Concern for chocolate manufacturers
fall dramatically if diseases, which have devastated South American
cultivation of cacao (the raw material used for producing
chocolate) over the past 15 years, were to spread to some of the
world's other cacao producing regions.
Writing in the Summer 2004 edition of Biologist, Dr Gareth Griffith of the University of Wales, Aberystwyth, warns that increased trade and improved transport links between South America and other cacao growing countries could allow fungal infections such as Witches' Broom Disease and Frosty Pod Disease to spread to these hitherto uninfected areas. Alone and in combination these diseases can cause near total crop failure.
The recent spread of other fungal pathogens such as sudden oak death (caused by Phytophthora ramorum) highlights the fact that global trade is not risk-free. Formal risk assessments need to be conducted to minimise the spread of plant pathogens.
Whilst chocolate lovers around the world may despair at the prospect, the effect of the diseases on the cacao growing communities themselves has been devastating. According to Dr Griffith, accidental assistance from humans has been instrumental in the spread of the disease around South America. The rapid spread of the disease from Surinam to Ecuador and Trinidad in the early 20th century was probably due to transport of superficially healthy but infected cacao pods. In each of these countries arrival of the disease led to a halving of cocoa production within a decade.
"In the 1970s, extensive deforestation and oil exploration in Amazonian Ecuador, encouraged farmers to migrate across the Andes, bringing the disease with them. Similar developments in Brazil led to the establishment of cacao plantations in Amazonia and the inevitable occurrence of the disease.
"Disastrously, expertise in cacao cultivation for these new plantations was imported from the main Brazilian cocoa area in Bahia on the Atlantic coast and, ultimately the disease spread to Bahia by these migrating workers," said Dr Griffith.
In Bahia, where the first incidence of the disease was observed in 1989, the ravages of WBD have been worse than in any of the other infected regions. A large area centred upon the town of Ilheus, which was built on the wealth of cacao plantations, has suffered economic devastation.
It is estimated that 200,000 people were put out of work, with a further two million people being indirectly affected. Knock on effects have included a soaring crime rate and extensive rural depopulation, though in recent years there are some signs of recovery due to the planting of more tolerant cacao varieties.
"The great fear is that improved travel links, especially direct air and sea travel between tropical countries by both people and cargo, could lead to the spread of Witches Broom Disease to countries such as the Ghana where cacao generates a large proportion of national GDP," said Dr Griffith. "We need to learn from past mistakes."
Witches' Brooms Disease is so named because the growing parts of the cacao tree become swollen and branched, giving the appearance of a witches broom. It is caused by the pathogen Crinipellis perniciosa, and despite a century of research, no truly effective control strategy has been devised.
