Cameroon's chief cocoa-growing region has been hit by an outbreak of black-pod disease, destroying large areas of the African country's main crop.
The disease, caused by a fungus whose spores spread rapidly in humid conditions, has been exacerbated by large amounts of rainfall which causes rotting in infected plants.
Cameroon is the world's fifth largest producer of cocoa after Cote d'Ivoire, Ghana, Indonesia, and Nigeria, and the country's south-west province where the disease has struck, accounts for more than 50% of its annual harvest.
The country also suffers from poor crop management, with many cocoa trees now past the age of prime production being left unreplaced.
Samuel Mbonombo, a farmer who heads a big cocoa farmers' group, told Dow Jones Newswires: "Almost every cocoa farm in the South-West region is infested by black-pod disease. Between 5% and 6% of the current production may be destroyed."
Prices for the chocolate ingredient have remained fairly stable this year - down just 1.1% year to date, as crop forecasts in the top producing countries Cote d'Ivoire and Ghana have been good.
In the last few weeks, however, prices have been moving higher after reports of rejected Ecuadorian cargoes at US ports due to contamination. Prices are currently at seven-month highs.
Cameroon's likely drop in production was not expected to have a major impact on total global production this year, but the cocoa price was lifted on Monday, up 0.2% to $2,131 a tonne.