Climate change is helping spread a fungus that attacks bananas

A fungal plant disease from Asia has been spreading across banana-growing areas of Latin America and the Caribbean since the 1960s. New research suggests that climate change is aiding the spread of this highly destructive plant infection.

Black sigatoka, commonly known as “black leaf streak,” can reduce the fruit produced by infected plants by up to 80%, according to a study published Monday in the biology journal, Philosophical Transactions of the Royal Society B.

“The disease is a fungus,” Dan Bebber, study author and a senior lecturer in microbial ecology at the University of Exeter, told CNN. “It attacks the leaves of the banana plant, which means the plant can’t make as many bananas.”

First reported in Honduras in 1972, black sigatoka has since spread throughout the region, arriving in Brazil in 1998 and the Caribbean islands of Martinique, St. Lucia and St. Vincent and the Grenadines in the late 2000s. In August 2004, black sigatoka made its first appearance in Puerto Rico.

The disease now occurs as far north as Florida, the study indicates.

The fungal disease is virulent against a wide range of banana plants and increases production costs with fungicide necessary to maintain crop yields, according to the US Department of Agriculture. “Currently, the disease is controlled by fungicide sprays. Banana growers in Costa Rica, for example, have to spray 40 to 80 times per year,” said Bebber. “This is very expensive, costing the country around $100 million per year.”

Climate change is known to significantly alter the distribution of species in the wild, yet plant responses to historical climate change are poorly understood. The new study combined experimental data on black sigatoka infections with detailed climate information over the past 60 years to understand how rapidly the spread has occurred in Latin America and the Caribbean.

What did the model show? Infection risk has increased by 44.2% on average across banana-growing areas of Latin America and the Caribbean since the 1960s through the current decade. This was due to greater wetness plus altered temperature conditions favorable to the pathogen.

While increasing banana production and global trade have probably facilitated black sigatoka’s establishment and spread, climate change has made the region increasingly conducive for plant infection, Bebber and his co-authors wrote in the study.

“We don’t know exactly what will happen in future,” Bebber told CNN. In places where the climate gets wetter, the disease will get worse, but in places that get drier over time, the disease won’t be as bad, though there careful water management will be needed since bananas are “thirsty plants.”

In short, bananas and the plethora of foods that make us happy — banana breads, pies, cereals and puddings — will not disappear from the Earth, but they certainly may become more difficult to cultivate and also more expensive for consumers.

“Our main message is that bananas are expensive to produce but cheap for us to buy,” said Bebber. “It’s important that we pay a fair price for bananas, so that growers can invest in sustainable production and research to make sure we can continue to enjoy them in the future.”

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