• TABLE OF CONTENTS
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 Copyright
 The causal fungi
 Symptoms
 Significance of fusarium wilt
 Control
 Chemotherapy-high lime all nitrate...
 Fusarium stem rot, a disease that...
 Reference
 Tables






Group Title: Research report - Bradenton Agricultural Research & Education Center - GC1976-16
Title: Fusarium wilt of chyrsanthemum, caused by Fusarium Oxysporum
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00067706/00001
 Material Information
Title: Fusarium wilt of chyrsanthemum, caused by Fusarium Oxysporum
Series Title: Bradenton AREC research report
Physical Description: 5 leaves : ; 28 cm.
Language: English
Creator: Engelhard, Arthur W
Woltz, S. S
Agricultural Research & Education Center (Bradenton, Fla.)
Publisher: Agricultural Research & Education Center, IFAS, University of Florida
Place of Publication: Bradenton Fla
Publication Date: 1976
 Subjects
Subject: Chrysanthemums -- Diseases and pests -- Florida   ( lcsh )
Fusarium oxysporum -- Control -- Florida   ( lcsh )
Fusarium diseases of plants -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (leaf 4).
Statement of Responsibility: Arthur W. Engelhard and S.S. Woltz.
General Note: Caption title.
General Note: "November 1976."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067706
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, Board of Trustees of the University of Florida
Resource Identifier: oclc - 72468488

Table of Contents
    Copyright
        Copyright
    The causal fungi
        Page 1
    Symptoms
        Page 1
    Significance of fusarium wilt
        Page 2
    Control
        Page 2
    Chemotherapy-high lime all nitrate nitrogen cultural control
        Page 3
    Fusarium stem rot, a disease that resembles fusarium wilt
        Page 3
    Reference
        Page 4
    Tables
        Page 5
Full Text





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used only to trace the historic work of
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Copyright 2005, Board of Trustees, University
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AGRICULTURAL RESEARCH & EDUCATION CENTER
SIFAS, University of Florida
SBradenton

Bradenton AREC Research Report GC1976-16 THovember 1976

FUSARIUL WILT OF CHRYSANTHEMIUI, CAUSED BY FUSARIUM OXYSPOPUM

Arthur I. Engelhard and S. S. Woltz

Fusarium wilt of chrysanthemum apparently has been present in Florida for over
25 years. Pathologists over the years have observed wilting plants with symptoms
similar to what is now known as Fusarium wilt. They isolated Fusarium sp. from wilt-
ing plants but, until more recent years, were not successful in artificially inocu-
lating plants.

Only a few chrysanthemum growers in Florida have been troubled with Fusarium
wilt. Due to the nature of the disease, it is expected that the disease will spread
to other locations and more growers will experience troubles with Fusarium wilt in
the future. .'

THE CAUSAL FUNGI '
___ ___ i'rt
There are two fungi known to cause Fusarium wilt in chrysanthemum OTri ne, called
Fusarium oxysporum f. sp. chrysanthemi, is common in Florida and is known to qccur
only on chrysanthemums. The other, Fusarium oxysporum f. sp. tracheiphilum ,ra2e 1, /
is known to occur on certain cultivars of southern peas cowpeaa) and/certain culti-
vars of chrysanthemum. The two fungi do not attack equally all cultivars,of chrysan-
themum. For example, Encore is very susceptible to both of the wilt fungli"r;Southern
Comfort is susceptible to the chrysanthemi wilt fungus and apparently resistant -to
the tracheiphilum race 1 wilt fungus. Escapade had more disease with the tracheiphi-
lum race 1 fungus than with the chrysanthemi fungus. Stingray appears to be resis-
tant to both wilt fungi. The reaction of chrysanthemum cultivars to the two wilt
fungi is given in Tables 1 and 2.

