Mango diseases and
their management
M. Mithal
Jiskani,
Assistant Professor,
Department of Plant Pathology,
Sindh Agriculture University, Tandojam
Mango, Mangifera indica L. is one of the most important
foreign currencies earning fruit crop of Pakistan, through
exporting to many countries, mainly to Dubai, Saudi Arabia,
UK, Germany, France, Holland, Switzerland, Italy, Singapore
and Malaysia. It is known as the “King of fruits”, because the
mango fruit is nutritionally rich in carbohydrates and vitamin
A and C. It is relished and liked by every one for its flavour
and dietetic value and is also claimed to be of medicinal
value. For instance, chutney made from the green (unripe)
fruit is considered to be an effective antidote for mild forms
of sunstroke. Apart from this, unique mango recipe such as
mango ice cream, mango milk shakes, mango squashes etc. are
favourite desserts. Mango juice, jelly, marmalade, pickles
etc. are also commonly consumed.
Pakistan offers a wide choice of near about 200 mango
varieties. Some of the most famous varieties are Sindhri,
Dusheri, Summer Behist Chaunsa, Anwar Ratole and Langra. These
varieties were released from 1949 to 1967, with yield
potential of 8000 to 21600 kg/ha (Table: 1); after which no
any popular variety has been released or if is released, most
of us are unaware to that! All varieties are differing in
fruit characters, viz.: taste, flavour, colour, tinges, shape
and size, traits that determine the quality of the fruit and
hence its market value at home and overseas.
Table: Mango varieties, year of release and yield potential
(kg/ha.)*
Name of
variety |
Year of
release |
Yield
potential (kg/ha.) |
Late
season |
Neelum |
1965 |
11070 |
Mid season |
Swarnarika |
1953 |
21000 |
Summer
Behisht Chaunsa |
1959 |
9000 |
Beganpali |
1953 |
20430 |
Saleh Bhai |
1965 |
9450 |
Anwar Ratole |
1967 |
9900 |
Early
season |
Sindhri |
1949 |
21600 |
Zafran |
1958 |
12600 |
Siroli |
1953 |
8000 |
Langra |
1952 |
10000 |
Dusheri |
1951 |
12870 |
Gulab Khasa |
1959 |
9900 |
* Source: Introduction to Agriculture Research in Sindh.
Directorate General, Agriculture Research Sindh, Hyderabad,
June 1990
The mango is known to suffer from a number of diseases caused
by different organisms, which affects different parts of
plants, at all stages of growth and development. Powdery
mildew (Oidium mangiferae), sooty mould (Capnodium romasum or
Tripospermum acorium), fruit rot (Aspergillus niger), leaf
blight (Pestaloptiopsis mangiferae), anthracnose (Glomerella
cingulata-Colletotrichum gloeosporioides), stem blight or die
back (Diplodia spp.), root rot (Rhizoctinia and Fusarium
species) and tip die back (Fusarium equiseta, Alternaria
alternate, Aspergillus niger and Rhizopus nigricans) are
recorded as fungal diseases; bacterial leaf spot (Erwinia
mangifera); and malformation of mango inflorescence (the
actual cause is still not confirmed) are reported from
Pakistan. No information regarding the extent of damage to the
plant is available, but some of these are certainly
responsible for causing considerable damage and become a
limiting factor in many mango-growing areas.
It is also pertinent to mention here that almost all
commercial mango varieties are old, released from 1949 to 1967
and are under cultivation. Therefore, it is a question that
how these varieties, after long period, could be resistant to
the diseases? More or less, all varieties are reported to be
susceptible, to most of the above diseases. Mango growers also
neglect their orchards and show interest only at the time to
decide contract rate and period. Contractors pay their
attention and or interest and try to recover their money spent
on contract and obtain high profit at low cost of production,
but do not think about health and life of mango trees. Even
growers avoid irrigating their orchards at requirement;
interculturing and manure applications are also not carried on
timely. Now it is up to the growers, to whom they may call
responsible for present severe and serious situation of
diseases in mango orchards. What the researchers would like to
do for identification of actual problem. How the existing
disease or complicated disease's case occurred in mango
orchards could be controlled?
