to 1/4 inch or larger and develop white or gray
centers with reddish-purple to dark purple borders.
Lesions may also form on fruit, calyxes, petioles, and
stolons. Severe infection can result in death of
leaflets and defoliation of plants.


Causal organism


The fungus is considered to be pathogenic only
to species and cultivars of Fragariae although several
races have been defined according to their effects on
different cultivars.

Disease cycle and epidemiology

Older lesions provide inoculum to infect plants
during the season. Conidia are produced during the
entire season if weather conditions are favorable
(50-860F) and are splash disseminated by water.

Management

Cultural: Resistant cultivars and disease-free
transplants should be used.

Chemical: See Table 1.

Charcoal Rot

Charcoal rot, caused by Macrophomina
phaseolina, was first reported in Florida in 2005.

Symptoms

Infected plants wilt, are stunted, and eventually
die. The disease affects the plant roots and crown, and
it can be difficult to distinguish from other crown






2006 Florida Plant Disease Management Guide: Strawberry 6


diseases. Isolation in laboratory is necessary for
proper identification.

Causal organism

Macrophomina phaseolina produces numerous
dark oblong sclerotia on the isolation medium after 4
to 5 days incubation. Ostiolate pycnidia bearing
relatively large, broadly ellipsoidal, hyaline conidia
occasionally developed on host tissue after 8 to 10
days of incubation.

Management

Cultural: Planting should be avoided in fields
with history of Macrophomina diseases of other
crops.

Phomopsis Leaf Blight and
Phomopsis Soft Rot (Phomopsis
obscurans)

Phomopsis leaf blight and Phomopsis soft rot,
caused by Phomopsis obscurans, can occasionally
cause serious problems on strawberry, especially on
plants propagated in nurseries from the southeastern
United States.

Symptoms

Lesions in the foliage are initially small and
circular reddish-purple spots. Older spots can
coalesce and form large V-shaped lesions with the
widest part of the lesions at the leaf margin and the
narrow base centered on a vein (Figure 6). Black
specks of pycnidia often develop within the central
areas of the older lesions. Initial symptoms on fruit
are round, light pink, and water-soaked lesions
(Figure 7). Frequently, two or more lesions may
coalesce into large soft brown lesions with dark
fruiting structures (pycnidia) on the surface. The
disease may also produce dark, sunken, and
elongated lesions in stolons and petioles that are very
similar in appearance to anthracnose.

Disease cycle and epidemiology

Conidia of Phomopsis obscurans are spread by
splashing water, harvesting operations, and
equipment. The disease is favored by warm, wet
conditions and can be the most severe during the


Figure 6. Phomopsis Leaf Blight.


Figure 7. Phomopsis Soft Rot.

summer on plants propagated in Florida and the
southeastern United States. In fruit production fields
in Florida, Phomopsis leaf blight will develop during
the fall and early winter. The fruit rot phase of the
disease typically develops in the fall in fields where
leaf blight is present, then disappears as the winter
weather gets colder and drier. Both the leaf blight and
fruit rot caused by P. obscurans are rarely observed
later in the season.






2006 Florida Plant Disease Management Guide: Strawberry 7


Management

Cultural: Transplants should be obtained from
northern Canada or the western United States since
leaf blight typically occurs on transplants propagated
in the southeastern United States.

Chemical: See Table 1.

Phytophthora Crown Rot

Phytophthora crown rot, caused by Phytophthora
cactorum and P. citricola, can be a serious disease of
annual production strawberry in central Florida.

Symptoms

The disease is characterized by a sudden decline
and wilt of plants. Reddish-brown coloration on the
internal crown makes symptoms difficult to
distinguish from those produced by Colletotrichum
gloeosporioides or C. fragariae. Thus, isolation and
characterization of the pathogen is important for
proper identification.

Causal organism

In Florida, Phytophthora cactorum has
historically been responsible for causing the disease,
although P. citricola has been the primary cause of
Phytophthora crown rot in recent years.