SYMPTOMS

When conditions for disease development are optimum the initial symptoms of
Fusarium wilt include unilateral (one side of a leaf) chlorosis or yellowing of one
or more leaves at or near the stem tip and slight to pronounced curvature of the
chlorotic leaves and the stem toward the affected side of the plant. As disease
progresses, chlorosis of the affected leaves becomes more general and severely affec-
ted leaves wilt. Wilting leaves occur initially on the most severely affected side
of the plant, but as disease progresses the entire plant wilts and dies. Symptoms
on the more resistant cultivars include leaf chlorosis, stunting of the leaves and
reduced rate of plant growth. These symptoms may be so mild that they resemble a
nutritional disorder or so severe that after extended periods of leaf chlorosis, stem
necrosis and death of the plant follows. Black necrosis of the stem sometimes occurs.
It may extend from the roots into the upper parts of the stem. In some instances the
black necrosis occurs only in the upper parts of the stem and has no externally visi-
ble connection with the base or tip of the plant.

Vascular discoloration occurs in the stems and sometimes in the leaves. In the
stem, various intensities of brown to reddish-brown discoloration are associated with
foliar symptoms. Vascular discoloration may be externally visible in leaf veins on
some cultivars, but is uncommon. On Yellow Delaware and Delaware, vascular discolo-
ration of leaf veins is one of the earliest symptoms. In greenhouse experiments,
leaf symptoms showed 7 days after inoculation on a very susceptible cultivar like
Yellow Delaware but not until 35 days on a more resistant one like Bluechip.





AGRICULTURAL RESEARCH & EDUCATION CENTER
SIFAS, University of Florida
SBradenton

Bradenton AREC Research Report GC1976-16 THovember 1976

FUSARIUL WILT OF CHRYSANTHEMIUI, CAUSED BY FUSARIUM OXYSPOPUM

Arthur I. Engelhard and S. S. Woltz

Fusarium wilt of chrysanthemum apparently has been present in Florida for over
25 years. Pathologists over the years have observed wilting plants with symptoms
similar to what is now known as Fusarium wilt. They isolated Fusarium sp. from wilt-
ing plants but, until more recent years, were not successful in artificially inocu-
lating plants.

Only a few chrysanthemum growers in Florida have been troubled with Fusarium
wilt. Due to the nature of the disease, it is expected that the disease will spread
to other locations and more growers will experience troubles with Fusarium wilt in
the future. .'

THE CAUSAL FUNGI '
___ ___ i'rt
There are two fungi known to cause Fusarium wilt in chrysanthemum OTri ne, called
Fusarium oxysporum f. sp. chrysanthemi, is common in Florida and is known to qccur
only on chrysanthemums. The other, Fusarium oxysporum f. sp. tracheiphilum ,ra2e 1, /
is known to occur on certain cultivars of southern peas cowpeaa) and/certain culti-
vars of chrysanthemum. The two fungi do not attack equally all cultivars,of chrysan-
themum. For example, Encore is very susceptible to both of the wilt fungli"r;Southern
Comfort is susceptible to the chrysanthemi wilt fungus and apparently resistant -to
the tracheiphilum race 1 wilt fungus. Escapade had more disease with the tracheiphi-
lum race 1 fungus than with the chrysanthemi fungus. Stingray appears to be resis-
tant to both wilt fungi. The reaction of chrysanthemum cultivars to the two wilt
fungi is given in Tables 1 and 2.

SYMPTOMS

When conditions for disease development are optimum the initial symptoms of
Fusarium wilt include unilateral (one side of a leaf) chlorosis or yellowing of one
or more leaves at or near the stem tip and slight to pronounced curvature of the
chlorotic leaves and the stem toward the affected side of the plant. As disease
progresses, chlorosis of the affected leaves becomes more general and severely affec-
ted leaves wilt. Wilting leaves occur initially on the most severely affected side
of the plant, but as disease progresses the entire plant wilts and dies. Symptoms
on the more resistant cultivars include leaf chlorosis, stunting of the leaves and
reduced rate of plant growth. These symptoms may be so mild that they resemble a
nutritional disorder or so severe that after extended periods of leaf chlorosis, stem
necrosis and death of the plant follows. Black necrosis of the stem sometimes occurs.
It may extend from the roots into the upper parts of the stem. In some instances the
black necrosis occurs only in the upper parts of the stem and has no externally visi-
ble connection with the base or tip of the plant.

