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 Copyright
 Symptoms
 Causal factors
 Conditions favoring disease...
 YSL experiments
 Control recommendations






Group Title: Research report - Bradenton Agricultural Research & Education Center - GC-1974-7
Title: Etiology and control of the yellow strapleaf disease of chrysanthemum
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
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Permanent Link: http://ufdc.ufl.edu/UF00067687/00001
 Material Information
Title: Etiology and control of the yellow strapleaf disease of chrysanthemum
Series Title: Bradenton AREC research report
Physical Description: 5 leaves : ; 28 cm.
Language: English
Creator: 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: 1974
 Subjects
Subject: Chrysanthemums -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: S.S. Woltz
General Note: Caption title.
General Note: "April, 1974."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00067687
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 - 71843148

Table of Contents
    Copyright
        Copyright
    Symptoms
        Page 1
    Causal factors
        Page 2
    Conditions favoring disease development
        Page 2
    YSL experiments
        Page 3
    Control recommendations
        Page 4
        Page 5
Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida





AGRICULTURAL RESEARCH & EDUCATION CENTER
fitJ) IFAS, University of Florida
Bradenton, Florida

Bradenton AREC Research Report GC-1974-7 April, 1974
-1
ETIOLOGY AND CONTROL OF THE YELLOW STRAPLEAF DISEASE OF CHRYSANTHEMUM

S. S. Woltz
Plant Physiologist


The yellow strapleaf diseaSq Y observed in all major chrysanthemum
growing areas of the state r ilitcL t if past 20 years since this
floral crop has been grown n a significai A drc al scale. In a survey of
the commercial plantings i Florida in 1958, the di ease was found in almost
every large commercial pla ting. Z sa fivsh 10D per ent of the plants in any single
planting were affected, an in most cases er th n 0.1 percent were found.
incidence of the disease hLgenerally declined ov r the years apparently asso-
ciated with adoption of p jeStye tural techn ues by growers. There have
recently been several serious M Of furring. Since the disease is
difficult to predict and since incidence more widespread in the future
than previously experienced, it is desirable to assess the present state of
knowledge about YSL and fill in missing parts of the cause and control picture.

Symptoms

The name yellow strapleaf was selected because pale yellow, narrow leaves are
noticeable symptoms of the disease. The disease commonly appears 3-4 weeks
after planting and most often after pinching if the crop is pinched. First
symptoms are usually seen in young developing leaves in axillary shoots (pinched
crop) or terminal shoots (unpinched crop). These leaves fail to expand normally,
becoming claw-shaped with upward rolling of margins and incurved tips. Pinching
seems to cause the symptoms to develop more quickly and uniformly. As the narrow,
pale yellow leaves slowly expand, they begin to flatten out and assume a dull
yellow or ivory color. At this stage leaves are frequently narrow, very much
elongated, and slightly brittle with small lobes, serrations or entire margins.
A characteristic symptom is the severe retardation of new growth after pinching.
Axillary buds turn yellow and may be slightly swollen. New leaves open very
slowly and internodes are short. The upper portion of the stems of affected
plants are often slightly larger in diameter and the entire stem becomes abnor-
mally hard and brittle. Symptoms are similar for various commercial cultivars.
The disease has been noted in 20 or more cultivars, but is seen most often in
Iceberg, Blue Chip and Shasta. The disease may occur in plants at later stages
including plants on which flower buds are visible. The symptoms are sufficiently
different from those of other diseases to simplify identification.

In severe cases diseased plants may remain stunted and yellow for 6 to 8 weeks
during which time they only grow 4 to 6 inches., Root development is normal and
may be slightly greater in diseased plants. Stunted plants often resume normal
growth after a period of time. Leaves which are already strap-shaped never de-
velop normal shapes but yellow tissues turn green and new growth may be normal
except for a residual stunting. Flowers produced on recovering plants are fre-
quently small and distorted with few expanded ray petals. The centers of heads
are abnormally compact and green partly due to excessive growth of involucral
bracts around the disc flowers.








