History
Witches' broom is a serious fungal disease of cacao in Latin America. A native of the Amazon, it is proliferating in most of the cacao
growing regions in South America as well as several Caribbean islands. Countries affected include Bolivia, Brazil, Colombia, Ecuador,
Grenada, Guyana, Panama, Peru, St. Vincent, Surinam, Tobago, Trinidad, and Venezuela. Witches' broom was discovered for the first time
in the state of Bahia, Brazil, in 1989 . It has since invaded the major growing area of Brazil and wreaked havoc on the cacao harvest.
Cocoa production in Bahia saw a decrease of 60% from 1990 to 1994.
Biology
During rainy seasons, basidiospores are spread by wind and must land in water to germinate and infect cacao. Seeds in developing cacao
pods that are infected up to 12 weeks of maturity are commonly destroyed and cocoa beans are not produced.
Ecology
The fungus Crinipellis perniciosa causes witches' broom. When the fungus takes hold, the tree will send up shoots from flower
clusters and branch tips and infect cacao pods. The ability of trees to produce pods filled with cacao beans is then severely reduced
by Witches' broom.
Impact
Historically, Brazil has exported ~$100 million in cacao beans to the United States annually and led to South America in exporting cacao.
Witches' broom has contributed to Brazil sliding to 8th place in cacao exports within 5 years. "Harvest and export to the United States of
Brazilian beans from Bahia have plummeted from 430,000 tons in 1985-86 to about 130,000 tons today. The major culprit is witches'-broom
disease," says John B. Lunde, director of international environmental programs for M&M Mars, Inc., of Hackettstown, New Jersey, one of the
world's largest chocolate manufacturers.
Control
The presence of witches' broom requires extensive knowledge and management of the local cacao crop. Knowledge of the plantation (tree
spacing, shade, proximity to neighboring diseased plantations, incidence and severity of witches' broom in the plantation, time of harvest,
pruning intensity) is vital to controlling the harvest.
References on the Web:
Ohio Agricultural Research & Development Center
Agricultural Research Service
Agricultural Research Service (photo)
