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 Anthracnose
 Table 1: Susceptibility of fruit...
 Powdery mildew
 Stem-end rot
 Figures






Title: Some common diseases of mango in Florida
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Permanent Link: http://ufdc.ufl.edu/UF00066887/00001
 Material Information
Title: Some common diseases of mango in Florida
Series Title: Plant Pathology Fact Sheet PP-23
Physical Description: Book
Language: English
Creator: Pernezny, Ken
Ploetz, Randy
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: 1988
 Subjects
Spatial Coverage: North America -- United States of America -- Florida
 Record Information
Bibliographic ID: UF00066887
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.
Resource Identifier: oclc - 51340611

Table of Contents
    Anthracnose
        Page 1
    Table 1: Susceptibility of fruit of different mango cultivars to anthracnose bacterial spot
        Page 2
    Powdery mildew
        Page 3
    Stem-end rot
        Page 4
    Figures
        Page 5
        Page 6
        Page 7
Full Text



Plant Pathology Fact Sheet


Some Common Diseases of Mango in Florida

Ken Pernezny and Randy Ploetz, Professor of Plant Pathology, Everglades Re-
search & Education Center, Belle Glade, Fl 33430; and Professor of Plant Pathol-
ogy, Tropical Research and Education Center, Homestead,Fl 33031 University of
Florida, 1988, Revised March 2000.
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Christine Waddill, Dean


The mango (Mangifera indica), produces
a tree fruit well-known and widely consumed
throughout the tropical world. Demand for
mangoes is increasing in Florida as more
people become aware of its unique flavor and
as the Latin American population grows.

The number of diseases affecting mango
in Florida is relatively small but can seriously
limit production if not adequately controlled.
This fact sheet concentrates on the symptoms
of the important mango diseases, the weather
conditions conducive to disease development,
and methods for control. Due to frequent
changes in the availability and use restrictions
for agricultural chemicals, consult the Univer-
sity of Florida Extension Service for specific,
current fungicide recommendations.

Anthracnose

Anthracnose, the most important mango
disease, is caused by the fungus Colletotrichum
gleosporioides. Flower blight, fruit rot, and leaf
spots are among the symptoms of this disease.
Symptoms on the panicles (flower clusters) start
as small black or dark-brown spots. These can
enlarge, coalesce and kill the flowers (Fig. 1),
greatly reducing yield.

On leaves anthracnose lesions start as
small, angular, brown to black spots (Fig. 2). If


tissue is young when originally infected, spots
can enlarge to form extensive dead areas (Fig.
2). Lesions that begin in older leaves are usu-
ally smaller with a maximum diameter of 1/2
inch (6 mm); they appear as glossy dark brown
to black angular spots.
Fruit infection commonly occurs and can re-
sult in serious decay problems in the orchard,
in transit, at the market, and after sale. The fun-
gus invades the skin of fruit and remains in a
"latent" (a living but nonsymptom-producing)
state until fruit ripening begins. Ripe fruit, ei-
ther before or after picking, can then develop
prominent dark-brown to black decay spots
(Fig. 3). These may coalesce and can eventu-
ally penetrate deep into fruit, resulting in ex-
tensive fruit rotting. An interesting manifesta-
tion of anthracnose fruit damage is the symp-
tom called "tear staining" (Fig. 4) that devel-
ops when spore-laden water droplets from in-
fected twigs and panicles wash over and infect
the fruit.

Anthracnose is usually more serious in
years when rain and heavy dews are frequent,
from the onset of flowering until fruit are about
half size.

Control of anthracnose, especially on
very susceptible cultivars, such as 'Haden' and
'Irwin', centers on a diligent fungicide program.
Effective control of even the postharvest phase
of this disease is best accomplished by a good
spray program in the orchard. Begin fungicide


PP-23








applications at the first appearance of panicles
and continue spraying at recommended inter-
vals until the pre-harvest waiting period is
reached.