Vascular discoloration occurs in the stems and sometimes in the leaves. In the
stem, various intensities of brown to reddish-brown discoloration are associated with
foliar symptoms. Vascular discoloration may be externally visible in leaf veins on
some cultivars, but is uncommon. On Yellow Delaware and Delaware, vascular discolo-
ration of leaf veins is one of the earliest symptoms. In greenhouse experiments,
leaf symptoms showed 7 days after inoculation on a very susceptible cultivar like
Yellow Delaware but not until 35 days on a more resistant one like Bluechip.







Foliage symptom development is very dependent on temperature. Severe symptoms
develop at 800 and 90 F, very mild at 700 and none at 600 and 50.

SIGNIFICANCE OF FUSARIUI WILT

The great danger with Fusarium wilt lies in the difficulty in controlling the
disease once it becomes established on a farm. The fungus can live in the soil for
an indefinite number of years. It can potentially survive under greenhouse benches,
in field soils, in saran house post rows, around buildings and even in wood (bench
supports). It was demonstrated by Drs. Jones and Woltz at the University of Flor-
ida Agricultural Research and Education Center, Bradenton, that the tomato Fusariun
wilt fungus can live in tomato stakes and can be spread to non-infested fields on
the stakes. The wilt fungi can grow in nutrient solutions, in hoses and in water-
ing systems (Chapin lines). It can be spread by wind.and running water, with soil
on equipment, on shoes and under fingernails. It can be spread on tools used in
taking cuttings and on cuttings themselves. The use of "home-grown" or non-indexed
cuttings may provide a source of the fungus. Experience has indicated that Fusarium
wilt increases slowly on a chrysanthemum farm when it is not controlled. It causes
very little loss and concern the first year it is observed. Losses increase the
second year but are not large enough to divert the growers attention from other
problems. The third year, significant losses occur, and the disease is well estab-
lished and difficult to control.

CONTROL

Fusarium wilt should be prevented from occurring rather than treating the prob-
lem after it exists. Methods of preventing or controlling Fusarium wilt are:

1. Use as tolerant a cultivar for specific needs as possible. Remember,
however, that the fungus can live in cultivars showing few or no out-
ward symptoms.

2. Obtain cuttings from a source that uses culture-indexed stock. Fusarium
wilt can be carried in cuttings.

3. Plant only in sterilized soil.

4. If Fusarium wilt is present,
a. Sterilize hands, hoses, "spaghetti" watering systems, benches
and all other equipment that comes in contact with the plants
or pots. Flush out hoses and watering systems with clorox,
LF-10, or other suitable disinfectant.

b. Keep feet off benches, keep fingers and tools out of pots unless
first dipped in alcohol or other suitable disinfectant.

c. Carefully remove infected plants and any containers used by placing
in a plastic bag where they are growing and remove from the growing
site. Bury or haul to dump at least one mile away. Do not spread
soil from the infested location clear to the exit.

d. Spot fumigate the infested site immediately.

e. Try an experiment with a benomyl-high lime (high pH)-all nitrate
nitrogen growth regime to control Fusarium wilt on potted plants.
The method is described below.







Foliage symptom development is very dependent on temperature. Severe symptoms
develop at 800 and 90 F, very mild at 700 and none at 600 and 50.

