• TABLE OF CONTENTS
HIDE
 Alternaria rot
 Anthracnose fruit rot
 Botrytis fruit rot or gray...
 Colletotrichum crown rot
 Leaf scorch
 Charcoal rot
 Phytophthora crown rot
 Phytoplasma diseases
 Powdery mildew
 Rhizopus rot or leak
 Stem-end rot and leaf blotch
 Verticillium wilt
 Tables
 Footnotes






Group Title: 2006 Florida plant disease management guide: strawberry
Title: Florida plant disease management guide, 2006: strawberry
CITATION PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00066847/00001
 Material Information
Title: Florida plant disease management guide, 2006: strawberry
Physical Description: Book
Language: English
Creator: Peres, Natalia A.
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2006
 Notes
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00066847
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
    Alternaria rot
        Page 1
    Anthracnose fruit rot
        Page 2
    Botrytis fruit rot or gray mold
        Page 3
        Page 4
    Colletotrichum crown rot
        Page 5
    Leaf scorch
        Page 6
    Charcoal rot
        Page 7
    Phytophthora crown rot
        Page 8
    Phytoplasma diseases
        Page 9
    Powdery mildew
        Page 10
    Rhizopus rot or leak
        Page 11
    Stem-end rot and leaf blotch
        Page 12
    Verticillium wilt
        Page 13
    Tables
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
    Footnotes
        Page 20
Full Text
2006 Florida Plant Disease Management Guide: Strawberry


Whole Document Navigator (Click Here)


Printer r
Friendly
,.. 11,=. 0r111r Version


:..,...,,.... ........ ..... I %H E ,3


UF^ UNIVERSITY of
UF FLORIDA
IFAS Extension


2006 Florida Plant Disease Management Guide:

Strawberry

Natalia A. Peres-

Alternaria Rot

Altemaria 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.


Figure 1. Altemaria Rot.

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.


U


i


W rN.'",


iIn,




2006 Florida Plant Disease Management Guide: Strawberry


Symptoms

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




2006 Florida Plant Disease Management Guide: Strawberry


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 B. ,I, y1I cinerea.













Figure 3. Anthracnose Fruit Rot.

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.

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




2006 Florida Plant Disease Management Guide: Strawberry


Botrytis fruit rot, also known as gray mold, caused by B. ',yi,, 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.

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 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.




2006 Florida Plant Disease Management Guide: Strawberry


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.













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


Management

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 ofFragaria 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.

Chemical: See Table 1 .


Leaf Spot

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




2006 Florida Plant Disease Management Guide: Strawberry


plants.

Causal organism

The fungus is considered to be pathogenic only to species and cultivars ofFragariae 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 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




2006 Florida Plant Disease Management Guide: Strawberry


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.


Figure 6. Phomopsis Leaf Blight.


Figure 7. Phomopsis Soft Rot.

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
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.

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 andP. citricola, can be a serious disease
of annual production strawberry in central Florida.




2006 Florida Plant Disease Management Guide: Strawberry


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.




2006 Florida Plant Disease Management Guide: Strawberry


Management

Cultural: Use of disease-free transplants.


Powdery Mildew

Powdery mildew, caused by Sl/lVhI. I//. i 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.

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




2006 Florida Plant Disease Management Guide: Strawberry


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.


Figure 10. Rhizopus rot or leak.

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

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




2006 Florida Plant Disease Management Guide: Strawberry


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.

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.




2006 Florida Plant Disease Management Guide: Strawberry


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.


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.

Disease cycle and epidemiology

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.




2006 Florida Plant Disease Management Guide: Strawberry


Figure 13. Verticillium Wilt.


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.


Tables

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


* Chemical


Abound

(azoxystrobin)


Fungicide
Group a


11


Maximum
Rate/ Acre/

Applic. Season


15.4
fl. oz.


1.92
qt.


Min.
Days to
Harvest


0


Pertinent
Diseases or
Pathogents


Anthracnose

Powdery mildew

Botrytis
(suppression
only)


Remarks


Do not make
more than 2
sequential
applications
and no more
than 4
applications
per crop year.
See label for
instructions
on dipping
transplants




2006 Florida Plant Disease Management Guide: Strawberry


Aliette WDG

(fosetyl-Al)


Cabrio EG

(pyraclostrobin)


Captan 50 WP

captain )


Captan 80 WDG

captain )


Captec 4L

captain )






Captevate 68 WDG

captainn + fenhexamid)


33


11


M3


M3


M3


M3 + 17


5 lb.


14 fl.
oz.


30 lb.


70 fl.
oz.


6 lb. 48 lb.


3.75
lb.


30 lb.


3 qt. 24 qt.


5.25
lb.


21 lb.


