2. SYSTEMATIC POSITION OF PATHOGEN
• Domain : Eukarya
• Kingdom : Fungi
• Phylum : Ascomycota
• Sub phylum : Pezizomycotina
• Class : Dothideomycetes
• Sub class : Dothideomycetidae
• Order : Capnodiales
• Family : Mycosphaerellaceae
• Genus : Mycosphaerella (Cercospora)
3. • EARLY LEAF SPOT: Mycosphaerella arachidis
(Cercospora arachidicola) anamorph
Mycelium : intercellular becoming
intracellular, lack in haustoria, dark brown in colour
Conidiophores : 5 to many, yellowish brown,dark
at base, unbranched,continuous or with 1 or 2 septa
Conidia : subhyaline,pale yellow, often
curved, 1 to 12 septate, round at base and subacute at
tip.
4. • LATE LEAF SPOT: Mycosphaerella berkeleyii
(Cercospora personata) anamorph
Mycelium : septate, intercellular, branched haustoria, stroma
dense and pseudoparanchymatous.
Conidiophores: pale to olivaceous brown in colour, one to 3
geniculated or not, septate or continuous, simple or rarely
branched emerging through ruptured epidermis in dense
fascicle.
Conidia: cylindrical, olivaceous, straight or slightly curved,
mostly 3-4septate, rounded at apex, base shortly tapered.
6. EPIDEMIOLOGY
• Prolonged high relative humidity (more than 85%)
• continuous for 3days
• Low temperature(20˚C)
• Dew on leaf surface
7. PRIMARY INOCULUM & RESISTANCE OF PLANT
• Ascospores may not be the source of primary inoculum.
• Conidia present in crop residue –most important primary inoculum.
• Secondary spread of the spore through wind and water splash.
• High level of ascorbic acid in plant –more susceptible.
• high level of riboflavin in plants – provide resistance.
11. Lifecycle Conidiophore on
lower leaf surface
Spores disseminated by
wind, splashing water, and insects
Infection on host tissue
Pseudothecium
Ascospore
Overwintering
stages on
crop residue
Intercellular mycelium
with haustoria
Late leaf spot
Lower leaf surface
12. Symptoms
• The symptoms of two pathogens may occur
simultaneously on the same leaf.
• Lesions first appear as a chloratic lesions about 10 days
after spore deposion.
• Mature sporulating lesions are visible about 15 days
after spore deposition.
• Beginning- on leaf only
• Later-on stem also
13. Symptoms of early leaf spot
• Sub circular to irregular shape.
(tend to coalesce later)
• Reddish brown to black on upper leaf
surface(surrounded by a yellow chloratic halo).
• Light brown on lower leaf surface.
• Absent or indistinct on lower leaf .
• Sporulation mainly occurs on upper leaf surface and
turn to reddish brown colour.
• Occurs 3-4 weeks after sowing.
14.
15. Symptoms of late leaf spot
• Smaller spots and more nearly circular than
early leaf sot lesion (1 to 6 mm in dia).
• dark grey or black on lower leaf surface.
• No yellow halo around them.
• Concentric rings of conidia macroscopically
visible on the lower surface.
• Symptoms also develop on petioles, stipules,
stems and pegs.
• Occurs 5-7 weeks after sowing.
16. EARLY LEAF SPOT LATE LEAF SPOT
Cercospora arachidicola
LARGER SPOTS
NOT PERFECTLY CIRCULAR
YELLOW HALO IS SURROUND THE SPOT
LOWER SURFACE LIGHT BROWN IN COLOUR
RAPID DEVELOPMENT
CONIDIA MOSTELY CONFINED TO UPPER SURACE
CONCENTRIC RING NOT PRODUCED
Cercospora personata
SMALLER SPOTS
MOST NEARLY CIRCULAR
NOT YELLOW HALO OCCURS, MAY OCCUR IN LATER STAGE
LOWER SURACE DEEP BLACK IN COLOUR
SLOW DEVELOPMENT
CONIDIAL PRODUCTION RESTRICTED TO LOWER SURFACE
CONCENTRIC RING PRODUCED BY CONIDIOPHORES
17. MANAGEMENT
Cultural method:
• summer deep ploughing
• weed management, crop rotation
• eradication of volunteer groundnut plants
• field sanitation, soil solarisation
• use of disease free seed material
• row planting with intercrop of sorghum or cumbu @ 3:1 ratio
• apply optimum dose of N, P fertilizers
• use of resistant varieties (ALR 1 –moderately resistant)
18. • Chemical method:
• seed treatment with 2g carbendazim or thiram /kg of
seed.
• soaking of seeds in 0.5% CuSO4 –half an hour
• spraying of carbendazim 0.1% or mancozeb 0.2% or
chlorothalanil 0.2% or Dithane Z – 78 , Dithane M-45 –
0.2%
(repeat 15 days after 1st spray)
19. •Biological method
• Soil application of 2 kg/ha Trichoderma viride mixed
with 25 kg FYM.
• Seed treatment with Pseudomonas fluorescence @10
g/kg of seed.
• Foliar spray of 2 % Trichoderma viride or
Pseudomonas fluorescence
20. Reference :
• PD Sharma, 2006, Plant Pathology, Narosa publishing house, New
Delhi.
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