This document discusses castor seedling blight caused by the oomycete Phytophthora nicotianae. It causes seedling mortality as high as 30-40% under conditions of prolonged rainy seasons. Symptoms include circular leaf spots and stem lesions that cause seedling death. The pathogen produces non-septate mycelium and sporangia. Management involves avoiding low-lying areas for sowing, seed treatment with Trichoderma and metalaxyl, and soil drenching with copper oxychloride or metalaxyl. The document also briefly discusses castor rust caused by Melompsora ricini, which produces yellow pustules on leaves causing premature defoliation.

1. SUBMITTED BY COURSE TEACHER
ROSHAN SARMILA. A Dr. S. PARTHASARATHY
ID. No. 2016021038 Asst. Prof., (Plant Pathology)
COLLEGE OF AGRICULTURAL TECHNOLOGY
Affiliated to Tamil Nadu Agricultural University, Coimbatore
Kullapuram, Via Vaigai dam, Theni-625 562
CASTOR SEEDLING BLIGHT

2. SIGNIFICANCE
• Castor oil plant (Ricinus communis L.,
Euphorbiaceae) - Nonedible oilseed crop of arid
and semi arid regions of India.
• Originates from tropical Africa.
• Seeds contain Ricin – extremely toxic protein.
• Oil has industrial and medicinal uses such as
nylon, fibre, jet engine lubricants, dyes, soaps,
oinments, paints, varnishes.

3. In world,
India is largest producer – 55-60 % TGP
Area - 12.33 lakh ha
Production - 19.64 lakh t
Productivity - 1592 kg / ha
In India,
Gujarat is largest producer – 14.93 lakh t

4. DISEASE
• Seedling blight – Phytophthora nicotianae (=P.
parasitica) (Dastur) water house.
• Common disease in India.
• First reported from Pusa, Bihar ( 1909) in
moderate to severe form.
• Seedling mortality – 30- 40%
• Favoured by ill drained and prolonged rainy
season( end of june to september).

5. Also reported in UP in 1948 and Hydrebad in
1947.
DISTRIBUTION:
UP, AP, Telangana, Karnataka, Bihar, Gujarat.

6. Spot on older leaves Leaf blighting
Dead seedling
© Vikaspedia.in

7. SYMPTOMS:
 Leaves -Circular, dull green patch on both
surface.
 Spreads and leaf to rot and hanging down.
 Stem - Cause withering and death of seedling due
to destruction of growing point or by the collapse
of stem.
 Initailly on young leaves and spread petiole, stem
causing black discolouration and severe
defoliation.

8. Spot on older leaf:
 Leaf spots turn yellow and then brown concentric
zones of lighter and darker colour formed.
 Affected leaves shed prematurely.
 Moist – very fine whitish haze is found on under
surface of the leaf spot.
 Direct attack of stem is not very common if it
means damage is less due to the presence of
cuticularised epidermis in older leaves resist
penetration.

9. PATHOGEN:
 Non septate, inter and intra cellular hyalin
mycelium.
 Sporogiophores emerge through the stomata on
the lower surface singly or in groups.
 A single colourless ovoid or roundish
sporangium is borne at the tip of sporongiophores.

10.  A ripe sporangium liberates zoospores when put
in water. Which varies from 5 to 45 in each
sporangium.
 Fungus also produces oospore and
chlamydospores.
 It also produces infection on the leaf of sesamum,
this might serve as a collatral or alternative host of
the fungus.
 Aesexual spore: Zoospore.
 Sexual spore: Oospore.

11. Zoospore
©Forestryimages.org

12. LIFECYCLE
© researchgate.net

13. SYSTEMATIC POSITION
Kingdom: Chromista
Phylum: Oomycota
Class: Peronosporea
Order: Peronosporales
Family: Peronosporaceae
Genus: Phytophthora
Species: parasitica

14. FAVOURABLE CONDITION:
• Continuous rainy weather.
• Low temperature (20-25◦C).
• Low lying and ill drained soils.
MODE OF SPREAD:
Primary source :
Pathogen remains in soil as chlamydospores and
oospores.
Fungus also survive on host like potato, tomato,
brinjal, sesamum.
Secondary source:
Wind borne sporangia.

