The global chocolate crisis: How can we save the dying cocoa trees?

Compiled by: Gong Zixin

chocolate--

The world's most popular cuisine

Facing a supply crisis

Did you know?

About 50% of the world's chocolate

Cocoa trees from the West African countries of Ivory Coast and Ghana

However

A rapidly spreading, destructive virus

The attack on Ghana's cocoa trees

15% to 50% harvest loss

The surprising thing is

Recently

Researchers developed a new strategy

Can inhibit the spread of viruses

The virus, called cocoa swollen bud virus disease (CSSVD), is spread by tiny insects called mealybugs (Pseudococcidae, Homoptera) that eat leaves, buds and flowers and are one of the most destructive threats to the root ingredient of chocolate. Infection occurs when mealybugs pick up viruses from infected cocoa or other host plants and deposit them in healthy cocoa trees during feeding.

"This virus poses a real threat to the global chocolate supply," said Benito Chen-Charpentier, a professor of mathematics at the University of Texas at Arlington and author of "Cocoa Sustainability: The Case of Swollen Bud Virus Co-infection," published in the journal PLOS ONE. "Pesticides are not very effective against mealybugs, and farmers can only prevent the spread of the disease by cutting down infected trees and breeding insect-resistant trees. But despite these efforts, Ghana has lost more than 254 million cocoa trees in recent years."

Farmers can combat mealybugs by vaccinating trees to protect them from the virus, but vaccines are expensive, especially for low-income farmers, and vaccinated trees produce lower yields, exacerbating the damage done by the virus.

Chen-Charpentier and colleagues developed a new strategy: using mathematical data to determine how far apart farmers can plant vaccinated trees to prevent mealybugs from jumping from tree to tree and spreading the virus.

“Mealybugs can move in several ways, including from one canopy to another, carried by ants or blown by the wind,” Chen-Charpentier said. “What we need to do is create a model for cocoa farmers so they can know how far to plant vaccinated trees from unvaccinated trees to prevent the spread of the virus while keeping costs manageable for these smallholder farmers.”

By experimenting with mathematical modelling techniques, the team created two different types of models that allowed farmers to create a protective layer of vaccinated cocoa trees around unvaccinated cocoa trees.

Chen-Charpentier stressed that while these models are still in the experimental stage, they will help farmers protect their crops while helping them to get better harvests, which will also benefit our global addiction to chocolate.