The Chira Valley in Peru – one of the main regions for the cultivation of organic bananas – is being seriously affected by the dreaded Fusarium wilt. Once this disease (also known as Panama disease) has established itself on a plantation, it takes decades before Cavendish bananas or any other banana varieties prone to Fusarium can be grown there again. Wageningen University & Research and its partners are therefore taking a multi-pronged approach to solving the problem, using rapid detection, new varieties and new cultivation methods.
“There are 8,000 smallholders in the Chira Valley growing organic bananas on around 10,000 hectares of land. The region produces 25 percent of the global supply of organic bananas. The presence of Tropical Race 4 (TR4) – one of the Fusarium soil fungi that cause Fusarium wilt – is therefore very worrying,” says Gert Kema, professor of phytopathology and the team lead for the project to find solutions.
At present, there’s no way to combat this species of Fusarium. Once it strikes, the crop is ruined and the soil is contaminated, making it unfit for banana cultivation for years to come. “The strain originated in Southeast Asia, but has spread to 16 new countries over the past decade,” he says.
Rapid detection is crucial
Rapid detection of new infections can slow down their spread. Scientists at Wageningen have already developed a rapid test for use in the field. It takes less than an hour for the test to identify an infection.
“We’re now working on a system for mapping areas deemed to be at risk. The Chira Valley is serving as a case study for this. The only way to do it is from the air. It’s a large region, and there are parts we can’t physically access or get permission to access. So that’s why we carried out 12 flights in a small aircraft, and took 133,700 aerial photographs which we then analysed,” says Kema.
The whole region is reliant on a single irrigation system. Some areas are also prone to flooding. Fusarium can be spread through water, which is why the region is vulnerable to it. “We mapped the flood-prone areas and started taking samples in the field. This revealed that there were already more than 200 instances of Fusarium infection. That’s very worrying,” says Kema.
And growers don’t really have many options for containing the disease, he adds. They cut down infected plants, but it’s not enough. “Once you can see it, it’s already too late. It’s almost impossible to control it at that point.”
Monoculture of a single variety
The arrival of the disease in this region is a major setback. With its dry conditions, the region is perfect for organic banana farming. It means that the other dreaded banana disease, Black Sigatoka, isn’t a problem here. That disease is caused by a leaf mould, and the conventional banana sector already relies on high and ever-increasing doses of anti-fungal agents to tackle it.
The reason these two fungal diseases are such a problem is largely because banana production around the world is dominated by a single variety: the Cavendish. Wageningen University & Research partners with Yelloway, the venture of Chiquita, KeyGene and MusaRadix, to develop new varieties that are resistant or more resilient to the fungi. Kema expects these to be available by 2028.
But time is running out. Fusarium is spreading. “In the Philippines, thousands of hectares have now been written off. They won’t be growing a Cavendish there for decades to come. That’s how long the fungus maintains a reservoir in soil and weeds,” says Kema.
A new cultivation system is therefore being developed: banana plants grown in containers on an organic substrate. This now seems to be a realistic option for the hardest-hit areas. “Abandoning soil altogether really is a solution. It may even lead to increased productivity.”