However the symptoms of all these possible factor diseases are
summarized hereunder just to guide mango growers and students,
whereas, the researchers are requested to plan their future
strategies against the diseases causing huge loss to tree as
well as fruit, for the benefit of nation and country.
Anthracnose
(Fig 1) is prevalent in almost all parts of the country. The
leaves, petioles, twigs and fruits are attacked. Appearances
of oval and irregular blister like brown spots develop on the
tips, margins and centre of leaves and twigs. Blackening of
petioles, elongated necrotic streaks on young twigs and
branches are observed, and leaves drop down from top to
bottom. Drying and rupturing of affected tissues, drying and
falling of leaves, brightening of blossoms, staining and
rotting of fruits are also main symptoms of anthracnose.
Tip die back disease occurs on the branches/ trunk of infested
trees that start drying slowly at first and suddenly branches
become completely dried / killed resulting gummy substance
oozes out or remains hanging on the tree (Fig 2).
Stem
blight or die back become evident by discoloration and
darkening of the bark as well as exudation of gum from
infected portion (Fig 2). The withering of leaf tips and
shedding of leaves (Fig 3), the twigs dying back from top to
bottom is also one of the major evident of this disease. Brown
streaks are observed on vascular tissues by length wise
splitting of diseased twigs (Fig 3). Almost all mango
varieties are reported as susceptible to this disease.
Root
rot is also prevalent in almost all orchards; manifest itself
as withering and drying of the plant from top to bottom and
whole plant die up (Fig 4). Initially rootlets are affected
and are rotten, later on the smaller, tertiary roots and
ultimately the bigger, secondary and primary- main roots are
infected which result in gradual decline of the plant and the
plant die (Fig 4). The uptake of nutrients and water is
blocked due to the rotting of the roots, which results in
drying of the plants.
Leaf blight; initially appear as minute yellowish spots on the
upper surface of the mature leaves. The spots become more in
number, bigger in size and often coalesce, forming big
irregular patches. The lower size of the spot is brown in
colour, while upper portion becomes white in centre with a
brownish purple margin that separate diseased and healthy
portion. Some of the symptoms are present in infected mango
trees.
Bacterial
leaf spot is noticed on the leaves as angular water soaked
spots or lesions, surrounded by clear holes. These become
necrotic and dark brown and viscous bacterial exudates deposit
on these necrotic portions that become corky and hard after
drying. Sometimes, longitudinal cracks also develop on the
petioles. Some of the similar signs are present in suffering
mango orchards (Fig 5).
Fruit
rot starts usually in the ripe and over ripe fruits as spots
of different colours, which soon increase in number and size.
Affected fruits may become soft, pulpy and unfit for
consumption. The present situation is so much away from this
problem (Fig 6).
Powdery mildew (Fig 7) is one of the worst diseases affecting
almost every variety and is common in all over Pakistan. It
appears from December to March, as superficial whitish or grey
powdery growth on the flowers and flower buds (inflorescence),
tender leaves, thin stem (shoots and trunk) and spreads to
fruits. Infected flowers fail to open and sometimes shed
before being fertilised and results in a substantial reduction
of fruit set. If the fruit is already set, it may drop off
prematurely. The axis may begin to dry, showing characteristic
dieback symptoms, but dying of mango trees is not due to this
disease, but is another unknown havoc disease.
Malformation
(Fig 7) is very common and widely distributed in orchards (to
a lesser or greater extent) in all over country. Compact
leaves formed at the apex of shoot or in the leaf axil, to
form the bunchy top seedlings and are usually shallow with few
tertiary roots. The tap root may be twisted and may show
necrosis. Sometimes, small leaves appear as shootlets, growth
of which is checked and several similar shootlets arise from
the axil of the scaly leaves and form bunches, which are
thicker than the main stem. Floral aggregation (malformation)
may also appear on shortened primary axil of the
inflorescence, which is further branched to secondary and
tertiary branches, on which flowers are borne in clusters and
no fruit or very poor fruit setting is observed. Infected
inflorescence remains green for long time; no malformed heads
dry up in black masses but persist on trees. The symptoms are
persistent in almost all those gardens in which pruning have
not yet been done.
