Moniliophthora perniciosa
Encyclopedia
Moniliophthora perniciosa (previously Crinipellis perniciosa) is a fungus
that causes "Witches' Broom
Disease" (WBD) of the cocoa tree (Theobroma cacao). This pathogen is currently limited to South America, Panama and the Caribbean, and is perhaps one of the best-known cocoa diseases, thought to have co-evolved with cocoa in its centre of origin (first recorded in the Brazilian Amazon
in 1785). In 1989, it was introduced to the cocoa producing state of Bahia
of Brazil
, where output diminished from 380,000 tonnes per annum to 90,000 tonnes in the late 1990s. Brazil went from being the world’s second largest cocoa producer to becoming a net importer. Unlike frosty pod rot
, which is highly infectious but mostly destructive to pods, WBD can infect many sites on actively-growing trees, throughout the growing season, and in severe cases can cause tree death.
It exists in two characteristic phases: biotrophic (expanding and infecting) and saprotrophic (dying, and producing spores). The biotrophic stage, and what triggers its switch to a saprotrophic stage, are still not understood.
The spores of this fungus are spread by wind, but must land in water in order to germinate
. As a consequence, it mainly spreads during rainy periods. Control is very difficult, and requires extensive work to remove. The most critical part of treatment (pruning
of diseased material) can only be conducted during dry periods, or one risks spreading the disease further. Due to economics, most discarded brooms are usually left on the ground, leaving a risk of reinfection of trees the subsequent year. However, spraying the ground with a light coating of oil
can prevent the spores from becoming airborne again.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
that causes "Witches' Broom
Witch's broom
A Witch's broom is a disease or deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird's nest....
Disease" (WBD) of the cocoa tree (Theobroma cacao). This pathogen is currently limited to South America, Panama and the Caribbean, and is perhaps one of the best-known cocoa diseases, thought to have co-evolved with cocoa in its centre of origin (first recorded in the Brazilian Amazon
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
in 1785). In 1989, it was introduced to the cocoa producing state of Bahia
Bahia
Bahia is one of the 26 states of Brazil, and is located in the northeastern part of the country on the Atlantic coast. It is the fourth most populous Brazilian state after São Paulo, Minas Gerais and Rio de Janeiro, and the fifth-largest in size...
of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, where output diminished from 380,000 tonnes per annum to 90,000 tonnes in the late 1990s. Brazil went from being the world’s second largest cocoa producer to becoming a net importer. Unlike frosty pod rot
Moniliophthora roreri
Moniliophthora roreri is a plant pathogen of Herrania and Theobroma spp., including the cacao tree: on which it is called Frosty pod rot. T. gileri thought to be the indigenous forest host in the upper Amazon basin. Sometimes it is known by the misnomer Monilia...
, which is highly infectious but mostly destructive to pods, WBD can infect many sites on actively-growing trees, throughout the growing season, and in severe cases can cause tree death.
It exists in two characteristic phases: biotrophic (expanding and infecting) and saprotrophic (dying, and producing spores). The biotrophic stage, and what triggers its switch to a saprotrophic stage, are still not understood.
The spores of this fungus are spread by wind, but must land in water in order to germinate
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
. As a consequence, it mainly spreads during rainy periods. Control is very difficult, and requires extensive work to remove. The most critical part of treatment (pruning
Pruning
Pruning is a horticultural practice involving the selective removal of parts of a plant, such as branches, buds, or roots. Reasons to prune plants include deadwood removal, shaping , improving or maintaining health, reducing risk from falling branches, preparing nursery specimens for...
of diseased material) can only be conducted during dry periods, or one risks spreading the disease further. Due to economics, most discarded brooms are usually left on the ground, leaving a risk of reinfection of trees the subsequent year. However, spraying the ground with a light coating of oil
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
can prevent the spores from becoming airborne again.