SIGNIFICANCE OF FUSARIUI WILT

The great danger with Fusarium wilt lies in the difficulty in controlling the
disease once it becomes established on a farm. The fungus can live in the soil for
an indefinite number of years. It can potentially survive under greenhouse benches,
in field soils, in saran house post rows, around buildings and even in wood (bench
supports). It was demonstrated by Drs. Jones and Woltz at the University of Flor-
ida Agricultural Research and Education Center, Bradenton, that the tomato Fusariun
wilt fungus can live in tomato stakes and can be spread to non-infested fields on
the stakes. The wilt fungi can grow in nutrient solutions, in hoses and in water-
ing systems (Chapin lines). It can be spread by wind.and running water, with soil
on equipment, on shoes and under fingernails. It can be spread on tools used in
taking cuttings and on cuttings themselves. The use of "home-grown" or non-indexed
cuttings may provide a source of the fungus. Experience has indicated that Fusarium
wilt increases slowly on a chrysanthemum farm when it is not controlled. It causes
very little loss and concern the first year it is observed. Losses increase the
second year but are not large enough to divert the growers attention from other
problems. The third year, significant losses occur, and the disease is well estab-
lished and difficult to control.

CONTROL

Fusarium wilt should be prevented from occurring rather than treating the prob-
lem after it exists. Methods of preventing or controlling Fusarium wilt are:

1. Use as tolerant a cultivar for specific needs as possible. Remember,
however, that the fungus can live in cultivars showing few or no out-
ward symptoms.

2. Obtain cuttings from a source that uses culture-indexed stock. Fusarium
wilt can be carried in cuttings.

3. Plant only in sterilized soil.

4. If Fusarium wilt is present,
a. Sterilize hands, hoses, "spaghetti" watering systems, benches
and all other equipment that comes in contact with the plants
or pots. Flush out hoses and watering systems with clorox,
LF-10, or other suitable disinfectant.

b. Keep feet off benches, keep fingers and tools out of pots unless
first dipped in alcohol or other suitable disinfectant.

c. Carefully remove infected plants and any containers used by placing
in a plastic bag where they are growing and remove from the growing
site. Bury or haul to dump at least one mile away. Do not spread
soil from the infested location clear to the exit.

d. Spot fumigate the infested site immediately.

e. Try an experiment with a benomyl-high lime (high pH)-all nitrate
nitrogen growth regime to control Fusarium wilt on potted plants.
The method is described below.







CHE:IOTHERAPY-HIGH LIME-ALL NITRATE NITROGEN CULTURAL CONTROL

Research at the University of Florida Agricultural Research and Education
Center, Bradenton, has demonstrated for the first time a method of controlling
Fusarium wilt. It is possible to control Fusarium wilt on potted chrysanthemums by
using a relatively high amount of lime in the potting mix, a specific type of nitro-
gen fertilizer and a drench with one of the newer systemic fungicides. It is impor-
tant to recognize that chemical alone, or lime alone, or proper nitrogen source
alone would not be expected to control Fusarium wilt, but an integrated programmed
approach using all three methods does provide control.

Where there is a history of Fusarium wilt on potted chrysanthemums, the follow-
ing measures should be tried on an experimental basis:

Prior to planting, add hydrated lime and ground limestone in a 2 to 1 ratio to
raise the soil pHl to 7.0. In the complete fertilizer, use an all-nitrate form of
nitrogen (potassium, calcium or sodium nitrate) as this reduces Fusarium wilt
development. An ammonium source of nitrogen (ammonium nitrate, ammonium sulfate)
increases the development of Fusarium wilt and also causes the pH of the soil to go
down. Drench the pots with benomyl 50!1 fungicide. For 6" pots, use 8 ounces of a
suspension containing benomyl 501 at 1/4 lb/100 gals. Apply at planting and 2 weeks
later. Plants would not be expected to recover if treated after infection occurs.
In the field use 20 pounds per acre. The trial of the benomyl-lime-nitrate control
procedure should be made on a limited basis to learn whether the individual grower
practices permit good production of quality chrysanthemums under specific growing
conditions. Lime plus nitrogen derived mainly or solely from nitrate sources will
cause high soil pH values that may cause problems so proceed on a limited scale.
Remember that benomyl 50W, lime and nitrate fertilizer each contributes to disease
control but only by using an integrated, programmed approach using all three factors
can complete disease control be expected.