Causal Factors

The specific cause of YSL has not been determined; the general nature of contribu-
ting factors has, however, been delineated. Accumulated information strongly
suggests that YSL is caused by an amino acid toxin released in the soil by one
or more soil microorganisms. The toxin disrupts amino acid metabolism within
the plant after being accumulated from the soil. While there is no indication
that the organism directly invades chrysanthemum plants in producing disease,
there is indication that disease may be prevented by controlling the population
of soil microorganisms.

A common soil-inhabiting fungus, Aspergillus wentii has been shown to produce the
YSL symptoms but a cause-effect relationship has not yet been established impli-
cating this species with YSL in the field. The disease is unique in that the
symptoms can be produced either with or without the presence of living A. wentii
cells when the toxin is present in the root zone of chrysanthemum plants. The
toxin could be produced, for example, in the subsoil and then transported upward
with capillary water movement into the root zone; or soil could be steamed and
residual toxin could cause the disease to develop in cuttings planted after
steaming. The toxin produced by A. wentii is l-amino-2-nitro-cyclopentane-l-
carboxylic acid (ANCPA), an antagonist of leucine in amino acid metabolism.
Research is in progress to identify the causal microorganisms) with the knowledge
that more than one organism and also more than one toxin may produce YSL.

Conditions Favoring Disease Development

In Florida, YSL appearance is usually associated with warm weather, roughly April
to November. High rainfall and ample irrigation together with soil conditions
favoring retention of soil moisture and reduced areation all contribute to develop-
ment of the disease which is usually found in the lower parts of a planting. The
difference in elevation may be very slight but the soil surface condition will
indicate higher moisture conditions in terms of darkness of color, cohesiveness
of soil and presence of algae or fungi growing on the soil surface. The mainte-
nance of seep-water level that is optimum or slightly high for most beds may
saturate the root zone soil in low areas. In potted greenhouse plants growing
in soil from around YSL plants, the disease developed much more readily in plastic
pots kept wet than in clay pots. The difference appears to be due to a lower
degree of aeration and greater moisture retention in plastic pots.

YSL occurrence has been observed to be less with steaming of foil cc.mpared with
various methods of fumigation. When entire plantings are steamed, there is
usually a low incidence of YSL; occasional plants may have YSL, however, when
non-sterilized subsoil is brought up to the soil surface in digging post holes.
Another indication of the effects of contamination of soil microorganisms is the
occasional observation that surface flooding by heavy rain-s nany cause a widespread
and randomly distributed occurrence of YSL apparently associated with an influ::
of soil microorganisms under conditions favoring disease development.

In addition to the observed occurrences of YSL on both the east and west coasts
of central to south Florida, it was found in plantings in St. Johns County for a
number of consecutive years. Reports from Georgia, Massachusetts, Now York,
North Carolina and Republic of Panama indicate the occurrence of YSL in those
areas, verified by persons familiar with the symptoms. The report from New York
(Long Island) was of special interest since it constituted the single observance
of YSL in commercial pot plant production, involving about 1000 pots. While YSL








Causal Factors

The specific cause of YSL has not been determined; the general nature of contribu-
ting factors has, however, been delineated. Accumulated information strongly
suggests that YSL is caused by an amino acid toxin released in the soil by one
or more soil microorganisms. The toxin disrupts amino acid metabolism within
the plant after being accumulated from the soil. While there is no indication
that the organism directly invades chrysanthemum plants in producing disease,
there is indication that disease may be prevented by controlling the population
of soil microorganisms.

A common soil-inhabiting fungus, Aspergillus wentii has been shown to produce the
YSL symptoms but a cause-effect relationship has not yet been established impli-
cating this species with YSL in the field. The disease is unique in that the
symptoms can be produced either with or without the presence of living A. wentii
cells when the toxin is present in the root zone of chrysanthemum plants. The
toxin could be produced, for example, in the subsoil and then transported upward
with capillary water movement into the root zone; or soil could be steamed and
residual toxin could cause the disease to develop in cuttings planted after
steaming. The toxin produced by A. wentii is l-amino-2-nitro-cyclopentane-l-
carboxylic acid (ANCPA), an antagonist of leucine in amino acid metabolism.
Research is in progress to identify the causal microorganisms) with the knowledge
that more than one organism and also more than one toxin may produce YSL.