15. MANAGEMENT:
 Ill drained, damp, low lying localities should be
avoided for sowing castor.
 Seed dressing with 4g Trichoderma viride
formulation and 3g Metalaxyl (Phenyl amide
compound) per kg of seed.
 Soil drenching with Copper oxychloride (Blue
copper) @ 3g/lit or Metalaxyl 2g/lit.

16. SUBMITTED BY COURSE TEACHER
ROSHAN SARMILA. A Dr. S. PARTHASARATHY
ID. No. 2016021038 Asst. Prof., (Plant Pathology)
COLLEGE OF AGRICULTURAL TECHNOLOGY
Affiliated to Tamil Nadu Agricultural University, Coimbatore
Kullapuram, Via Vaigai dam, Theni-625 562
CASTOR RUST

17. CASTOR RUST
© bowerbird.org.au

18. CASTOR RUST
Melompsora ricini
 It has been recorded on castor oil plant, in Africa,
Asia and southern Europe.
 M. ricini known only on its uredinial and telial
states.
 In Australia, M. ricini was first collected (BRIP
25782) in Brisbane in Auguest, 1999.
 Within weeks the rust was found in perth.
 Yield loss 89.9%, affects rearing of eri silkworm.

19. SIGNIFICANCE
 Controlling the rust with hyperparasites has been
attempted but not found to be economic
importance.
 It is suggested that at the first sign of infection,
diseased leaves should be destroyed.

20. SYMPTOMS
 Minute, orange-yellow coloured, raised pustules
appear with powdery masses on the lower surface
of the leaves and the corresponding upper surface
of the leaves are yellow.
 Often the pustules are grouped in concentric rings
and coalesce together to for drying of leaves.
 Pale leaf spots eventually develop into spore
producing structures called pustules.

21.  Some cases there may be dozen of pustules on a
single leaf.
 Severely affected often turn yellow and fall
prematurely.
 Heavy infection often reduces the vigour of the
plant. In extreme cases (e.g. with antirrhinum rust)
the plant can be killed.

22. PATHOGEN
 The hyphae collect beneath the epidermis of the
leaf and form a minute cushion.
 The urdeospores arise beneath the epidermis on
the tips of branched hyphae.
 Stout club-shaped paraphyses are also formed in
the sorus.

23.  At maturity the epidermis ruptures releasing
clouds of spores.
 The uredospores are round or eliptic, warty and
orange in colour and measure 25-29 × 19-25µ.
 They germinates by germ tube which comes out
from the pores and infects fresh leaves of castor.
 Melompsora ricini is pathogenic to Euphorbia
obtusifolia, E.ipecacuanha, E.geniculata and
E.marginata besides 24 strains and varieties of
R.communis.

24. ©Collections.daff.qld.gov.au

25. SYSTEMIC POSITION
Kingtom: Fungi
Phylum: Basidiomycota
Class: Urediniomycetes
Order: Uredinales
Family: Melampsoraceae
Genus: Melampsora
Species: ricini

26. Spreads:
1. Chiefly by urediospores, and sometimes by wind.
Distribution:
1. The disease occurs in Bombay, Deccan districts,
Coimbatore and Nagpur.
2. It usually appears in Bombay between November
and February on castor sown in June.

27. Favourable condition
Common in India – Nov-Feb-Annual crops.
Geographical distribution:
Africa (Algeria, Congo, Egypt, Ethiopia, Kenya,
Libya, Malawi, Morocco, Mozambique, Rhodesia,
Sudan, Tanzania, Uganda); Asia (Ceylon, Cyprus,
India); Europe (Italy, Lusitania, Portugal).
(From the literature and Herb. IMI)

28. HOSTS
On Ricinus communis; also by inoculation on
1. Euphorphia geniculata,
2. E. ipecacuanha,
3. E. marginata,
4. E. obtusifolia.

29. MANAGEMENT
• Rogue out the self sown castor crops and other
weed hosts.
• Spraying the crop with fine sulphur powder @20-
30 kg /ha.
• Spray Mancozeb (Indofil M-45) at 2kg/ha or
Propioconazole (Tilt) 1 lit/ ha.

30. REFERENCE
• Das.P.C., 2018. Plant Disease. Kalyani Publishers,
Ludhiana.
• Rangaswami.G., Mahadevan.A., 2016. Disease of
Crop Plants in India. (Fourth edition). PHI
learning private limited Delhi.
• Agritech.tnau.ac.in/crop-protection/crop-prot-
crop%20disease-oilseeds-castor.html