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 Symptoms
 The pathogen
 Host range and distribution
 Bibliography
 Table 2: Genera in the araceae...
 Figures






Title: Dasheen mosaic disease of araceous foliage plants
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Title: Dasheen mosaic disease of araceous foliage plants
Series Title: Plant Pathology Fact Sheet PP-42
Physical Description: Book
Language: English
Creator: Simone, G. W.
Zettler, F. W. ( Contributor )
Affiliation: University of Florida -- Florida Cooperative Extension Service -- Department of Plant Pathology -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: 199u
 Subjects
Spatial Coverage: North America -- United States of America -- Florida
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Bibliographic ID: UF00066826
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
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Resource Identifier: oclc - 51341218

Table of Contents
    Symptoms
        Page 1
    The pathogen
        Page 2
    Host range and distribution
        Page 3
    Bibliography
        Page 4
    Table 2: Genera in the araceae susceptible to dasheen mosaic virus
        Page 5
    Figures
        Page 6
Full Text



Plant Pathology Fact Sheet


Dasheen Mosaic Disease of Araceous Foliage

Plants
G. W. Simone and F. W. Zettler, Professor Retired, Extension Plant Pathologist
and Professor Plant Pathology Department, University of Florida, Gainesville,
Florida 32611
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean


The most significant viral disease affect-
ing foliage ornamentals in the nursery is
dasheen mosaic virus (DMV). Only plants in
the Araceae aroidd) family are known to sus-
tain damage from this pathogen. Much of the
importance of this disease is due to the signifi-
cance of the Araceae within the product mix of
foliage ornamentals grown nationwide. As of
the last available industry statistics, species in
the Araceae accounted for nearly 25% of U.S.
production of foliage ornamentals (4). The
Araceae contains more than 100 genera and
1,500 species of plants, including such impor-
tant foliage ornamentals as Aglaonema, Caladium,
Dieffenbachia, Epipremnum, Philodendron,
Spathiphyllum, and Syngonium. In addition to
these foliage plants, the Araceae contains the
genera Cryptocoryne (commercially grown
aquarium plant), Zantedeschia (calla lily), and
two high-carbohydrate tropical food crops
known as dasheen or taro (Colocasia) and
malanga (Xanthosoma).

Symptoms

Plant symptoms can be induced by ei-
ther an invading pathogen or an adverse envi-
ronmental or cultural factor. Symptoms in-
duced by DMV are distinct from those typically
produced by other types of pathogens infect-
ing aroids; they include leaf mosaic where the
normal leaf coloration is altered by uneven light


and dark patterns. Clearly defined ring spots
on the leaves as well as some degree of leaf dis-
tortion also occur on some hosts. A general de-
cline in plant vigor manifested by plant stunt-
ing may also occur and is more difficult to as-
sess.

Obvious symptoms in Philodendron spp.
are leaf mosaic, chlorotic streaking along veins
on leaves (Figure 1), and leaf distortion. These
symptoms are not consistent within infected
plants but may vary, with apparently healthy
foliage produced although virus infection is
still present. Reduced vigor and plant stunting
symptoms are often expressed by DMV in-
fected plants. Work in Florida (5) withPhiloden-
dron scandens oxycardium compared several cri-
teria of vigor between healthy and DMV in-
fected plants. For the growth characteristics of
leaf number, leaf area, and vine length, the dis-
eased plants sustained losses of 38.6%, 31.6%,
and 65.6%, respectively. Although virus-in-
duced foliar variegation may on occasion look
attractive, there will always be a loss of vigor
and the added risk of virus spread to other
plants.

More economic loss due to DMV infec-
tion has occurred on Dieffenbachia spp. than other
species in the Araceae. General symptoms of
DMV on Dieffenbachia spp. include leaf mosaic
(Figure 2), ringspots (Figure 3), distortion, and
stunting. Work by Chase and Zettler (1) dem-
onstrated that symptom severity varied in


PP-42







Florida with time of year. The most severe
symptoms developed between July and Sep-
tember and between November and January.
Species and cultivars of Dieffenbachia also dif-
fered in severity of symptom expression (1). Of
eight species and/or cultivars tested, disease
reactions to DMV fit into categories based upon
initial (acute) symptom development and long
term (chronic) symptom development (see
Table 1). Two varieties had severe initial symp-
toms that progressed to plant death, thus elimi-
nating infected plants from production. The
majority of varieties examined had severe early
symptoms but either mild or no symptoms in
subsequent growth; thus, marketability was not
greatly affected. Both D. maculata "Perfection"
and "Lemon" expressed moderate initial reac-
tions to disease but these worsened at certain
times during a production cycle point that se-
riously impaired marketability. For these two
varieties, avoiding DMV infections is based on
acquisition and maintenance of virus-free, tis-
sue-cultured stock to support their production.

