Disease: witches' broomPathogen: Crinipellis perniciosaHost: cacao, Theobroma cacao
Witches' broom, caused by Crinipellis perniciosa, is found primarily in South America; although, it has also been reported in Panama and some Caribbean islands. This pathogen is a Basidiomycete fungus, and it produces pink, mushroom-like growths on infected trees. The fungus changes the physiological and hormonal relationships in the cacao tree causing it to grow clusters of succulent branches called brooms from flower clusters or other parts of the plant. It can also infect the cacao pods. Witches' broom reduced the Brazilian production of cocoa beans by 75% in less than ten years.
Image is from the APSnet Feature: The Impact of Plant Diseases on World Chocolate Production.