Disease cycle and epidemiology

Infected transplants are the primary source of
inoculum for epidemics in Florida. The pathogen
produces zoospores that infect strawberry plants
under wet conditions. Phytophthora species produce
oospores that may persist in infested soil and plant
debris, although oospores have not been observed in
Florida. Phytophthora cactorum also causes leather
rot and the infected fruit may provide a source on
inoculum. The disease is favored by warm
temperatures and prolonged periods of wetness,
conditions that are common during the plant
establishment period (October) in Florida.

Management


Cultural: Use of disease-free transplants is the
best way to control the disease.

Chemical: See Table 1.

Phytoplasma Diseases

Several diseases of strawberry are caused by
phytoplasmas. Some of the most common are aster
yellows, green petal, bronze leaf wilt, and multiplier.

Symptoms

Phytoplasma diseases can be recognized by one
or more characteristic symptoms, such as phyllody
(Figure 8), stunting, and yellowing. Molecular
techniques are necessary for detection and
identification of phytoplasmas.

The disease is transmitted by grafting and by
leafhoppers.


Figure 8. Phytoplasma-green petal.

Management


Cultural: Use of disease-free transplants.

Powdery Mildew

Powdery mildew, caused by Sphaerotheca
macularis, occurs in most areas of the world where
strawberries are grown. The disease is particularly
severe on strawberries grown in greenhouses or
plastic tunnels. In open fields in central Florida, the
disease is typically most severe in November and
December and it may reappear in late February and
March.






2006 Florida Plant Disease Management Guide: Strawberry 8


Symptoms

Early symptoms appear as small white patches of
fungus growing on the lower leaf surface. These
patches can expand and coalesce to cover the entire
leaf surface under favorable conditions. In some
cultivars, irregularly shaped yellow or reddish brown
spots will develop on colonized areas on the lower
surface of the leaf and eventually appear on the upper
surfaces. The edges of heavily infected leaflets curl
upward (Figure 9). The fungus can also infect fruit
and may reduce fruit quality and marketable yields.





















Figure 9. Powdery Mildew.

Causal organism

Sphaerotheca macularis is an obligate parasite
that only infects living tissue of wild or cultivated
strawberry. The fungus produces chains of dry,
hyaline conidia and, occasionally, cleistothecia
containing ascospores on infected leaves.

Disease cycle and epidemiology

The fungus readily infects living, green leaves in
the nursery. Thus, infected transplants are normally
the primary source of inoculum for fruiting fields in
Florida. When conditions are favorable, conidia
produced on infected plants are wind dispersed.
Development and spread of powdery mildew is


favored by moderate to high humidity and
temperatures between 600 to 800 F. Rain, dew and
overhead irrigation inhibit the fungus. Because dry
conditions and high humidity are common in
greenhouses and plastic tunnels, powdery mildew is
typically more severe in protected culture.

Management

Cultural: Disease-free transplants should be used
for controlling powdery mildew, although fields can
become infected by conidia blown in from
neighboring fields. Cultivars differ widely in their
resistance to powdery mildew. Unfortunately, some
of the most popular cultivars in Florida, Strawberry
Festival, Camarosa, and Winter Dawn, are quite
susceptible to the disease.

Chemical: See Table 1.

Rhizopus Rot or Leak

Rhizopus rot or leak, caused by Rhizopus
stolonifer, affects fruit and is most serious after
harvest or in storage but can also occur in the field.

Symptoms

Infected fruits collapse and rapidly leak juice
(Figure 10). A loose, cottony growth of mycelium
(whiskers) grows over the surface of the fruit.
Fruiting bodies (sporangia) appear as black dots
scattered throughout the mycelium.

Causal organism

Rhizopus spp. cause rots of various fruit and
vegetable crops and physiological specialization has
not been established.

Disease cycle and epidemiology

The fungus survives on crop debris and in the
soil between seasons. Rhizopus can only infect
through wounds. Under favorable conditions of high
temperature and moisture, sporulation is rapid and
abundant. Spores are disseminated by air and by
insects.