Homeowners may want to consider planting
moderately resistant cultivars, such as Carrie,
Edward, or Glenn to minimize the need for ex-
tensive spraying.


Table 1. Susceptibility of fruti of different mango cultivars to anthracnose and bacterial spot.


Disease reaction

Cultivar Anthracnose Bacterial black spot


Carrie MR R

Earlygold MR R

Edward MR HS

Fascell S S

Florigon MR HS

Glenn MR S

Haden S HS

Irwin HS S

Julie MR

Keitt MR HS

Kent HS HS

Man dok Mai R

Palmer S

Sensation S HR

Tommy Atkins MR S

Van Dyke MR R

Zill S S


zDisease reaction: HR= highly resistant; R=resistant; MR=moderately resistant; S= suscep-
tible; and HS= highly susceptible








Powdery Mildew


Powdery mildew is caused by the fun-
gus Oidium mangiferae. Although a somewhat
sporadic disease, it can cause severe crop loss
due to flower and panicle infection and subse-
quent failure of fruit set.

The diagnostic key in the identification
of this disease is the appearance of a whitish,
powdery growth of the fungus on panicles and
young fruit. Young infected fruit turn brown
and fall. The white growth can also be seen on
the undersurface of young infected leaves. Se-
vere infection of young leaves results in pre-
mature leaf drop. On mature leaves, the spots
turn purplish brown, as the white fungal mass
eventually disappears (Fig. 5).

Powdery mildew occurs in the spring-
and is particularly destructive in years when
the weather is cool and dry. Control is fungi-
cide treatment.

Alga Spot
(Red Rust, Green Scurf)

A parasitic alga, Cephaleuros virescens,
incites this relatively minor disease of mango.
Leaf spots start as circular green-gray areas that
eventually turn rust red as the alga produces a
profusion of rust-colored microscopic "spores"
on the leaf surface (Fig. 6). Infection of stem tis-
sue can also occur and is much more serious
than leaf infection. Cankers develop in the bark
and stem-thickening can take place at infection
sites. Rust-red "spore" masses will also de-
velop on infected stems. Severely diseased
branches may have to be pruned from the tree.
Alga spot only becomes a serious problem
when growers are overly dependent on organic
fungicides for general foliar disease control. It
normally is not a problem where copper fungi-
cides are used periodically.


Verticillium wilt, caused by the soil-
borne fungus Verticillium albo-atrum or V. dahliae
is a disease of increasing importance to mango
production, especially on the Rockdale soils of
Dade County. The problem is usually observed
in young trees planted on land previously
cropped to vegetables that are also susceptible
to this disease. The Verticillium fungus can
survive in soil in a dormant state for at least 15
years. When trees are set in infested soil, the
fungus returns to an active stage and invades
the mango roots. As Verticillium colonizes and
blocks the vascular (water-conducting) system,
trees begin to exhibit symptoms of water stress.

Trees decline and die back slowly in a
more or less random fashion in the grove.
Leaves wilt and die, often in a characteristic
"one-sided" fashion, a key diagnostic feature
(Fig. 7). The dead leaves often remain attached
to infected branches, giving the tree a "fired"
appearance (Fig. 7). If longitudinal cuts are
made in infected branches, brown vascular dis-
coloration is often evident.

The only practical control for this disease
is to avoid agricultural land with a previous
history of intensive vegetable production. Un-
fortunately, management of Verticillium wilt
through site selection is becoming more diffi-
cult in areas of increasing urbanization.

Mango Decline

Several different diseases of mango, in-
cluding blight, canker, gummosis, twig blight,
tip die-back and stem bleeding, are listed here
under the general term decline. Although these
diseases are caused by several different fungi,
notably C. gleosporiodes, Dothiorella spp. and
Lasiodiplodia theobromae, they are all capable of
causing all or some of the following symptoms:
marginal scorching of leaf lamina which may
or may not progress to defoliation; foliar symp-


Verticillium Wilt







toms of nutritional deficiencies -particularly of
iron and manganese; dieback of small branches
basipetally from the terminal (Fig.8); oozing of
a clear or cloudy exudate, either from terminal
buds or from branches, scaffold limbs or trunks
(Fig.9); and vascular discoloration. The causal
fungi are endophytes in mango (infect, but do
not necessarily cause symptoms), many of
which also cause stem-end rots on fruit.

