Potential Chocolate Shortage May Be Foiled by Beneficial Fungi

By Hank Becker
October 25, 1999

WASHINGTON, Oct. 25--U.S. Department of Agriculture scientists are working with a team of international experts to save the chocolate crop from three pathogenic fungi, Agricultural Research Service Administrator Floyd Horn said today. Chocolate is produced from the beans of the tropical cacao tree, Theobroma cacao.

"Three major fungal diseases can make cacao beans inedible or unusable," said Horn. "But scientists at USDA's Agricultural Research Service have identified and are testing beneficial fungi that control the bad fungi." The international effort coordinated by ARS includes the American Cocoa Research Institute, McLean, Va.; M&M Mars, Inc., Hackettstown, N.J.; and several international research groups. ARS is the chief research agency of the U.S. Department of Agriculture.

Fungal diseases--black pod rot, frosty pod rot and witches' broom--have caused severe yield losses to the cacao bean crop, which totaled almost 3 million tons in 1999. "The diseases cause economic hardship for 5 to 6 million small farmers in South America, Africa and Asia," Horn said. "Plus, few people realize that transforming cacao beans into chocolate is among the largest industries in support of U.S. agriculture."

For every dollar of U.S. cacao imports, about $1.50 in other agricultural commodities is used to make chocolate confections, according to the American Cocoa Research Institute.

"The fungus problem threatens the long-term health of the world's chocolate industry. But the research provides hope for small cacao farmers--and environmentalists concerned about the loss of cacao agroforests," Horn said.

Brazil annually exports about $100 million worth of cacao beans to the U.S. and traditionally has been the top South American cacao exporter. But witches' broom and other problems have made Brazil slip to eighth place in the past 5 years, according to John B. Lunde, director of international environmental programs for M&M Mars.

To help solve the fungal problems, plant pathologist Robert D. Lumsden at ARS' Biocontrol of Plant Diseases Laboratory, Beltsville, Md., is working with M&M Mars microbiologist Prakash K. Hebbar as part of a cooperative research project in which 10 national and international research institutes participate.

Several years ago, Lumsden and colleagues at the Beltsville lab developed methods to mass-produce beneficial fungi to combat plant disease. Their earlier research on the Trichoderma virens fungus led to its development as a commercial product, SoilGard, marketed to control several diseases of greenhouse, fruit and vegetable crops.

"Chemical controls for the fungi that attack cacao beans don't work very well and are expensive," Lumsden noted. "But cultivars tolerant of the fungal diseases are largely unidentified or have not been propagated in sufficient quantities."

In the first year of field trials in Peru, the scientists used simple garden sprayers to spray a mix of five different strains of locally isolated Trichoderma on flowers and pods of trees infected with frosty-pod disease, Peru's main cacao disease. "The mix of five biocontrol strains increased pod yields even more than strains used alone," Lumsden said.

At the Mars' Almirante Cocoa Research Center in Brazil, researchers are trying two new species of Brazilian isolated Trichoderma in lab trials and small field tests. "One species, called T. stromaticum, reduced pod infection by the witches' broom fungus by 31 percent," said Lumsden. ARS scientists are investigating how this Trichoderma species works and seek more economical methods for mass-producing it. "This would make it easier and more cost-effective for small farmers to use," he said.

Lumsden said the researchers' goal is to identify natural controls for use in integrated pest management systems. The IPM systems would also use fungus-resistant cacao lines and cultural practices that encourage sustainable cacao cultivation in the natural forest ecosystem.

Each year, U.S. chocolate manufacturers use about 250,000 tons of dry milk, 400,000 tons of sugar and 350,000 tons of peanuts. In 1997, the U.S. industry used more than $3 billion worth of these and other U.S. agricultural products. The U.S. exports over $600 million worth of chocolate products a year.

A story about the research will appear in the November issue of ARS' Agricultural Research magazine.

Scientific contact: Robert D. Lumsden, ARS Biocontrol of Plant Diseases Laboratory, Beltsville, Md., phone (301) 504-5682, fax (301) 504-5968, rlumsden@asrr.arsusda.gov and phebbar@asrr.arsusda.gov.