Management







2006 Florida Plant Disease Management Guide: Strawberry 9


Figure 10. Rhizopus rot or leak.


Cultural: Fruit should be handled carefully to
avoid bruising. When possible, fruit should be picked
during the morning, protected from the sun, and
cooled rapidly before shipping.

Root Necrosis

Root necrosis, caused by Colletotrichum
acutatum, has been observed in Florida since 2000.
This fungus is widely known as a fruit rot pathogen,
but also infects other strawberry tissues, including the
roots.

Symptoms

Transplants with infected root systems often
grow poorly or fail to become established after
overhead irrigation is withdrawn. Few functional
roots are found on infected plants even 1 to 2 weeks
after transplant. Old structural roots are brown or
black with few feeder roots, whereas new roots
develop brown lesions, die back from the tip, or fail
to emerge from the crown. In severe cases, C.
acutatum enters the crown, causing a basal crown rot
and eventually killing the plant. Plants in affected
fields are stunted or irregular in size, flower late, and
produce a poor early crop (Figure 11). Infected plants
may recover during the cool winter months and
produce normally in February and March, if an
outbreak of anthracnose fruit rot does not follow.


Figure 11. Root Necrosis.



Causal organism

See anthracnose fruit rot.


Disease cycle and epidemiology

C. acutatum frequently colonizes leaves and
petioles of runner plants in the nursery. Obvious
symptoms may not be visible in the nursery
environment, but if inoculum is allowed to build up
and the weather is favorable, lesions may develop on
the petioles. Little is known about how or when the
pathogen spreads from colonized tissue above the
ground to the root system below. However, C.
acutatum grows freely in diseased tissues, and has
been isolated from the soil around diseased plants.
Healthy plants are presumably contaminated by this
inoculum during normal digging, trimming, and
packing operations in the nursery. Cultivars that are
highly susceptible to anthracnose fruit rot, e.g.,
Camarosa and Treasure, are susceptible to root
necrosis disease as well. Early in the season,
plant-to-plant disease spread is not thought to occur
below ground as the root systems are relatively
isolated. However, above-ground spread does occur
and may be facilitated by overhead irrigation during
establishment.






2006 Florida Plant Disease Management Guide: Strawberry 10


Disease cycle and epidemiology


Management

Cultural: Disease-free transplants should be used.

Chemical: A pre-plant fungicide dip may
suppress disease development when the disease is
confirmed or when susceptible cultivars are being
grown. See Table 1.

Stem-End Rot and Leaf Blotch

Stem-end rot and leaf blotch, caused by
Gnomonia comari, occurs sporadically and may be
found in association with Phomopsis obscurans.

Symptoms

Fruits can be affected at all stages. Characteristic
symptoms on small fruits are irregular brown areas on
the surface and cessation of fruit development. On
ripe fruits, the disease is characterized by a soft rot
that is often invaded by secondary organisms. Leaf
blotch lesions on young leaves are purple to brown
and occasionally enlarge to form light brown necrotic
spots on older leaves (Figure 12). The outer leaves
may die resembling the symptoms of Verticillium
wilt. Peduncles, petioles, and calyxes may also be
affected.


Fruit is infected by conidia and ascospores
produced on other parts of the plant or other hosts.
The disease is spread by frequent rains or overhead
irrigation. The fungus generally penetrates through
stomata or wounds when humidity is high.

Management

Cultural: Some strawberry cultivars may be
resistant but there is no information regarding
susceptibility of cultivars grown in Florida.

Chemical: See Table 1.

Verticillium Wilt

Verticillium wilt, caused by Verticillium
albo-atrum and V dahliae, is an occasional problem
in winter annual strawberry production. These
pathogens have wide host ranges and isolates that are
pathogenic on potato and tomato are also pathogenic
on strawberry.