Problems with micronutrient deficiencies may develop when chrysanthemums are
grown at this pll. However, deficiencies usually can be prevented by spraying the
foliage with iron, manganese, zinc and also magnesium as needed possibly as often
as once per week. The micronutrients can be added to regular pesticide sprays if
there are no compatibility and phytotoxicity problems and they also may be added
to the regular fertilizer. Iron deficiency has been the most frequently encountered
complication but much would depend on the growing medium and fertilizer program
being used.

FUSARIUM STEM ROT, A DISEASE THAT RESEMBLES FUSARIIPI WILT

A recently discovered disease in Florida, called Fusarium stem rot, is diffi-
cult to distinguish from Fusarium wilt in chrysanthemum plantings. Fusarium stem
rot, caused by the fungus Fusarium solani, affects flowering plants, stock plants,
and cuttings in propagation. Wilting may occur with either disease. Early symptoms
may aid in identification. F. solani causes a red to brown pith discoloration at
some location in the stem, whereas the dark discoloration caused by the Fusarium
wilt fungus is limited to the vascular strands. Also the stem and leaf curvature
typical of Fusarium wilt is not present with stem rot. Development of adventitious
shoots from the crown or basal stem area after the stem dies occurs frequently with
stem rot, but not with Fusarium wilt. Dark streaks on the stem extending upward
from the base of a plant or developing in the upper parts of a plant are common to
both diseases. The dark streaks extend to the vascular tissues in Fusarium wilt,







CHE:IOTHERAPY-HIGH LIME-ALL NITRATE NITROGEN CULTURAL CONTROL

Research at the University of Florida Agricultural Research and Education
Center, Bradenton, has demonstrated for the first time a method of controlling
Fusarium wilt. It is possible to control Fusarium wilt on potted chrysanthemums by
using a relatively high amount of lime in the potting mix, a specific type of nitro-
gen fertilizer and a drench with one of the newer systemic fungicides. It is impor-
tant to recognize that chemical alone, or lime alone, or proper nitrogen source
alone would not be expected to control Fusarium wilt, but an integrated programmed
approach using all three methods does provide control.

Where there is a history of Fusarium wilt on potted chrysanthemums, the follow-
ing measures should be tried on an experimental basis:

Prior to planting, add hydrated lime and ground limestone in a 2 to 1 ratio to
raise the soil pHl to 7.0. In the complete fertilizer, use an all-nitrate form of
nitrogen (potassium, calcium or sodium nitrate) as this reduces Fusarium wilt
development. An ammonium source of nitrogen (ammonium nitrate, ammonium sulfate)
increases the development of Fusarium wilt and also causes the pH of the soil to go
down. Drench the pots with benomyl 50!1 fungicide. For 6" pots, use 8 ounces of a
suspension containing benomyl 501 at 1/4 lb/100 gals. Apply at planting and 2 weeks
later. Plants would not be expected to recover if treated after infection occurs.
In the field use 20 pounds per acre. The trial of the benomyl-lime-nitrate control
procedure should be made on a limited basis to learn whether the individual grower
practices permit good production of quality chrysanthemums under specific growing
conditions. Lime plus nitrogen derived mainly or solely from nitrate sources will
cause high soil pH values that may cause problems so proceed on a limited scale.
Remember that benomyl 50W, lime and nitrate fertilizer each contributes to disease
control but only by using an integrated, programmed approach using all three factors
can complete disease control be expected.

Problems with micronutrient deficiencies may develop when chrysanthemums are
grown at this pll. However, deficiencies usually can be prevented by spraying the
foliage with iron, manganese, zinc and also magnesium as needed possibly as often
as once per week. The micronutrients can be added to regular pesticide sprays if
there are no compatibility and phytotoxicity problems and they also may be added
to the regular fertilizer. Iron deficiency has been the most frequently encountered
complication but much would depend on the growing medium and fertilizer program
being used.