12 hr


0


1


1


0


Phytophthora
diseases




Anthracnose

Leaf spot

Powdery mildew

Botrytis
(suppression
only)


Anthracnose

Botrytis fruit rot

Leaf spot


Anthracnose

Botrytis fruit rot

Leaf spot


Anthracnose

Botrytis fruit rot

Leaf spot





Botrytis fruit rot


Anthracnose


Do not tank
mix with
copper
fungicides


Do not make
more than 2
sequential
applications
and no more
than 5
applications
per crop year




Rate per
treated acre.
Special label
for FL allows
up to 24
applications
per season



Rate per
treated acre.
Special label
for FL allows
up to 24
applications
per season



Rate per
treated acre.
Special label
for FL allows
up to 24
applications
per season



Do not make
more than 2
consecutive
applications




2006 Florida Plant Disease Management Guide: Strawberry


Copper


(many brands)1





Elevate 50 WDG

(fenhexamid)


Nova 40W

(myclobutanil)




Potassium
bicarbonate (many
brands)2


Potassium phosphite
(many brands)3


Pristine

(pyraclostrobin +
boscalid)


Ml or M9


17


3


11+7


varies


1.5 lb.


5 oz.


varies


varies


23 oz.


varies


6 lb.


30 oz.


varies


varies


115
oz.


1-2


0


0


1


0


0


Angular leaf spot


Botrytis fruit rot





Powdery mildew

Leaf spot

Leaf blight


Powdery mildew


Phytophthora
diseases





Botrytis fruit rot

Anthracnose

Powdery mildew


Leaf spot


Frequent use
of copper
fungicides
may cause
foliar bum



Do not make
more than 2
consecutive
applications



Do not plant
rotational
crops until 30
days after last
application



Do not mix
with highly
acid products



May cause
foliar bum if
applied with
copper based
products



Do not make
more than 2
consecutive
applications
and no more
than 5
applications
per crop




2006 Florida Plant Disease Management Guide: Strawberry


Procure 50WS

(triflumizole)









Ridomil Gold EC

(metalaxyl-M)


Rovral 4

(iprodione)


Rovral 75 WG

(iprodione)


3


4


2


2


8 oz. 32 oz.


1 pt/
trtd.
acre


2 pt.


1.33


1 V2
qts/
trtd
acre


2 pt.


1.33


1


N/A


N/A


Powdery mildew


Phytophthora
diseases




Botrytis fruit rot

Stem end rot

Phomopsis soft
rot

Leaf spot



Botrytis fruit rot

Stem end rot

Phomopsis soft
rot


Leaf spot


Do not plant
leafy
vegetables
within 30
days or root
vegetables
within 60
days or
rotational
crops not on
label for one
year after
application



See label for
use in drip
irrigation


Do not make
more than 1
application
per season.
Do not apply
after bloom
initiation


Do not make
more than 1
application
per season.
Do not apply
after bloom
initiation




2006 Florida Plant Disease Management Guide: Strawberry


Scala SC

(pyrimethanil)


Serenade Max

(Bacillus subtilis)




Sulfur


(many brands)4


Switch 62.5 WG

(cyprodinil +
fludioxonil)


Thiram 65 WSB

(thiram)


9


Ml or M9


9+12


M2


18 fl.
oz.


3 lb.


varies


54 fl.
oz.


varies


14 oz. 56 oz.


5 lb. 25 lb.


1


0


1


0


3


Botrytis fruit rot









Powdery mildew

Botrytis fruit rot

Anthracnose


Powdery mildew


Botrytis fruit rot

Anthracnose


Botrytis fruit rot


Do not make
more than 2
consecutive
applications.
Do not use
more than 2
of 6
applications
in any one
season.



Should be
used in
combination
with other
fungicides



Do not use
during hot
weather



Do not make
more than 2
consecutive
applications.
Do not plant
crops not on
the label for
30 days after
last
application



Do not rotate
treated crops
with other
crops for
which Thiram
is not
registered




2006 Florida Plant Disease Management Guide: Strawberry


Topsin 4.5 L

(thiophanate-methyl)


Topsin M 70 W,

Topsin M WSB

(thiophanate-methyl)


1


1


20 fl.
oz.


80 fl.
oz


1 lb. I4 lb.


1


1


Botrytis fruit rot

Colletotrichum
crown rot

Leaf scorch

Leaf blight

Powdery mildew


Botrytis fruit rot

Colletotrichum
crown rot

Leaf scorch

Leaf blight

Powdery mildew


Do not use
Topsin alone.
Fungicides
from different
chemical
groups should
be used in
spray
program for
disease
resistance
management



Do not use
Topsin alone.
Fungicides
from different
chemical
groups should
be used in
spray
program for
disease
resistance
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

4 e.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.




2006 Florida Plant Disease Management Guide: Strawberry


Footnotes

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. For
more information on obtaining other extension publications, contact your county Cooperative
Extension service.

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.




Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural
Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all
conventions, but permits free reproduction by all agents and offices of the Cooperative Extension
Service and the people of the State of Florida. Permission is granted to others to use these materials
in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the
publication, its source, and date of publication.




University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs