Climate Change Has Increased Risk of Devastating Banana Disease Black Sigatoka by Nearly 50 Percent

Bananas are one of the world's most important crops, but in recent decades, the plant has been severely affected by a devastating fungal disease known as Black Sigatoka.

And the problem looks set to get worse, as according to a study published in the journal Philosophical Transactions of the Royal Society B, climate change has increased the infection risk of this disease—the most damaging to affect a major tropical food plant—by nearly 50 percent in banana-growing areas of Latin America and Caribbean.

"Black Sigatoka is a fungal disease of bananas, which infects the leaves and reduces productivity of the plant," Daniel Bebber, author of the study from the University of Exeter in the U.K, told Newsweek. "The disease was imported to Honduras in 1972 from Asia, and is now present across Latin America and the Caribbean."

"It requires continual spraying with fungicides in affected regions," he said. As an example of the impact this has on farmers, "Costa Rican growers spray fungicides between 40 and 80 times per year, at a cost of $2,500 per hectare per year. This adds up to $100 Million for Costa Rica alone."

Bebber said he decided to investigate this issue because of his interest in understanding how plant pests and diseases are influenced by changing weather patterns.

"Black Sigatoka is a good example of a pathogen that is strongly influenced by weather, because it needs certain moisture and temperature conditions to infect the plant," he said. "So, it is a good candidate for studying this phenomenon."

Bananas are particularly vulnerable to such diseases because the variety that is exported around the world—the Cavendish—is genetically uniform.

Bebber came to his conclusions after combining experimental data on Black Sigatoka infections—which are caused by the fungus Pseudocercospora fijiensis—with detailed climate information from the past 60 years.

"The key finding is that Black Sigatoka infection risk increased by an average of 44 percent across the banana-growing areas of Latin America and the Caribbean since the 1960s, due to climate change," he said. Therefore, climate change has placed a greater burden on banana growers."

Bebber suggests that a significant factor behind this increased risk could be that climate change has made temperatures better for the spores of P. fijiensis to germinate and grow, while also making crop canopies wetter, in banana growing areas.

The fungus spreads via spores that are released into the air, infecting banana leaves, eventually leading to the development of characteristic streaked lesions and cell death when certain toxins are exposed to light.

However, the study also suggests that climate change is not the only factor behind the spread of Black Sigatoka, which can reduce the quantity of fruit produced by each plant by up to 80 percent. Increasing banana production and international trade also play an important role in this process.

Although the study found that, overall, the risk of infection increased in Latin America and the Caribbean, there were some areas—certain parts of Mexico and Central America, for example—where drier conditions have had the opposite effect

"The disease will get worse for regions that become wetter due to climate change," Bebber said. "However, while those areas that become drier in future may not suffer as much from the disease, the bananas themselves need plenty of water to grow. So, drying will be good for Black Sigatoka management, but will require much more careful water management in future."

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Bananas are on display at the "Central de Abasto" wholesale market in Mexico City on January 30, 2018. ALFREDO ESTRELLA/AFP/Getty Images
Climate Change Has Increased Risk of Devastating Banana Disease Black Sigatoka by Nearly 50 Percent | Tech & Science