Scarcity, higher prices forecast
By UNIVERSITY OF TEXAS AT ARLINGTON
New
strategies, including costly vaccines and mathematical models to optimize tree
planting, are being developed to combat this threat.
The cacao swollen shoot virus disease can result in the
loss of up to 50% of certain harvests.
A swiftly spreading virus poses a risk
to the health of cacao trees and the dried seeds used to make chocolate,
putting the worldwide supply of this beloved treat at risk.
About 50% of the world’s chocolate originates from cacao trees in the West Africa countries of Ivory Coast and Ghana. The damaging virus is attacking cacao trees in Ghana, resulting in harvest losses of between 15 and 50%.
Spread by small insects called mealybugs that eat the leaves, buds,
and flowers of trees, the cacao swollen shoot virus disease (CSSVD) is among
the most damaging threats to the root ingredient of chocolate.
“This virus is a real threat to the global supply of chocolate,” said Benito Chen-Charpentier, professor of mathematics at The University of Texas at Arlington and an author of “Cacao sustainability: The case of cacao swollen-shoot virus co-infection” in the journal PLoS One.
“Pesticides don’t work well against
mealybugs, leaving farmers to try to prevent the spread of the disease by
cutting out infected trees and breeding resistant trees. But despite these
efforts, Ghana has lost more than 254 million cacao trees in recent years.”
Farmers can combat the mealybugs by giving vaccines to
the trees to inoculate them from the virus. But the vaccines are expensive,
especially for low-wage farmers, and vaccinated trees produce a smaller harvest
of cacao, compounding the devastation of the virus.
Mathematical Modeling to Aid Farmers
Chen-Charpentier and colleagues from the University of
Kansas, Prairie View A&M, the University of South Florida, and the Cocoa
Research Institute of Ghana have developed a new strategy: using mathematical
data to determine how far apart farmers can plant vaccinated trees to prevent
mealybugs from jumping from one tree to another and spreading the virus.
“Mealybugs have several ways of movement, including moving from canopy to canopy, being carried by ants or blown by the wind,” Chen-Charpentier said.
“What we needed to do was create a model for cacao
growers so they could know how far away they could safely plant vaccinated
trees from unvaccinated trees in order to prevent the spread of the virus while
keeping costs manageable for these small farmers.”
By experimenting with mathematical patterning techniques,
the team created two different types of models that allow farmers to create a
protective layer of vaccinated cacao trees around unvaccinated trees.
“While still experimental, these models are exciting
because they would help farmers protect their crops while helping them achieve
a better harvest,” Chen-Charpentier said. “This is good for the farmers’ bottom
line, as well as our global addiction to chocolate.”
Reference: “Cacao sustainability: The case of cacao
swollen-shoot virus co-infection” by Folashade B. Agusto, Maria C. A. Leite,
Frank Owusu-Ansah, Owusu Domfeh, Natali Hritonenko and Benito Chen-Charpentier,
7 March 2024, PLOS ONE.
DOI: 10.1371/journal.pone.0294579
The study was funded by Aim Square, the University of
Kansas, the U.S. National Science Foundation, the Basque Center for Applied
Mathematics, and Prairie View A and M University.
