Photo worth seeing: New protection for cocoa trees

Cocoa tree
This cocoa tree is still healthy. But a virus could soon change this. © University of Texas Arlington

The beans of a cocoa plant produce the ever-popular chocolate. However, a virus is currently making many cocoa plants sick. What to do?

Since the first cocoa beans were brought to Europe by the Spaniard Hernan Cortés in the 16th century, cocoa has enjoyed great popularity around the world. In Germany alone, several hundred thousand tons of chocolate and chocolate products are produced every year from imported cocoa beans. The cocoa plant originally comes from areas in the Amazon, from where the seeds came to Central America. The plant is now grown in tropical areas in Africa, Asia, Central and South America. The majority of the harvest comes from countries in West Africa, especially Ivory Coast and Ghana.

However, this cocoa crop is at risk from the rapidly spreading virus Cacao Swollen Shoot Virus Disease (CSSVD). The virus is transmitted by mealybugs that feed on the leaves, buds and flowers of the cocoa tree. The CSSVD attacks the cocoa plant and its seeds and can lead to crop losses of between 15 and 50 percent. Infected trees usually die within a few years.

Pesticides are often used to protect plants from pest infestation. However, these remedies do not work well on mealybugs. Instead of cutting down the infected trees, farmers also have the option of vaccinating the cocoa plants against the virus. However, this method is expensive and results in a smaller harvest, so not every farmer can implement it.

Researchers at the University of Kansas have now developed a strategy to help contain the spread of the virus through mealybugs. Using mathematical models, they calculate the minimum distance between the cocoa trees and each other in order to prevent the mealybugs from crossing over and thus also the transmission of the virus. Vaccinated trees could form an additional protective barrier around the infected trees. This method is intended to keep costs low for small farmers and help maintain the health of the cocoa plants. A still healthy specimen can be seen in the photo.

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