Symptoms

Initial symptoms are wilting of the plant and
browning of the margins and interveins of older
leaves. Younger leaves may remain green, but
develop slowly and the plant becomes stunted,
declines and ultimately dies (Figure 13). The crown
of diseased plants develops necrotic streaking that
appears similar to other crown rots. It is necessary to
isolate the fungus to confirm its identity.


Figure 12. Leaf Blotch.

Causal organism


G. comari infects numerous rosaceous species
worldwide. Perithecia are globose and beaked, and
ascospores are hyaline, straight or slightly curved,
and septate.


Figure 13. Verticillium Wilt.






2006 Florida Plant Disease Management Guide: Strawberry 11


Disease cycle and epidemiology

Infected transplants appear to be the primary
source of inoculum for outbreaks of Verticillium
crown rot in Florida. Disease spread from plant to
plant seems unlikely, but infection may occur through
root contact. The pathogen is favored by sudden
weather changes such as increases in temperatures or
lack of moisture.

Management

Cultural: The best method to control Verticillium
wilt is to use disease-free transplants. Strawberry
nurseries should avoid areas that were previously
used for potato or tomato production. This fungus is
likely to be more severe at high pHs, so care should
be taken to not over lime the soil.





2006 Florida Plant Disease Management Guide: Strawberry 12


Table 1. Fungicides approved for disease management of strawberry in Florida.


Chemical Fungicide Maximum Rate/ Acre/ Min. Days Pertinent Diseases or Remarks
Group a Applic. Season to Harvest Pathogents

Abound 11 15.4 fl. oz. 1.92 qt. 0 Anthracnose Do not make more than 2
(azoxystrobin) Powdery mildew sequential applications and no
Botrytis (suppression only) more than 4 applications per crop
year. See label for instructions on
dipping transplants
Aliette WDG 33 5 Ib. 30 Ib. 12 hr Phytophthora diseases Do not tank mix with copper
(fosetyl-AI) ___ fungicides
Cabrio EG 11 14 fl. oz. 70 fl. oz. 0 Anthracnose Do not make more than 2
(pyraclostrobin) Leaf spot sequential applications and no
Powdery mildew more than 5 applications per crop
Botrytis (suppression only) year
Captan 50 WP M3 6 Ib. 48 Ib. 1 Anthracnose Rate per treated acre. Special label
captain ) Botrytis fruit rot for FL allows up to 24 applications
Leaf spot per season
Captan 80 WDG M3 3.75 Ib. 30 Ib. 1 Anthracnose Rate per treated acre. Special label
captain ) Botrytis fruit rot for FL allows up to 24 applications
Leaf spot per season
Captec 4L M3 3 qt. 24 qt. Anthracnose Rate per treated acre. Special label
captain ) Botrytis fruit rot for FL allows up to 24 applications
Leaf spot per season
Captevate 68 WDG M3 + 17 5.25 Ib. 21 Ib. 0 Botrytis fruit rot Do not make more than 2
captainn + fenhexamid)_____ Anthracnose consecutive applications
Copper M1 or M9 varies varies 1-2 Angular leaf spot Frequent use of copper fungicides
(many brands)1 __ may cause foliar burn
Elevate 50 WDG 17 1.5 Ib. 6 Ib. 0 Botrytis fruit rot Do not make more than 2
(fenhexamid)______ consecutive applications
Nova 40W 3 5 oz. 30 oz. 0 Powdery mildew Do not plant rotational crops until
(myclobutanil) Leaf spot 30 days after last application
Leaf blight
Potassium bicarbonate varies varies 1 Powdery mildew Do not mix with highly acid
(many brands)2 products
Potassium phosphite varies varies 0 Phytophthora diseases May cause foliar burn if applied
(many brands)3______ with copper based products





2006 Florida Plant Disease Management Guide: Strawberry 13


Table 1. Fungicides approved for disease management of strawberry in Florida.