As with Philodendron oxycardium, DMV-
infected Dieffenbachia sustained considerable
loss in plant vigor. Using a virus-free, tissue-
cultured D. maculata "Perfection 137B" line, re-
searchers compared healthy and virus-infected
plants under the same growing conditions (2).
Virus-free plants out-yielded infected plants by
producing 25.3 cuttings per plant compared to
9.1 cuttings for diseased stock. These same
plants were subjected to a visual rating for dis-
ease symptoms on a scale of 1 to 4 where a rat-
ing of 1 indicated no symptoms and complete
salability while a rating of 4 indicated severe
symptoms and an unsalable condition. Virus-
free stock rated 1.01; infected stock rated 3.27.
The superiority of virus-free stock has also been
demonstrated for Caladium hortulanum (Figure
4), in terms of leaf area, tuber weight and num-
bers of tubers produced when compared with
infected stock (3).


The Pathogen

Viral pathogens like DMV are relatively
small and simple compared to fungal and bac-
terial pathogens. Individual DMV particles are
observable only by electron microscopy. In fact,
it would take 600 or more particles laid end-to-
end to span the width of one pencil point. In
addition to their small size, DMW particles are
simple entities, consisting only of a strand of
nucleic acid surrounded by a protein coat that
functions as an obligate parasite in the plant
host. The virus is totally dependent upon the
physiological machinery of the plant cell to
duplicate and spread within the plant.

Disease Spread

Unlike fungal and bacterial pathogens,
viruses have a significant dependence on other
organisms (vectors) to facilitate their movement
in the environment from plant to plant. In the
case of DMV, winged aphids have been dem-
onstrated to transmit this virus in a non-persis-
tent manner to susceptible plants. Several aphid
species have been shown to be effective vec-
tors of DMV including the green peach aphid
(Myzus persicae), the cotton-melon aphid (Aphis
gossypii), and the cowpea aphid (Aphis
craccivora). These aphids will probe infected
plants with their feeding spears or stylets. In
less than 1 minute, these aphids pick up virus
particles on the ends of their stylets, after which
they can fly to another suitable host plant and
transmit the DMV particles.

The activity of the grower is also impor-
tant in the spread of DMV. Most Araceous foli-
age species are vegetatively propagated for two
very good reasons. Many ornamental aroid spe-
cies do not flower and set seed readily under
nursery production conditions. When they do,
the seedlings do not breed true to parental
types. Although seed production is an effective
means to eliminate DMV from a plant type (the
virus is not seedborne), seedling progeny are
variable and seldom meet the horticultural stan-







dard of the foliage industry. Hence, the use of
tip or eye cuttings, cane cuttings, or tuber divi-
sions to rapidly and economically propagate
desired aroid foliage plants is preferred over
seed propagation. Although vegetative propa-
gation does meet the market demands for plant
production, it also can effectively increase inci-
dence of such systemic plant pathogens as
DMV. Infected stock plants usually give rise to
infected propagules and, in the process of
propagation itself, infected plant sap on a
propagation knife could transmit DMV to a
previously healthy plant during the cutting
operation.

Host Range and Distribution

Dasheen mosaic was first documented
by researchers in Florida (7) in 1970. Samples
of Aglaonema, Caladium, Colocasia, Dieffenbachia,
and Xanthosoma were found to be naturally in-
fected with a flexuous rod-shaped virus. Sub-
sequent investigations (6) have expanded the
susceptible host range for DMV to include 13
genera in the Araceae family (see Table 2). DMV
world wide is known to occur on the five major
continents (6). A few economically important
foliage plants in the Araceae have not been
demonstrated to be susceptible to DW at this
time. These include Epipremnum aureum
(Golden Pothos), Scindapsus pictus (Satin
Pothos), and Syngonium spp. (Arrowhead-Vine).

Diagnosis

Plant symptoms are the critical first step
in viral disease determination; however, the
variability in symptom expression of infected
plants may make additional techniques neces-
sary for accurate determinations of DMV in
stock or production areas. Direct examination
of infected plant sap by electron microscopy
will reveal viral particles that can confirm the
presence of this virus. Two more available tech-
niques include serology and plant virus inclu-
sion-body staining. Diagnostic facilities differ
as to which techniques they employ but the


aforementioned techniques are rapid and avail-
able in many laboratories.

Control

An integrated effort should be used to
develop a control program for DMV. The rapid
transmission of the virus by aphid vectors
makes use of conventional insecticides ineffec-
tive in situations where aphids are already
present. In addition, there are no effective pre-
ventative or eradicative pesticides to deal with
viral diseases at this time. Only rigid cultural
controls will allow satisfactory control of DMV
problems on particular aroids.

Table 1. Varietal Reaction of Dieffenbachia
spp.to Dasheen Mosaic Virus'.
Moderate
Moderate Severe Acute Severe Acute
Chronic Mild Chronic Death
Chronic
(D. maculata)
(D. maculata) .(D. x memoria-
(D. aculata) "Rudolph
"Perfection" Rohcorsii
Roehrs"

(D. amoena)
"Tropic Snow"

1Research reported by Chase,A.R. and F.W.
Zettler 1982. PLant Disease 66:891-893.


The following control observations are
made in an effort to limit introduction and
spread of DMV in the nursery.

