Described on disease history, symptoms, etiology and management

1. Stem canker of Cocoa
Stem Canker of Cocoa
Prepared by: Tanmoy Mondal, B.sc (3rd yr),UBKV

2. Introduction
• The disease was first reported from
West Indies in 1897.
• It is widespread in all cocoa growing
countries of the world.
• The disease appeared in India in 1965.
• After introduction to the country and
occurs in the state of Karnataka
‚Kerala‚and Tamilnadu

3. • The disease attack several
parts of plant.
• Most severe damage occur on
the fruit.
• Initial symptoms appear as a
brown discoloration on the
pods.
• The brown discoloration
spread rapidly in all direction.
Symptoms

4. • Under too wet condition
and very low temperature
‚the pathogen cause stem
canker in a 2-16 year old
plant.
• The fungus attack the plant
at or near soil level.
• It cause water soaked
darkening of bark of trunk.
Symptoms

5. • Reddish brown liquid oozes out
from the lesion which later dries upto
form a rusty deposit.
• The infected area enlarged & may encircle
the stem or the branches.
• The leaves and pods wilt and fall off.
• The branch may show dieback symptom .
• Pod yield reduced markly.
Symptoms

6. Symptoms

7. Etiology
• Causal organism: Phytophthora
palmivora
• Mycelium is
hyaline‚branched‚coenocytic‚intercellul
ar‚sends haustoria into the host cells.
• Mycelium is fine‚white‚cottony growth.
• Sporangiophores arise from mycelium.

8. Phytophthora palmivora
Sporangiophores
Sporangia

9. • Sporangiophores
are branched and
sporangia are
formed at tip of the
branch
• Sporangia are inverted
pear shaped‚ hyaline‚
multinucleate‚with an
apical papilla.
Etiology

10. • Soprangia germinate in
water and release large
zoospores through
papilla.
• Zoospores are
biflagellate.
• The fungi produces
oospores in its sexual
phase.
Etiology

11. Zoospore

12. Oospore
• The oospores are
spherical ‚thick
walled.
• The oospores
germinate by
germ tube that
produce
secondary
sporangia or
germinate directly
into mycelium.

13. • The fungus
also produces
thick walled
‚terminal or
intercalary
chlamydospor
es.
Etiology

14. Life Cycle

15. Mode of Survival/Perpetuation
-The fungus perpetuates through
mycelium ‚chlamydospores and
oospores that may remain dormant in
the infected part.
-In the rainy season‚the pathogen
becomes active and produces
sporangia and zoospores on tree top .

16. • Zoospores‚sporangia are spread by
splashing rain ‚wind‚mechanically by
some insects to other trees.
• Toddy tappers and rhinoceros beetles are
other agents responsible for the spread of
the disease.
Spread

17. • Low temperature of 18-20°C
‚continuous monsoon rains and
wet weather (high relative
humidity) favour the occurrence
and spread of the disease.
Epidemiology

18. Management

19. Management
• Chemical control:
• a)Spraying with Bordeaux mixture @1% or
copper oxychloride @2.5 gm/ lit.
• b)Spraying with systemic fungicides‚
such as Metalaxyl @1gm or Ethazol
@1gm/ lit of water has been found to be
very effective.
• c)Dipping the seedling in the above
mentioned fungicides prior to planting.
• d)Drenching the nursery bed with above
mentioned fungicides.

20. TANMOY MONDAL
Email Id:
tanmoymondal10000
@gmail.com