Chemical Fungicide Maximum Rate/ Acre/ Min. Days Pertinent Diseases or Remarks
Group a Applic. Season to Harvest Pathogents

Pristine 11 + 7 23 oz. 115 oz. 0 Botrytis fruit rot Do not make more than 2
(pyraclostrobin + Anthracnose consecutive applications and no
boscalid) Powdery mildew more than 5 applications per crop
Leaf spot
Procure 50WS 3 8 oz. 32 oz. 1 Powdery mildew Do not plant leafy vegetables
(triflumizole) within 30 days or root vegetables
within 60 days or rotational crops
not on label for one year after
application
Ridomil Gold EC 4 1 1 1/2 Phytophthora diseases See label for use in drip irrigation
(metalaxyl-M) pt/ qts/trtd
trtd.acre acre
Rovral 4 2 2 pt. 2 pt. N/A Botrytis fruit rot Do not make more than 1
(iprodione) Stem end rot application per season. Do not
Phomopsis soft rot apply after bloom initiation
Leaf spot
Rovral 75 WG 2 1.33 1.33 N/A Botrytis fruit rot Do not make more than 1
(iprodione) Stem end rot application per season. Do not
Phomopsis soft rot apply after bloom initiation
Leaf spot
Scala SC 9 18 fl. oz. 54 fl. oz. 1 Botrytis fruit rot Do not make more than 2
(pyrimethanil) consecutive applications. Do not
use more than 2 of 6 applications
in any one season.
Serenade Max 3 Ib. 0 Powdery mildew Should be used in combination
(Bacillus subtilis) Botrytis fruit rot with other fungicides
Anthracnose
Sulfur M1 or M9 varies varies 1 Powdery mildew Do not use during hot weather
(many brands)4
Switch 62.5 WG 9+ 12 14 oz. 56 oz. 0 Botrytis fruit rot Do not make more than 2
(cyprodinil + fludioxonil) Anthracnose consecutive applications. Do not
plant crops not on the label for 30
days after last application





2006 Florida Plant Disease Management Guide: Strawberry 14


Table 1. Fungicides approved for disease management of strawberry in Florida.


Chemical Fungicide Maximum Rate/ Acre/ Min. Days Pertinent Diseases or Remarks
Group a Applic. Season to Harvest Pathogents

Thiram 65 WSB M2 5 Ib. 25 Ib. 3 Botrytis fruit rot Do not rotate treated crops with
(thiram) other crops for which Thiram is not
registered
Topsin 4.5 L 1 20 fl. oz. 80 fl. oz 1 Botrytis fruit rot Do not use Topsin alone.
(thiophanate-methyl) Colletotrichum crown rot Fungicides from different chemical
Leaf scorch groups should be used in spray
Leaf blight program for disease resistance
Powdery mildew management
Topsin M 70 W, 1 1 Ib. 4 Ib. 1 Botrytis fruit rot Do not use Topsin alone.
Topsin M WSB Colletotrichum crown rot Fungicides from different chemical
(thiophanate-methyl) Leaf scorch groups should be used in spray
Leaf blight program for disease resistance
Powdery mildew management
N/A Not available
1 e.g. Kocide, Champion, Champ, Basicop, Cuprofix Disperss, Copper Count-N, Nordox, Nu Cop
2 e.g. Kaligreen, Armicarb, Milstop
3 e.g. Fosphite, Helena Prophyt
4e.g. Micro Sulf, Enduro, Sulfur 90W, Super-Six, Microthiol Disperss, Wettable Sulfur, Kumulus
a Fungicide group (FRAC Code): Numbers (1-37) and letters (M, U, P) are used to distinguish the fungicide mode of action groups. All fungicides within the
same group (with same number or letter) indicate same active ingredient or similar mode of action. This information must be considered for the fungicide
resistance management decisions. M = Multi site inhibitors, fungicide resistance risk is low; U = Recent molecules with unknown mode of action; P = host plant
defense inducers. Source: http://www.frac.info/ (FRAC = Fungicide Resistance Action Committee). Be sure to read a current product label before applying any
chemicals.




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