Sooty mould (Fig 8) appears as black velvety growth on the
leaf surface. The entire leaf surface or portion of the leaf
may be covered with fungal growth and in severe cases the
whole plants are affected. The thin layer formed on the leaf
surface can be rubbed off easily. Under the dry conditions
this may be blown off as small fragments by the wind. The
disease causing fungi in true sense are non pathogenic,
however, photosynthetic activity of the plant is impaired due
to covering of the leaves. The symptoms occurring in diseased
orchards are different to that of this disease.
Sudden death of mango trees (Occurrence of new symptoms,
especially in Sindh)
The present situation of mango orchards, with special
reference to the province of Sindh, needs special attention,
where about all mango orchards are suffering due to an unknown
disease problem, causing sudden death of mango trees. At
present mostly 3 to 5 and most likely 60 to 85 percent of
trees are suffering from this type disease, in various mango
orchards of Sindh. There are different opinion of plant
disease specialists, but I think it is complicated case
emerged mostly due to combine attack of anthracnose, stem
blight or die back, root rot, tip die back, leaf blight,
bacterial leaf spot and malformation diseases, which are
responsible for the decline (dying of trees). That may also be
proved through presence of the symptoms of most of these
diseases in a single plant at same time; isolation of near
about all the fungi causing these diseases from diseased
specimens collected from same single diseased plant; as well
as nature and behaviour of these diseases causing organisms.
High temperature, high relative humidity and weak plants are
main contributing factors in the spread of anthracnose and die
back, while root rot and tip die back caused by Fusarium
species develop more on weak plants, in high soil temperature
and drought conditions. It is also true that dying of trees or
decline is generally observed more in the neglected orchards,
which is common factor. The shortage of irrigation water may
also be another main cause, which helps to the disease causing
organisms to grow, develop and spread more.
However, development of small saprophytic white mushrooms on
dried trunk (stem) of diseased trees (Fig 9), rotting of roots
/ trunks having very bad smell and small holes on trunk (Fig
10) due to inset pests (perhaps because of bark beetles) are
the most common but newly occurring symptoms, which are also
present in almost all mango orchards. The growers are going to
cut-off / remove diseased trees from their orchards because
they feel no way except destruction of diseased mango trees
(Fig 11).
Possible control measures
The researchers had conducted various experiments on the
diseases of mango plants and fruits and evaluated various ways
by which the diseases can be controlled. Therefore, it is
suggested that integrated disease management practices must be
applied by using different fungicides in combination with
suitable insecticides; whereas different cultural practices
may also help to check the diseases. It must be kept in mind
that use of fungicides is not alone source. On the other hand,
it is also pertinent to mention here that the fungicides
increase the cost of production. Their use is risky for the
health of worker. The fungicides decrease the fruit quality
because of their toxic substance residues that may remain
present so much time in the fruit. Therefore, following
integrated disease management principles should be applied.
1. Only healthy seeds, seedlings and plants should be used for
planting and budding or grafting.
2. Inter cropping, mix cropping, cover cropping and or
multiple cropping in or in the surrounding of mango orchards
must be avoided so that the similar possible pathogens of the
sown crop and mango (both) may not be multiplied and spread in
orchards.
3. Irrigation must be applied as per requirement, but not
subject to the availability.
4. Avoid high doses of nitrogen fertilisers, but apply proper
and balanced fertilizers, on the basis of soil type, age and
need of the tree.
5. Proper sanitation of orchards and pruning of trees
(eradication of disease causing organisms through removing and
burning of diseased plants or plant parts) helps to reduce the
infection and growth, development and further spread of the
disease causing fungus or so.
6. Easily available broad spectrum fungicides should be used,
in combination with insecticides at proper dose. However,
encouraging results could be obtained with consulting
pathologist and entomologist.
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