A rapidly spreading and devastating virus is posing an imminent threat to the health of cacao trees, which could potentially disrupt the world's supply of chocolate.
Cacao Swollen Shoot Virus Disease (CSSVD)
Tiny insects, known as mealybugs, consume trees' leaves, flowers, and buds. These bugs spread the devastating cacao swollen virus disease (CSSVD), a catastrophic threat to chocolate's root ingredient.
The virus is thought to be the most economically devastating virus disease in cacao. It is categorized under plant-infecting pararetroviruses from the Badnavirus. It is now known that CSSVD results from a complex species of Badnavirus based on the structure of its molecules.
CSSVD affects all the cacao plant's structures. Signs that can be observed on the tree's leaves include chlorotic vein flicking, red vein banding of the leaves, and different mosaic symptoms. It also results in swelling of the roots and the stems (tips, internodes, nodes). The pods of infected trees may become smaller, rounder, or have smoother surfaces. These symptoms can significantly reduce the quality and quantity of cacao produced, posing a serious threat to the global chocolate supply.
Some strains cause the pods to become smaller, rounder or have smoother surfaces.
Virus Threatens World's Chocolate Supply
The devastating virus has been attacking Ghana's cacao trees, leading to harvest losses equivalent to 15% to 50%.
Benito Chen-Carpentier, a mathematics professor at the University of Texas, Arlington, and an author of the study, underscores the real threat the virus poses to the global chocolate supply. He points out that pesticides are ineffective against mealybugs, forcing farmers to resort to drastic measures such as cutting infected trees and breeding resistant varieties. Despite these efforts, Ghana has lost over 254 million cacao trees.
While farmers can fight the bugs by vaccinating trees to inoculate them, this method has its limitations. Vaccines are expensive, especially for farmers with low wages, making them inaccessible to many. Moreover, vaccinated trees yield smaller quantities of cacao, which can further impact farmers' income. These challenges underscore the urgent need for a more cost-effective and efficient strategy to combat CSSVD.
Fighting CSSVD
Now, Chen-Charpentier and colleagues from the University of Kansas, the University of South Florida, Prairie View A&M, and the Cocoa Research Institute of Ghana have devised a novel strategy. This strategy uses mathematical data to determine how far apart farmers may plant vaccinated trees to prevent bugs from jumping across trees and spreading CSSVD. This innovative approach could significantly reduce the spread of the virus, helping to protect cacao trees and maintain the global chocolate supply. Findings were noted in the 'Cacao sustainability: The case of cacao swollen-shoot virus co-infection' study.
Chen-Charpienter explains that these bugs can move in several ways, such as moving across canopies, being transported by ants, or being blown by the wind. They had to develop a model to help cacao growers know how far away they should plant vaccinated trees from unvaccinated trees. This could help prevent viral spread while keeping the costs manageable.
The team has developed two model types that enable farmers to create a protective vaccinated tree layer surrounding unvaccinated ones. This innovative approach, though still in its experimental stage, holds promise for cacao growers. Chen-Charpentier explains that the models could help farmers keep their produce protected while helping them attain better yields. This could significantly reduce the economic impact of CSSVD and help to secure the global chocolate supply.
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