Conditions Favoring Disease Development

In Florida, YSL appearance is usually associated with warm weather, roughly April
to November. High rainfall and ample irrigation together with soil conditions
favoring retention of soil moisture and reduced areation all contribute to develop-
ment of the disease which is usually found in the lower parts of a planting. The
difference in elevation may be very slight but the soil surface condition will
indicate higher moisture conditions in terms of darkness of color, cohesiveness
of soil and presence of algae or fungi growing on the soil surface. The mainte-
nance of seep-water level that is optimum or slightly high for most beds may
saturate the root zone soil in low areas. In potted greenhouse plants growing
in soil from around YSL plants, the disease developed much more readily in plastic
pots kept wet than in clay pots. The difference appears to be due to a lower
degree of aeration and greater moisture retention in plastic pots.

YSL occurrence has been observed to be less with steaming of foil cc.mpared with
various methods of fumigation. When entire plantings are steamed, there is
usually a low incidence of YSL; occasional plants may have YSL, however, when
non-sterilized subsoil is brought up to the soil surface in digging post holes.
Another indication of the effects of contamination of soil microorganisms is the
occasional observation that surface flooding by heavy rain-s nany cause a widespread
and randomly distributed occurrence of YSL apparently associated with an influ::
of soil microorganisms under conditions favoring disease development.

In addition to the observed occurrences of YSL on both the east and west coasts
of central to south Florida, it was found in plantings in St. Johns County for a
number of consecutive years. Reports from Georgia, Massachusetts, Now York,
North Carolina and Republic of Panama indicate the occurrence of YSL in those
areas, verified by persons familiar with the symptoms. The report from New York
(Long Island) was of special interest since it constituted the single observance
of YSL in commercial pot plant production, involving about 1000 pots. While YSL








can be induced in potted chrysanthemums and pot varieties, the cultural procedures
used in growing potted chrysanthemums do not favor YSL; the common pot varieties
which do not grow to a large size appear less susceptible to YSL than other
varieties.

YSL Experiments

Exploratory research was carried out with the object of developing leads to the
cause and control of YSL. Herbicides and viruses were studied as possible causes
and ruled out. Simple inoculation and grafting procedures indicated the disease
was not directly transmissable in terms of an infectious disease. Thallium
toxicity, studied with the similar disease frenching of tobacco, did not produce
YSL in chrysanthemums.

Complete soil and plant chemical analyses did not reveal any abnormal nutritional
situation in paired YSL-no YSL samples from various areas of the state. Complete
nutrient solutions of known inorganic nutrients did not correct severe YSL in
the field when used repeatedly as combination spray-drench treatments. Indivi-
dual micronutrients (boron, copper, iron, manganese, molybdenum and zinc) were
tested similarly without evidence of marked improvement. Although deficiencies
of nutrients do not appear to be the basic cause of YSL, the development of the
disease is subject to the effects of many soil-nutritional and environmental
factors. This is not unexpected in view of the complexity of a disease situation
with soil-plant-microorganism interactions.

A field experiment conducted in late summer of 1959 at the Cortez farm of the then
Gulf Coast Experiment Station fortunately had a significant incidence of YSL asso-
ciated with cultural variables included to favor or control YSL. The results,
while insufficiently uniform to analyze statistically, indicated a doubling of
the incidence of YSL due to an inoculation of halves of plots with a slurry of
YSL inducing soil from a commercial planting (41 vs. 20 YSL plants). An amend-
ment of soil with wood shavings increased YSL 3-4 fold over two rates of German
peat and a no-conditioner treatment. Wood as a source of energy for pathogen
or general soil microorganisms could stimulate toxin production or cause a
lowered availability of nitrogen to chrysanthemum plants, either of which would
increase YSL. Sixteen randomized control plots (ammonium nitrate + potassium
nitrate) had no YSL; 16 plots receiving Peruvian guano supplementally had 19
YSL plants. Comparable data for sewage sludge, slaughterhouse tankage and castor
pomace were 6, 10 and 12 YSL plants, respectively. Thus, it is indicated that
certain organic nitrogen sources are likely to increase YSL.

