A fifth of the cacao beans used to make chocolate are lost to plant diseases every year - and things could get worse, according to scientists.
Randy Ploetz, plant pathology professor at the University of Florida, says that losses would be even greater if some of the diseases were spread.
"Plant diseases are the most important constraints to cacao production and the continued viability of the world's confectionery trades," he said.
Currently, 4 million metric tons of beans worth more than $4 billion are produced each year. The global chocolate market is worth $75 billion annually.
According to Ploetz, the three most important and damaging cacao diseases are black pod, frosty pod, and witches' broom. Black pod occurs worldwide and has the largest impact, while frosty pod and witches' broom are restricted to tropical America.
"Frosty pod and witches' broom would devastate cacao production in West Africa, where almost 70 per cent of all production occurs," said Ploetz. "In this region, either disease could reduce yields by an additional one million more metric tons per year."
Advances have been made in protecting the cacao crop against disease. Scientists from the Agricultural Research Service (ARS) for example recently claimed to have located the genetic markers that help cocoa resist disease.
The scientists found the markers for resistance to witches' broom, a disease caused by the fungus Moniliophthora perniciosa, the main killer of Theobroma cacao trees. The findings, which were presented earlier this year at the biennial symposium on cocoa, could help cocoa farmers tackle the list of diseases that endanger supplies.
This development follows news in the later half of 2005 that the fungal pathogens causing witches' broom and frosty pod may be linked. The discovery was made by molecular biologist Cathie Aime who analysed the plant's DNA.
New insights and current research on cacao diseases, as well as resistance to and management of the diseases, will be addressed during the Cacao Diseases: Important Threats to Chocolate Production Worldwide symposium held 30 July, during the joint annual meeting of The American Phytopathological Society, Canadian Phytopathological Society, and the Mycological Society of America.
The joint meeting will be held 29 July to 2 August 2006, at the Centre des Congres de Quebec, Canada.