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Stem diseases
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INTRODUCTION:
 Stem diseases are the diseases that infect the stem portion.
 E.g. dieback, pink disease and stem canker etc., since the
diseases infect the stem portion it affects the movement of water/
nutrient food materials from root to leaves vice versa.
 The stem diseases may infect the outer tissues (e.g. stem
canker) or it may intrude inside to stem portion (e.g. heart rot ).
 If the infection is external it would not reduce the yield much.
 If it is severe it kill the entire plant.
 Some time the stem disease visible externally as bleeding (stem
bleeding) fruiting bodies (e.g heart rot) or drying from tip
backwards (dieback)
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Stem canker:
The fungus attacks the branches,
forming cracks and lesions along the
stem.
The affected branch wilts as the stem
tissues
are
killed,
arresting
translocation of nutrients.
The disease spreads from one plant to
another by air borne infections.
The perithecia are formed on the
infected tissues.
The fungus remains inside the infected
tissues beneath the bark and becomes
active whenever climatic conditions are
favorable.
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Control:
The infected should be cut and destroyed
and Athe cut end painted with Bordeaux
paste.
Other sanitary measures such as
spraying after pruning, protecting the
wounds with Bordeaux paste and
preventive sprays against insect attack
may prevent the onset of the disease.
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Verticilium wilts:
Symptoms:
The infected ones show dwarfing and
stunting due to the shortening of the
internodes and generally do not flower
and fruit.
In the infection takes place after the
plan has flowered or fruited, the floral
buds and the fruits become distorted,
flaccid and finally drop off.
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Casual organism:
Verticillium dahlia
Mode of spread:
The pathogen is soil – borne and the primary inoculums
usually consists of the organism in the soil.
Control:
Benlate 0.1 per cent applied as foliar spray as well as soil
application is effective in reducing the wilt incidence.
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Gummosis:
 This is one of the severe diseases of
citrus in almost every country where
these trees are grown extensively.
 It is found in all parts of India,
affecting almost every variety.
 There are at least six species of
Phytophthora
known
to
be
associated with the disease.
 They are:
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Symptoms:
The disease manifests itself in the form of water
soaked large patches on the basal portions of the
stem, near the ground level.
Soon these patches turn brown and
the bark may split, through which a
gum like ooze exudes.
The disease spreads in both directions in
the stem, reaches the main branches and
the roots.
The external symptom as are restricted to the
basal stem, whereas the infection spreads
further.
The external symptom as are restricted to the basal
stem, whereas the infection spreads further.
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Stem gall:
Symptoms:
It appears in the form of tumor like
swellings on the veins, leaf stalks,
peduncles and other above
ground plant parts.
The swelling gradually enlarge
and reach the size of about 2 cm
long and 0.5 to 1 cm broad.
The infected plants are stunted,
and when the inflorescence is
attacked seed production is
reduced considerably.
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Casual organism: Protomyces macrospores
Control:
There is no effective method of controlling
this disease, except to adopt field
sanitation practices and destroy the
diseased plants.
Infested seeds having galls should not
be used for sowing.
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Symptoms:
Stem bleeding:
This is a common disease of
coconut and areca nut in many
parts of South India.
It is characterized by reddish
brown ooze, from the stem
cracks, which dries up to form a
black crust.
When
diseased
trees
are
examined by scooping the
infected tissues, the infected
portion
is
seen
discolored
yellowish brown.
Except the vascular bundles the
other tissues are disintegrated
and often large cavities are
formed in the diseased stem.
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Control:
In the case of new infections, the
disease is controlled by scooping out
the diseased tissues and sterilizing the
open wound with the heat of a burning
torch of coconut leaves, followed by the
application of hot tar to the surface, after
which the cavity is filled with saw dust
and tar.
Bordeaux paste or mercurial
fungicide is also applied.
The same treatment may be applied
to areca palms affected by the same
fungus.
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Die back:
Symptoms:
The symptoms begin with die back
of small branches and twigs,
yellowing of leaves and heavy
bearing of small fruits.
As the disease progresses the
symptoms intensify, resulting in
severe chlorosis and mottling,
reduction in leaf size and number,
and wilting.
After 7-8 years the plant may die, by which time there may
be no leaf formation, the branches get dried up and the
plant appears wilted almost completely.
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Control:
Good cultural practices, improvements in the
fertility level of soil and good drainage benefit
in reducing decline.
Periodical spraying against possible insect
vectors. i.e. aphids, should be done.
Involvement of Phytophthora spp.and Oidium should
be avoided by regular phytolactic measures.
Proper rootstock – scion combination
should be used.
The intensity of the disease is substantially
reduced by cross protection with milder strains
of the virus.
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Stem canker:
Clavibacter michiganese
Symptoms:
The bacterium affects the various
above ground plant parts, including
the stem, causing canker- like
infections.
Firstly, light brown streaks appear
on the stem and leaf petioles, which
turn black and cankerous.
When the affected stem or petiole is
cut, creamy yellow bacterial ooze is
seen.
On the stem infection starts as
water soaked lesions, with a
white halo, later turning dark
brown, corky and cankerous.
At times these cankers may deep
seated and cover a large portion of
the fruit.
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Control:
The seed borne infection can be
eradicated by hot water treatment
or by treating the seeds in organo
mercurial slurry or 500 ppm of
streptomycin solution.
Spraying the plants with 500 ppm of
streptomycin, two or three times at the
fruiting stage, would also help to
reduce the intensity of the disease.
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Mode of spread:
The
disease
spread
agricultural implements,
cutting knife.
through
including
In the field the infection spreads by
wind and water.
Control:
Gummosis disease can be controlled by selecting
disease free plants, and adopting strict field sanitation
practices.
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To sum up
• Stem diseases are the diseases that occur in the stem portion. eg.
dieback, pink disease and stem canker etc., Since the pathogens
infect the stem portion it affects the movement of water/ nutrient food
materials from root to leaves vice versa.
• The pathogen may infect the outer tissues (e.g. stem canker) or it
may intrude inside to stem portion (e.g. heart rot. Some times the
stem diseases becomes visible externally as bleeding (stem
bleeding) fruiting bodies (e.g heart rot) or drying from tip backwards
(dieback)
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