FUSARIUM STEM ROT, A DISEASE THAT RESEMBLES FUSARIIPI WILT

A recently discovered disease in Florida, called Fusarium stem rot, is diffi-
cult to distinguish from Fusarium wilt in chrysanthemum plantings. Fusarium stem
rot, caused by the fungus Fusarium solani, affects flowering plants, stock plants,
and cuttings in propagation. Wilting may occur with either disease. Early symptoms
may aid in identification. F. solani causes a red to brown pith discoloration at
some location in the stem, whereas the dark discoloration caused by the Fusarium
wilt fungus is limited to the vascular strands. Also the stem and leaf curvature
typical of Fusarium wilt is not present with stem rot. Development of adventitious
shoots from the crown or basal stem area after the stem dies occurs frequently with
stem rot, but not with Fusarium wilt. Dark streaks on the stem extending upward
from the base of a plant or developing in the upper parts of a plant are common to
both diseases. The dark streaks extend to the vascular tissues in Fusarium wilt,




-4-


but with stem rot they may be present, but not always, only in the epidermal
and/or outer cortical tissues. The cultivars affected by these two organisms
are distinctive. The Iceberg family is susceptible to stem rot but tolerant
to Fusarium wilt. The Torches are susceptible to both diseases. Knowing the
reactions of the cultivars also provides a clue to the organism involved. Field
diagnosis is difficult and for accurate diagnosis, tissue isolations must be
made from diseased plant parts for both Fusarium diseases.



REFERENCES


Engelhard, Arthur W. 1971. Fusarium wilt of chrysanthemum: Symptomatology
and cultivar reactions. Proc. Fla. State Hort. Soc. 84:351-354.

Engelhard, Arthur H., G. L. Crane and Ii. C. Mellinger. 1976. Stem rot, a new
disease on chrysanthemum incited by Fusarium solani. Plant Disease Repor-
ter 60:437-441.

Engelhard, Arthur W., and S. S. Woltz. 1973. Fusarium wilt of chrysanthemum:
Complete control of symptoms with an integrated fungicide-lime-nitrate
regime. Phytopathology 63:1256-1259.










Table 1. Reactions of chrysanthemum cultivars to Fusarium wilt fungi.

The following cultivars were grown in replicated tests in 6" pots in the green-
house. They were inoculated by cutting slits in the soil to injure the roots.
A Fusarium spore suspension was poured into the cuts in the soil.

.. Foliage symptoms of F. oxysporum
Cultivar f. sp. chrysanthemi f. sp. tracheiphilum race 1

Bluechip mild none
Delaware severe none
Encore severe severe
Escapade mild severe
Giant #4 Indianapolis Yellow mild none
Hostess severe severe
Iceberg mild none
CF 773 Marguerite R mild none
Maytime severe severe
Nob Hill severe none
Southern Comfort severe none
Tinsel none
Torch mild none
White Marble mild none
White Sands severe none
'inter Carnival severe mild
Yellow Bonnie Jean severe none
Yellow Delaware severe none


Commercially produced plants observed with Fusarium wilt
Bonnie Jean, Deep Ridge, Delaware, Harguerite, Nob Hill,
Ann, Torch, Yellow Delaware.


include Always Pink,
Orange Bowl, Princess


Table 2. Chrysanthemum cultivars showing no foliage symptoms after inoculation
with each of the two Fusarium wilt fungi.

The following cultivars were grown in replicated tests in 6" pots in the green-
house. They were inoculated by cutting slits in the soil to injure the roots.
A Fusarium spore suspension was poured into the cuts in the soil. No foliage
symptoms were present when the plants were mature and flowering. Further tests
are needed to determine if they are resistant to the Fusarium wilt fungi.


Albatross
Bright Golden Ann
Cavalier
Darkchip
Dillon Beauregard
Dolly
Donlopes White Spider
Donlopes Yellow Spider
Explorer
Improved Indianapolis Yellow
CF #2 Indianapolis Bronze
Luyona
Mandalay


Maple Leaves
Hay Shoesmith
'lrs. Roy
Nimrod
Pinocchio
Polaris
Puritan
Showoff
Southern Sun
Statesman
Stingray
Treasure Chest
Tuneful
Yellow Knight


t




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