Published Date: 2011-08-19 10:52:57
Subject: PRO/PL> Black root, cocoa - Cameroon: (SW)
Archive Number: 20110819.2517
BLACK ROOT, COCOA - CAMEROON: (SUD-OUEST)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Tue 16 Aug 2011
Source: Daily Times Nigeria [edited]
Weather threatens Cameroon cocoa season
The world's 5th largest cocoa producer experiences a bumpy start to
the year's  growing season. Drought, hail, and downpours in
different parts of Cameroon have soured the start of the cocoa season
driving down quality, volumes, and prices.
Heavy rains were reported in Cameroon's southwest, triggering the
spread of black root disease. "There have been plenty of downpours,
sometimes going on for 2 weeks non-stop," said a farmer in Konye
[Black root rot of cocoa is caused by several species in the genus
_Rosellinia_. The fungi cause a high rate of mortality of trees,
especially in acidic soils with high organic matter, and often
interact with other pathogens. The name 'black root' refers to the
black fungal hyphae that are produced on affected cocoa roots.
Symptoms resemble other root rots and include wilting, dieback, and
sudden tree death.
The fungi are soil borne and can survive in colonised organic debris
for long times. They are spread with soil, contaminated plant and
other materials, and by mechanical means (including human activities).
They have wide host ranges resulting in many possible pathogen
reservoirs. Disease management is difficult due to the inaccessibility
of underground plant parts to fungicides. It usually requires an
integrated approach and may include exclusion, phytosanitation,
cultural practices, as well as soil treatments with fungicide
drenches, fumigants, or solarisation. Biological control measures are
being investigated. No cocoa varieties resistant or tolerant to black
root have been identified so far.
_Rosellinia_ species affect many important tropical crops, such as
banana, coffee, tea, citrus, rubber, avocado, and timber species.
An undiagnosed disease of cocoa has been reported from SW Cameroon
(ProMED-mail posts 20110309.0762 and 20101003.3584), but it is not
clear whether this may be the black root outbreak reported above.
Cameroon and neighbours:
_Rosellinia_ black root symptoms on clove:
Information on cocoa diseases, including black root, via:
_Rosellinia_ diseases and pathogen information, including cocoa black
Research on biocontrol of _Rosellinia_:
_Rosellinia_ taxonomy and species list via:
Review of cocoa production in Cameroon:
Cocoa pests and diseases -- references and resources: