It is from the seeds of the cocoa tree that chocolate is produced. About half of the world’s chocolate it comes from trees in Ghana and Ivory Coast, in West Africa, where the virus is spreading rampant.
The virus is causing crop losses of up to 50%, due to its spread by small insects carrying the virus. These insects, called mealybugs, eat the flowers, buds and leaves of cocoa trees. Through the wind or transported by ants, mealybugs can migrate from tree to tree and from canopy to canopy, thus spreading the disease “cocoa swollen shoot virus”.
“This virus is a real threat to the global chocolate supply,” said Benito Chen-Charpentier, professor of mathematics at the University of Texas at Arlington and co-author of a recent study published in PLOS One titled: “Cacao sustainability: The case of cacao swollen-shoot virus co-infection.”
What can be done against the virus that infests cocoa?
In theory, farmers can fight the spread of the virus by mealybugs giving trees vaccines that protect them from the virus. But these vaccines are faces, especially for farmers who earn low wages. Furthermore, trees that are vaccinated produce less cocoa for the harvest, which makes the situation worse for farmers and the global cocoa supply.
Unfortunately, pesticides are not a solution either to keep mealybugs away. “Pesticides don’t work well against mealybugs, which leads farmers to try to stop the spread of the disease by cutting down infected trees and breeding resistant trees. But despite these efforts, Ghana has lost more than 254 million cocoa trees in recent years.” .
There is still hope, and it emerges from the work of Chen-Charpentier and her team at the University of Kansas Cocoa Research Institute, Ghana, Prairie View A&M and the University of South Florida.
Published in PLOS One, they designed a new strategy for using mathematical data to deduce the distance at which farmers can plant vaccinated trees so that mealybugs cannot jump between them and spread the virus.
Formation of a “shield” of trees against invaders
The team identified a strategic model with a area of vaccinated cocoa trees which should add protection as a barrier in front of unvaccinated trees. Their steps were experimental, but the models resulting from the recently published study can be implemented to help farmers protect their crops in order to obtain a constant cocoa harvest.
The models haven’t yet been tested “in the real world,” but if they work, it won’t just be good news for the economic stability of cocoa producers, but also for the global supply of chocolate.
News reference:
Agusto FB, Leite MCA, Owusu-Ansah F, Domfeh O, Hritonenko N, Chen-Charpentier B (2024). Cacao sustainability: The case of cacao swollen-shoot virus co-infection. PLOS ONE.