1. Control Araceous and other weed species
either within or outside production areas that
can serve as a virus and/or aphid vector reser-
voir.

2. Maintain adequate insect control especially
in greenhouses, to avoid buildups of potential
aphid vectors of DMV.

3. Aroids propagated extensively by seed (e.g.
Philodendron selloum and some Spathiphyllum







spp.) can be expected to have few DMV prob-
lems since the virus is not seedborne.

4. The majority of aroids propagated vegeta-
tively must begin with the highest quality,
pathogen-free stock that can be obtained. A
number of tissue-culture companies can be con-
tacted for direct purchase of pathogen-free
plants or for contracted production of special
material.

5. DMV-free stock blocks should be isolated
from production areas and must be inspected
routinely for DMV symptoms throughout the
year, since symptom expression varies with the
tinie ofyear and species affected.

6. Replace all plants exhibiting virus symptoms
and replace with DMV-free stock whenever
possible. DMV is systemic and cannot be cured.
smn e cltivars Dieffenbachia amoena and Chi-
nese evergreen), although diseased, are still
commercially valuable.

7. Choose a procedure for propagation that pre-
vents introduction and spread of DMV and
other pathogens in the stock block:

a) Limit use of propagation tools to one culti-
var or stock block at a time.

b) Propagation tools should be changed or
disinfested prior to reuse with other stock
blocks as insurance against virus spread.

8. Remove accumulated plant sap or pieces of
plant tissue that become lodged within or on
scissor or anvil-type shears prior to dipping.

9. Dip tools in a saturated solution of trisodium
phosphate (TSP) for at least 15 to 20 seconds.
Rinse tools in water after dipping in TSP. Dis-
card the solution as soon as it begins to dis-
color.

10. Stock blocks produced from tissue-cultured
plants are initially pathogen-free but are not


pathogen protected. The practical life span of a
stock block depends on the level of sanitation
maintained by the individual grower.

Literature Cited

1. Chase, A. R. and F. W. Zettler. 1982. Dasheen
mosaic virus infection ofdieffenbachia cultivars. Plant
Disease 66:891-893.

2. Chase, A. R., F. W. Zettler, and J. F. Knauss.
1981. Perfection 137B: A Pathogen-free selection of
Dieffenbachia maculata derived through tissue cul-
ture. Circular S-280. FL. Ag. Exp. Sta., I.F.A.S.,
Univ. of FL., Gainesville, 8p.

3. Hartman, R. D. and F. W. Zettler. 1974. Effects
of dasheen mosaic virus on yields of caladium,
dieffenbachia, and philodendron. Phytopathology
64:768.

4. U. S. Bureau of the Census. 1974. U. S. Cen-
sus of Agriculture Vol. V. Special Reports, Part
1. Horticulture Specialties. Washington D.C.: U.
S. Government Printing Office.

5. Wisler, G. C., F. W. Zettler, R. D. Hartman,
and J. J. McRitchie. 1978. Dasheen mosaic virus
infections of philodendrons in Florida. Proc. Fla.
State Hort. Soc. 91:237-240.

6. Zettler, F. W., M. M. Abo El-Nil, and R. D.
Hartman. 1978. Plant Virus Description No. 191.
Commonwealth Mycological Institute, Ferry
Lane, Kew, Surrey, England. 4 pp.

7. Zettler, F. W., and R. D. Hartman. 1987.
Dasheen mosaic virus as a pathogen of cultivated
aroids and control of the virus by tissue culture.
Plant Disease 71:958-963.










Table 2. Genera in the Araceae Susceptible to Dasheen Mosaic Virus.


Economic
Genus Common Name
Importance

Aglanom ea Chinese evergreen Foliage ornamental

F o liage
E lephant's-ear F l
A locasia ornamental, food
p lant
crop

F o liage
Amorphophallus Devil's tongue ornamental, food
crop

F lowering
Anthurium Flamingo lily
ornamental

A r m a Dragon root,
A risaem a W ild flower
Jack-in-the-Pulpit

Caladium Caladium Foliage ornamental

SFood crop, foliage
Co locasia Dasheen, taro
ornamental

Cryptocoryne C rypts Aquarium plant

Cyrtospermia Food crop

Dieffenbachia Dumb cane Foliage ornamental

Philodendron Philodendron Foliage ornamental

Spathiphyllum Peace lily Foliage ornamental

X t M alanga, Food crop, foliage
Xanthosoma
cocoyam ornamental

F lowering
Zantedeschia C alla lily
ornamental


























Figure 1. Chlorotic streaking along leaf veins
of Philodendron scandens oxycardiurn
caused by DMV.


Figure 3. Ringspot symptoms in
Dieffenbachia maculata "Rudolph Roehrs".


Figure 2. Leaf mosaic and distortion symp-
toms on Dieffenbachia "Exotica" cultivar
caused by DMV. (Contrast with healthy leaf
on left.)


Figure 4. Natural variegation (upperleaf) and
DMV symptoms (lower leaf) in Caladium
hortulanum "Candidum.




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