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 Copyright
 The causal fungi
 Symptoms
 Significance of Fusarium wilt
 Control
 Chemotherapy - high lime-all nitrate...






Group Title: Mimeo report - Bradenton Agricultural Research & Education Center - GC-1972-1
Title: Fusarium wilt of chrysanthemum
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00067672/00001
 Material Information
Title: Fusarium wilt of chrysanthemum
Series Title: Bradenton AREC mimeo report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Engelhard, Arthur W
Woltz, S. S
Agricultural Research & Education Center (Bradenton, Fla.)
Publisher: Agricultural Research & Education Center
Place of Publication: Bradenton Fla.
Publication Date: 1972
 Subjects
Subject: Chrysanthemums -- Diseases and pests -- Florida   ( lcsh )
Fusarium diseases of plants -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Arthur W. Engelhard and S.S. Woltz.
General Note: Caption title.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067672
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 - 71837275

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
        Page 4
Full Text





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Agricultural Sciences and should be
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site maintained by the Florida
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Copyright 2005, Board of Trustees, University
of Florida




100


AGRICULTURAL RESEARCH & EDUCATION CENTER
/I Bradenton, Florida

t-.jBradenton AREC Mimeo Report GC-1972-1 HUME L.IRARRY7

FUSARIUM WILT OF CHRYSANTHEMUM MAY 1 1972

Arthur W. Engelhard and S. S. Wo tz

Fusarium wilt of chrysanthemum apparently has been lFeAgSt nfVPof cF'ia
over 25 years. Pathologists over the years have observedtw 1 --TWi" ?ns th-I
symptoms similar to what is now known as Fusarium wilt. They isolated Fusarium
sp. from wilting plants but, until more recent years, were not successful in
artificially inoculating 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

There are two fungi known to cause Fusarium wilt in chrysanthemum. One,
called Fusarium oxysporum f. sp. chrysanthemi, is common in Florida and is known
to occur only on chrysanthemums. The other, Fusarium oxysporum f. sp. tracheiphilum
race 1, is known to occur on certain cultivars of southern peas cowpeaa) and certain
cultivars of chrysanthemums. The two fungi do not attack equally all cultivars of
chrysanthemum. For example, Encore is very susceptible to both of the wilt fungi.
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 tracheiphilum race 1 fungus than with the chrysanthemi fungus. Stingray
appears to be resistant to both wilt fungi. The reaction of chrysanthemum culti-
vars 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 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, chlor-
osis of the affected leaves becomes more general and severely affected 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 nutri-
tional 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 visible connection with the base or tip of the plant.

Vascular discoloration occurs in the stems and in the leaves. In the stem
various intensities of brown to reddish brown discoloration are associated with
foliar symptoms. Vascular discoloration externally visible in leaf veins occurs
on some cultivars but is uncommon. On Yellow Delaware and Delaware, vascular
discoloration 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.




100


AGRICULTURAL RESEARCH & EDUCATION CENTER
/I Bradenton, Florida

t-.jBradenton AREC Mimeo Report GC-1972-1 HUME L.IRARRY7

FUSARIUM WILT OF CHRYSANTHEMUM MAY 1 1972

Arthur W. Engelhard and S. S. Wo tz

Fusarium wilt of chrysanthemum apparently has been lFeAgSt nfVPof cF'ia
over 25 years. Pathologists over the years have observedtw 1 --TWi" ?ns th-I
symptoms similar to what is now known as Fusarium wilt. They isolated Fusarium
sp. from wilting plants but, until more recent years, were not successful in
artificially inoculating 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

There are two fungi known to cause Fusarium wilt in chrysanthemum. One,
called Fusarium oxysporum f. sp. chrysanthemi, is common in Florida and is known
to occur only on chrysanthemums. The other, Fusarium oxysporum f. sp. tracheiphilum
race 1, is known to occur on certain cultivars of southern peas cowpeaa) and certain
cultivars of chrysanthemums. The two fungi do not attack equally all cultivars of
chrysanthemum. For example, Encore is very susceptible to both of the wilt fungi.
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 tracheiphilum race 1 fungus than with the chrysanthemi fungus. Stingray
appears to be resistant to both wilt fungi. The reaction of chrysanthemum culti-
vars 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 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, chlor-
osis of the affected leaves becomes more general and severely affected 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 nutri-
tional 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 visible connection with the base or tip of the plant.

Vascular discoloration occurs in the stems and in the leaves. In the stem
various intensities of brown to reddish brown discoloration are associated with
foliar symptoms. Vascular discoloration externally visible in leaf veins occurs
on some cultivars but is uncommon. On Yellow Delaware and Delaware, vascular
discoloration 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 symp-
toms develop at 800 and 900 F, very mild at 700 and none at 600 and 500.

SIGNIFICANCE OF FUSARIUM WILT

The great danger with Pusarium wilt lies in the difficulty in controlling the
disease once it becomes established on a farm. Generally, only limited information
is available for the chrysanthemum wilt disease because of its "newness". (Although
wilting -chrysanth=rum plants have been seen-for-many years, the disease was proven
to be.caused by the two specific wilt fungi in 19.65 and 1970 for'the tracheiphilum
race 1 and the chrysanthemi fungi., respectively). However, ore can draw on infor-
mation available about Fu.ariuil wilt-diseases of other crops for the Fusarium
wilt diseases of chrysanthcmums.are not thought to be significantly different.

