Ghana and Ivory Coast are struggling to contain the spread of a disease hitting their cocoa crops, experts have warned.
Cocoa is key to the Ghanian and Ivory Coast economies
Efforts to tackle swollen shoot virus are having little effect, Ghanaian researcher H Dzahini-Obiatey told a gathering of experts in Costa Rica.
The virus, which defoliates and can eventually kill cocoa trees, has been damaging yields in West Africa.
Cocoa, which is the key ingredient in chocolate, plays a major part in the economies of Ghana and Ivory Coast.
The struggle against swollen shoot virus is "not yet lost, but it is far from won," Mr Dzahini-Obiatey told an international meeting of agronomists.
Rules aimed at preventing the spread of the disease - which include creating "buffer zones" free of cocoa trees between each plantation - are regularly flouted, he said.
The disease has led to many farmers abandoning their plantations in Ivory Coast, said Klebe Boubacar, of the country's National Research Centre.
More than 70% of farms in Ivory Coast, which is one of the world's largest cocoa producers, are not being fertilized, Mr Boubacar added.