The internal location and the diversity
of fungi that are involved in the decline syn-
drome reduce the opportunities for controlling
these disorders with fungicides. These prob-
lems are usually observed after trees are af-
fected by cold weather, drought, poor fertility
and other stress factors. Thus, management of
the controllable predisposing factors is benefi-
cial.


Stem-end Rot

Stem-end rot is usually a post-harvest
disease of mango fruit. It can be important, es-
pecially when anthracnose, the most important
post-harvest problem on fruit, is well con-
trolled. In general, the stem-ends of affected
fruit appear dark brown and watersoaked, and
the affected areas may extend internally well
into the fruit.

Stem-end rot is caused by many of the
same fungi that cause mango decline, in par-
ticular C gleosporiodes, Dothiorella spp. and L.
theobromae. "De-sapping" (placing the stem end
of newly harvested fruit into the soil or turf
beneath trees) should be avoided since infec-
tion by L. theobromae can be promoted by this
practice. Post-harvest treatment of fruit with hot
water or fungicides can reduce the develop-
ment of this disease.


Malformation

Malformation is a destructive disease
that has been recognized in southern Florida
since the early 1970s. Fortunately, malforma-
tion is more damaging in regions of the world,
such as India and Pakistan, than in areas with
appreciable rainfall, such as southern Florida.

Malformation affects vegetative and flo-
ral tissues of mango. Apical or axillary buds
produce misshapen shoots with shortened in-
ternodes and dwarfed leaves which are brittle
and recurve towards the supporting stem.
Shoots may not expand fully, resulting in a
bunched appearance on these portions of the
plant. For these reasons, the disease can be quite
important in nurseries. More important, how-
ever, is the affect of malformation on fruit set:
fruit in affected panicles either do not set or
abort. Primary and secondary axes on affected
panicles are shortened, thickened and greatly
branched. Malformed panicles may produce as
many as three times the normal number of flow-
ers, and these are usually enlarged. Inflores-
cences may also have an increased proportion
of male vs. perfect flowers and may produce
dwarfed and distorted leaves (exhibit phyllody)
(Fig.10).

The fungusFusarium subglutinans causes
malformation. It is believed that the mango bud
mite, Eriophyes mangiferae, is a vector of this
pathogen that enhances infection by wounding
host tissues while feeding on mango. The
pathogen is spread by grafting and in infected
nursery stock. Unfortunately, no effective fun-
gicides exist for the control of this disease. Pri-
mary emphases should be placed on using
pathogen-free propagation materials when new
orchards are established. If the disease is
present in an orchard, all symptomatic tissues
plus the subtending three nodes should be re-
moved from the orchard and burned.


























h.


Figure 1. Severe anthracnose infection of mango panicle (flower cluster, left) compared to
near disease-free panicle (right).


Figure 2. Anthracnose infections in mango
leaf. Note coalescence of lesions along mid-
rib.


Figure 3. Numerous circular areas of anthra-
cnose damage in mango fruit.





























Figure 4. The "tear-staining" symptom some-
times associated with anthracnose on mango
fruit.


Figure 6. Alga spot in mango leaf. The alga is
at the stage where it is producing great
masses of red "spores" on the leaf surface.


Figure 5. Late-state powdery mildew infec-
tion on underside of mango leaf.


Figure 7. Verticillium wilt of young mango
tree.


































Figure 8. Mango decline: tip dieback and
branch death in a young tree.


Figure 9. Mango decline: gummosis symp-
tom of decline in a young tree.


Figure 10. A malformed mango panicle in
which leaves have developed, a typical
symptom.




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