Chocolate Under Threat from Old and New Cacao Diseases

<i>Theobroma cacao</i>, the source of chocolate, is affected by destructive diseases wherever it is grown. Some diseases are endemic; however, as cacao was disseminated from the Amazon rain forest to new cultivation sites it encountered new pathogens. Two well-established diseases cause the greatest losses: black pod rot, caused by several species of <i>Phytophthora</i>, and witches' broom of cacao, caused by <i>Moniliophthora perniciosa</i>. <i>Phytophthora megakarya</i> causes the severest damage in the main cacao producing countries in West Africa, while <i>P. palmivora</i> causes significant losses globally. <i>M. perniciosa</i> is related to a sister basidiomycete species, <i>M. roreri</i> which causes frosty pod rot. These <i>Moniliophthora</i> species only occur in South and Central America, where they have significantly limited production since the beginnings of cacao cultivation. The basidiomycete <i>Ceratobasidium theobromae</i> causing vascular-streak dieback occurs only in South-East Asia and remains poorly understood. Cacao swollen shoot disease caused by <i>Cacao swollen shoot virus</i> is rapidly spreading in West Africa. This review presents contemporary research on the biology, taxonomy and genomics of what are often new-encounter pathogens, as well as the management of the diseases they cause.