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Friday, January 11, 2013
Mango Diseases and Management
Mango
Diseases
Powdery
Mildew
(Oidium mangiferae)
Powdery mildew is one
of the most serious diseases of mango affecting almost all the varieties.
The characteristic symptom of the
disease is the white superficial powdery fungal growth on leaves, stalk of panicles, flowers and young fruits. The
affected flowers and fruits drop pre-maturely reducing the crop load
considerably or might even prevent the fruit set. Rains or mists accompanied by
cooler nights during flowering are congenial for the disease spread.
Control
: Alternate spraying of Wettable sulphur 0.2 per cent (2 g Sulfex/litre),
Tridemorph O.1 per cent (1 ml
Calixin/litre) and Bavistin @ 0.1 % at 15 days interval are recommended for
effective control of the disease. The
first spray is to be given at panicle emergence stage.
Anthracnose
(Colletotrichum gloeosporioides) :
It is of widespread
occurrence in the field and in storage. The disease causes serious losses to young shoots, flowers and
fruits under favorable climatic
conditions (high humidity, frequent rains and the temperature range of
24-32°C). The disease produces leaf spot, blossom blight, withered tip, twig
blight and fruit rot symptoms. Tender shoots and foliage are easily affected
which ultimately cause die back of young branches. Older twigs may also be
infected through wounds, which in severe cases may be fatal. Black spots
develop on panicles. Severe infection destroys the entire inflorescence
resulting in failure of fruit setting.
Young infected fruits develop black spots, shrivel and drop off. Fruits infected at mature stage carry the
fungus into storage and cause considerable loss during storage, transit and
marketing.
Control
: The diseased twigs should be pruned and burnt along with fallen leaves.
Spraying twice with Carbendazirn
(Bavistin 0.1%) at 15 days interval during flowering controls blossom
infection. Spraying of copper fungicides
(0.3%) is recommended for the control of foliar infection. Postharvest disease
of mango caused by anthracnose could be controlled by dip treatment of fruits
in Carbendazim (0.1%) in hot water at 52 C for 15 minutes.
Die
Back
(Botryodiplodia (Lasiodiplodia) theobromae) :
Die back is one of the
serious diseases of mango. The disease on the tree may be noticed at any time
of the year but it is most conspicuous during October-November. The disease is
characterized by drying of twigs and
branches followed by complete defoliation, which gives the tree an appearance
of scorching by fire. Initially it is
evident by discoloration and darkening of the bark. The dark area advances and extends outward along the veins
of leaves. The affected leaf turns brown and its margins roll upwards. At this stage, the twig
or branch dies, shrivels and leaf falls. This may be accompanied by exudation of yellowish brown
gum.
Control
: Pruning of the diseased twigs 2-3 inches below the affected portion and
spraying Copper Oxychloride (0.3%) on
infected trees controls the disease. The cut ends of the pruned twigs are
pasted with Copper Oxychloride (0.3%).
Phoma
Blight
(Phoma glomerata) :
The symptoms of the
disease are observed only on old leaves. Initially, the lesions are angular,
minute, irregular, yellow to light
brown, scattered over leaf lamina. As the lesions enlarge, their colour
changes from brown to cinnamon and they
become almost irregular. In case of severe infection such spots coalesce forming patches resulting in
complete withering and defoliation of infected leaves.
Control
: The disease is controlled by spraying Benomyl (0.2%) just after the
appearance of the disease followed by
0.3% Miltox (Copper Oxychloride + Zineb) at 20 day interval.
Bacterial
Canker
(Xanthomonas campestrispv. mangiferaeindicae) :
Canker is a serious
disease in India. The disease causes fruit drop (10-70%), yield loss (10-85%)
and storage rot (5-100%). Many
commercial cultivars of mango including Langra, Dashehari, Arnrapali, Mallika and Totapuri are susceptible to this
disease. The disease is found on leaves, petioles, twigs, branches and fruits. The disease first
appears as minute water soaked irregular lesions on any part of leaf or leaf lamina. Several lesions coalesce
to form irregular necrotic cankerous patches. In severe infections the leaves turn yellow and drop
off. Cankerous lesions also appear on petioles, twigs and young fruits. The water soaked lesions also
develop on fruits which later turn dark brown to black. They often burst open, releasing highly contagious
gummy ooze containing bacterial cells.
Control
:Three sprays of Streptocycline (0.01%) or Agrimycin-100 (0.01%) after first
visual symptom at 10 day intervals and
monthly sprays of Carbendazim (Bavistin 0.1%) or Copper Oxychloride (0.3%) are effective in controlling the disease.
Red
Rust
(Cepbaleuros virescens) :
The disease attack
causes reduction in photosynthetic activity and defoliation of leaves
thereby reducing the vitality of the
host plant. The disease is evident by the rusty red spots mainly on leaves
and sometimes on petioles and bark of
young twigs. . The spots are greenish grey in colour and velvety in texture. Later, they turn reddish brown. The
circular and slightly elevated spots sometimes coalesce to form larger and irregular spots. The affected
portion of stem cracks. In case of severe infection, the bark becomes thick, twigs get enlarged but
remain stunted and the foliage finally dries up.
Control
: Two to three sprays of Copper Oxychloride (0.3%) is effective in controlling
the disease.
Sooty
Mould
(Meliola mangiferae) :
The disease is common
in the orchards where mealy bug, scale insects and hoppers are not
controlled efficiently. The disease in
the field is recognized by the presence of a black sooty mould on the leaf surface. In severe cases, the trees turn
completely black due to the presence of mould over the entire surface of twigs and leaves. The severity of
infection depends on the honey dew secretion of the above insects. Honey dews secretions from insects
stick to the leaf surface and provide necessary medium for fungal growth. Although the fungus causes
no direct damage, the photosynthetic activity of the leaf is adversely affected.
Control
:Pruning of affected branches and their prompt destruction followed by spraying
of Wettasulf (0.2% )+ Metacid (0.1 %)+
gum acacia (0.3%) helps to control the disease.
Diplodia
Stem-end Rot(Lasiodiplodia
theobromae) :
The fungus enters
through mechanically injured areas on the stem or skin. The fungus grows from the pedicel into
a circular black lesion around the
pedicel.
Control
: Careful handling to minimize mechanical injuries. Postharvest dip of fruits
in Carbendazirn (0.1%) in hot water at 52 ± 1°C for 15 minutes controls the
disease in storage and transit.
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