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TIKKA DISEASE OR LEAF SPOT
Tikka disease is reported from all groundnut growing countries of the world such as
Africa, Australia, China, India, Indonesia,Malaysia, Philippines, Sri Lanka and USA. The disease is caused
by two fungal plant pathogens i.e. Cercospora arachidicola and Cercosporidium personatum.
The perfect stages of both these fungal pathogens (Mycosphaerella arachidicola and M. berkeleyii) play
important role in primary infection and pathogen survival. The yield loss from tikka disease has been
reported from 20-50 per cent but may be increased with association other diseases. The all groundnut
varieties grown in India are susceptible to tikka disease.
Symptoms: The primary symptoms of the disease are appearing in 35 to 60 days old plants. The tikka
disease occurs as two distinct types of lea spots caused by two species of Cercospora. C. personatumcauses
small (1-6 mm), almost circular and dark coloured spots on the leaves, stipules, petioles and stem which may
coalesce to form a large dark brown to black irregular patch. There may be few to many spots on each leaf.
The severe infection or spotting on the leaves causes premature dropping. The disease is more severe at the
time between flowering and harvesting, when the climatic conditions are favourable. The leaf spots caused
by Cercospora arachidicola are almost circular to irregular, large (1-10 mm), surrounded by bright yellow
haloes and dark brown centre. The conidia are formed on upper surface of leaf
while C. personatum produced conidia on lower surface of leaves with concentric rings.
Causal Organism: The causal organism of tikka disease
are Cercospora
arachidicola Hori
(perfect
stage
of
the
pathogen:Mycosphaerella
arachidicola )
and Cercosporidium
personatum (perfect stage of the pathogen: Mycosphaerella
berkeleyii ). The mycelium of C. personatum is intercellular, brown,
septate, branched and slender with haustoria. The conidia are hyaline,
18-60 x 6-11 µm, 2-7 septate and borne singly on short, 26-54 x 5-8 µm
conidiophores. The conidiophores are produced in bunches from the
hymenial layer of sub-epidermal region. The mycelium
of C. arachidicola is inter and intracellular, brown, septate, branched
and without haustoria. The conidiophores are 22-45 x 3-5 µm,
yellowish brown, septate and conidia are hyaline or pale yellow,
obclavate, 4-12 septate measuring 38-108 x 3-6 µm.
Disease Cycle: The tikka disease of groundnut is soil borne. The
pathogen C. arachidicola and C. personatumdisseminated by wind which is blown from leaf to leaf. The
primary infection of disease is caused by conidia found on the plant debris in the soil. The spores remain
viable in the soil for a long time and infect the succeeding crop under favourable environmental conditions.
High humidity and relatively low temperature is essential for initiating the fungal infection. It is observed
that the high nitrogen fertilizer increases disease intensity.
Epidemiology:Warm and moist weather conditions encourage development of epidemics. Optimum
temperature is 24-28ºC with a period of 3 days of high humidity. The incubation period is 8-15 days.
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Control:
1. Plant disease debris should be burnt.
2. Seed dressing with a suitable fungicide like Benlate and Vitavax (2 gms/kg of seed).
3. Foliage spray with Bordeaux Mixture (4:4:50), Dithane M-45 (0.2%), Benlate and Bavistin (0.1%)
gives good results.
4. Early maturing and spreading type varieties are less liable to attack of the disease.
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Mahali/Fruit Rot/Koleroga
Phytophthora palmivora causes bud-rot of palms, fruit-rot or kole-roga of coconut and arecanut. These are
among the most serious diseases caused by fungi and moulds in South India. It occurs almost every year
in Malnad, Mysore, North & South Kanara, Malabar and other areas. Similar diseases of palms are also
known to occur in Sri Lanka, Mauritius and Sumatra. The causative organism was first identified
as Phytophthora palmivora by Butler in 1917.
Causal Organism
Phytophthora meadii (major species), P. arecae, P.heveae
Symptoms
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This dreaded disease occurs in all the arecanut growing regions receiving
heavy rainfall
The crop loss varies from 10-90%
Mahali is weather dependent and seen during monsoon season from JuneOctober
Characteristic symptom is rotting and extensive shedding of the immature
nuts during south west monsoon
The first symptom appears as dark green/yellowish water soaked lesions on
the nut surface usually near the soft inner perianth region and infected nuts
lose its natural green luster
The lesions gradually spread covering the entire nuts (before or after
shedding) which consequently rot and shed
A felt off white mycelial mass envelopes on entire surface of the fallen nuts
As the disease advances the fruit stalks and the axis of the inflorescence rot and dry, sometimes being
covered with white mycelial mats
Infected nuts are lighter in weight and possess large vacuoles
Dark brown radial strands on kernel make them unfit for chewing
Infection occurring later in the season results in rotting and drying up of nuts without shedding called
‘Dry Mahali’
Spread of Disease
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The fungus survives as oospores, chlamydospores and mycelium in soil, on fallen nuts, on dried nuts
and inflorescence remaining in the crown. The spread of the disease is by wind and wind blown rain
Continuous heavy rainfall with intermittent bright sunshine hours, low temperature of 20-230 C,
constant high relative humidity of more than 90%, wind, cloudy weather, plantations situated in
valley surrounded by rubber plantations etc. favours the outbreak of the disease
Control
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Prophylactic spray of 1% Bordeaux mixture with stickers once before the onset of south west
monsoon followed by second and third applications at 40-45 days interval
Cover bunches with polythene sheets before monsoon rains
Collect and destroy all fallen and infected nuts
 Remove and destroy all completely affected inflorescence and immature bunches
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