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 Florida Research and Education Center,
Bradenton, that the tomato Fusarium wilt fungus can live in tomato stakes and can
be spre-ad to non-infes-ted fields on the stakes. The wilt fungi can grow in nutri-
ent solutions, in hoses and in watering 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 ndidcated 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. Loses 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 established and.difficult to-control.

CONTROL

Fusarium wilt should be prevented from occurring rather than treating the
problem after it exists. Hlethods of preventing or controlling Fusarium wilt are -

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

2. Obtain cutting- ,from a source that uses culture-indexed stock. Stock
is indexed (labo:_.tcry type culture) for several diseases and watched
for Fusarium w:ilt if not already included in the indexing program.
Fusarium wilt can be carried in cuttings.

3. Plant only in steLilised soil.

4. If Fusarium wilt is present,
a. Sto~iLi.?. b:I., hoses, "spaghetti" watering systems, benches
and all other equipment that comes in contact with the plants
c: pets. Flu';h out hoses am.d Twtering systems with chlorox,
LF 1C, or ot:er suitable disinfectant.

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










Foliage symptom development is very dependent on temperature. Severe symp-
toms develop at 800 and 900 F, very mild at 700 and none at 600 and 500.

SIGNIFICANCE OF FUSARIUM WILT

The great danger with Pusarium wilt lies in the difficulty in controlling the
disease once it becomes established on a farm. Generally, only limited information
is available for the chrysanthemum wilt disease because of its "newness". (Although
wilting -chrysanth=rum plants have been seen-for-many years, the disease was proven
to be.caused by the two specific wilt fungi in 19.65 and 1970 for'the tracheiphilum
race 1 and the chrysanthemi fungi., respectively). However, ore can draw on infor-
mation available about Fu.ariuil wilt-diseases of other crops for the Fusarium
wilt diseases of chrysanthcmums.are not thought to be significantly different.

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 Florida Research and Education Center,
Bradenton, that the tomato Fusarium wilt fungus can live in tomato stakes and can
be spre-ad to non-infes-ted fields on the stakes. The wilt fungi can grow in nutri-
ent solutions, in hoses and in watering 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 ndidcated 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. Loses 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 established and.difficult to-control.

CONTROL

Fusarium wilt should be prevented from occurring rather than treating the
problem after it exists. Hlethods of preventing or controlling Fusarium wilt are -

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

2. Obtain cutting- ,from a source that uses culture-indexed stock. Stock
is indexed (labo:_.tcry type culture) for several diseases and watched
for Fusarium w:ilt if not already included in the indexing program.
Fusarium wilt can be carried in cuttings.

3. Plant only in steLilised soil.

4. If Fusarium wilt is present,
a. Sto~iLi.?. b:I., hoses, "spaghetti" watering systems, benches
and all other equipment that comes in contact with the plants
c: pets. Flu';h out hoses am.d Twtering systems with chlorox,
LF 1C, or ot:er suitable disinfectant.

b. Keep.feet off benches, keep fingers and tools out of pots (unless
first di-ped 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. Tray 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.

CHEMOTHERAPY-HIGH LIME-ALL NITRATE NITROGEN CULTURAL CONTROL

Recent research at the University of Florida Agricultural Research and Edu-
cation Center, Bradenton, has demonstrated for the first time a method of con-
trolling 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 nitrogen fertilizer and a drench with one of the newer sys-
temic fungicides. It is important to recognize that chemical alone, or lime
alone, or proper nitrogen alone would not be expected to control Fusarium wilt,
but an integrated programmed approach using all three methods does provide con-
trol.

Where there is a history of Fusarium wilt on potted chrysanthemums, the fol-
lowing 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 pH to 7.5. In the complete fertilizer, use a nitrate form of
nitrogen (potassium, calcium or sodium nitrate) as this reduces Fusarium wilt
development. An ammonium source of nitrogen (ammonium nitrate, ammonium sul-
fate) increases the development of Fusarium wilt and also makes the pH of the
soil go down. Drench the pots with benomyl 50W fungicide. For 6" pots, use
8 ounces of a suspension containing benomyl 50W at 1/4 lb/100 gals. Apply two
times at weekly intervals after setting plants. Plants would not be expected
to recover if treated after infection occurs. 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 501, 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 are likely to develop when chrysan-
themums are grown at this high pH. However, deficiencies usually can be pre-
vented 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 phytotoxi-
city problems and they also may be added to the regular fertilizer. Iron de-
ficiency has been the most frequently encountered complication but much would
depend on the growing medium and fertilizer program being used.

The feasibility of using this chemotherapy-high lime-all nitrate nitrogen
culture regime on ground beds is being explored in current research.








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
Winter Carnival severe mild
Yellow Bonnie Jean severe none
Yellow Delaware severe none


Commercially produced plants observed with Fusarium wilt
Bonnie Jean, Deep Ridge, Delaware, Marguerite, 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 i#2 Indianapolis Bronze
Luyona
Mandalay


Maple Leaves
May Shoesmith
Mrs. Roy
Nimrod
Pinocchio
Polaris
Puritan
Showoff
Southern Sun
Statesman
Stingray
Treasure Chest
Tuneful
Yellow Knight




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