YSL occurred throughout an experiment in a late summer planting with the results
as shown in Table i. .

The following interpretation is made of these results in light of other experi-
ments with chrysanthemums and also in view of the accumulated knowledge with
frenching of tobacco, a similar disorder. The low level of nitrogen probably
did not permit the plants to alleviate soil toxin effects by internal amino
acid production, as indicated by 142 YSL plants at the half-pound nitrogen rate
in comparison with 64 affected plants with the one-pound rate. Also, the slowly
available urea-formaldehyde fertilizer (#5) may have supplied a lower level of
nitrogen producing an effect similar to low-level nitrogen nutrition. Treatment
No. 2, ammonium and calcium nitrate, may have favorably influenced microbial
activity and toxin production by producing higher soil pH levels than the acid-
forming treatments, urea (Nos. 3 and 4) and ammonium nitrate (No. 1).





-4-


There is evidence that iron applied to the soil as ferrous sulfate at very high
levels (300 lbs/a) hastens recovery from YSL but that this is not related to iron
nutrition of the plants since YSL plants did not respond to foliar iron. Rather,
indications are that the soil microbial environment is significantly altered by
ferrous sulfate since it lowers pH and also temporarily provides soluble iron in
the coil solution.

An unusual procedure was evaluated in looking for control methods for YSL, namely
that of lifting the plant root ball and replanting in the same location. This
was tested because efforts to lift and replant into pots in the greenhouse fre-
quently resulted in a disappearance of YSL. Experiments including this procedure
under varying field conditions have met with results ranging from highly success-
ful (95% of plants recovered) to little success. The results appeared related
to the stage of the disease and soil conditions. Early stages of moderate disease
in soil of good tilth were benefited considerably by lifting. More advanced
stages in terms of time of onset of symptoms and more severely diseased plants
did not recover as readily. The beneficial effects of lifting plants appear to
be associated with aeration of soil and slight root pruning. Aeration appears
to restore a soil microbial environment unfavorable to toxin production by
pathogens. Root pruning and disturbance of the root system probably interfere
uith continued uptake of toxin.


Table 1. Effect of weekly nitrogen applications on incidence of yellow strapleaf


No. YSL plants
Treatment Nitrogen 1/2 lb Nitrogen 1 lb :ii-ogen
no. source per 100 sq ft per 100 sq ft Total

1 Ammonium nitrate 25 12 37
2 Half ar.onium,
half calcium nitrate 40 11 51
3 Urea 25 7 32
4 Urea, ammonium phosphate 15 7 22
5 Urea-formaldehyde
s.lc--ly available 37 27 64

Total 142 64



Control Recommendations

1. In steaming or fumigating soils, follow recommended practices:
a. Treat uniformly all areas to be planted or bedded.
b. AoJid contamination of prepared planting sites with non-pasteurized soil
s in digging post holes.
c. Avoid reccntamination from untreated areas, conditioners and tools.

2. Provide dikes and surface drainage so that heavy rains do not cause flooding
from .tret e~ areas; alno, provide good internal drainage and soil aeration.
Avoid soil.- that "run together."








3. Avoid soil conditioners which break down readily to render soil less
permeable to water and air and which may support increased microbial
activity. If only inferior conditioners are available, consider
omitting amendment.

4. Do not use organic nitrogen materials which would support growth of
bacteria and fungi.

5. Maintain adequate levels of nitrogen nutrition with adjustments for
leaching losses and plant growth rate.

6. As a provisional procedure (see YSL Experiments), lift YSL-affected
plants and reset in the same spaces after it is apparent that the
disease is likely to be a production problem but before the con-
dition becomes too advanced. Do not employ this procedure when
plants are too large and growing conditions are too dry to permit
plants to continue essentially normal growth after lifting and
replanting.




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