Potato farmers beat a devastating worm with paper made from bananas » El Horticultor

Potato cyst nematodes are an intelligent pest. These microscopic worms travel through the soil, burrowing into the roots of young potato plants and cutting crops by up to 70%. It’s also hard to get rid of: the eggs are protected inside the mother’s body, which hardens after death into a cyst that can survive in the ground for years.

However, researchers have shown that a simple paper bag created from banana fibers disrupts the hatching of cyst nematodes and prevents them from finding potato roots. The new technique increased yields fivefold in trials with smallholder farmers in Kenya, where the pest recently invaded, and could significantly reduce the need for pesticides. The strategy can also benefit other cultures.

“This is important work,” says Graham Thiele, research director at the International Potato Center. However, “there is still a lot of work to do to move from a good find to a real solution for farmers in East Africa”, he warns.

Soil nematodes are a problem for many types of crops. For potatoes, the golden cyst nematode (Globodera rostochiensis) is a global threat. Plants with infected and damaged roots have yellowed and wilted leaves. Their potatoes are smaller and often covered in lesions, making them unsaleable. In temperate countries, the worms can be controlled by rotating potatoes with other crops, spraying the soil with pesticides and planting varieties selected to resist infection.

Potato farmers beat a devastating worm with paper made from bananas

These approaches are not yet feasible in many developing countries, in part because pesticides are expensive and resistant potato varieties are not available for tropical climates. Moreover, small farmers, who can earn decent money selling potatoes, are often reluctant to rotate their crops with less valuable crops.

In Kenya, the potato cyst nematode has expanded its range and flourished. “Nematode densities are incredibly high,” says Danny Coyne, a nematode expert at the International Institute of Tropical Agriculture. This creates an additional problem of biodiversity loss: potato growers cut down forests to create new nematode-free fields.

The idea that banana paper could help farmers rid their soil of nematodes was born more than 10 years ago. Researchers at North Carolina State University (NC State) were looking for a way to help farmers in developing countries safely administer small doses of pesticides. They experimented with various materials. They have found that what works best is the paper made from banana trees. Its tubular, porous fibers slowly release pesticides into the soil for several weeks before breaking down. By this time, the plant has grown enough that, even if it is infected, it already has a healthy root system.

In a field trial, the researchers added abamectin, a pesticide that kills roundworms, to the paper. They also planted potatoes on banana paper without abamectin as a control. To their surprise, these plants grew almost as well as those that had pesticides on them. Coyne mentioned this puzzling finding to a colleague, a chemical ecologist named Baldwyn Torto who studies pest-plant interactions at the International Center for Insect Physiology and Ecology. “It’s really fascinating,” recalls Torto.

Along with Juliet Ochola, now a graduate student at NC State, Torto designed several experiments to find out what was going on. The duo discovered that plantain paper retains key compounds released by the roots of young potato plants, some of which attract soil microbes that benefit the plant. Nematodes have also evolved to detect these compounds. Some, like alpha-chaconine, are a signal for the hatching of nematode eggs. “If a lot of them hatch at the same time, they can rupture the cysts,” says Ochola. After hatching, the young nematodes detect the compounds and use them to search for the tender roots of the potato.

Banana fibers absorbed 94% of the compounds, Ochola and his colleagues found. When they exposed nematode eggs to exudates using the paper, the hatch rate decreased by 85% compared to not using the paper, the team reports today in Nature Sustainability. Other experiments have suggested that hatching nematodes are much less likely to find potato roots encased in paper.

In nematode-infested fields in Kenya, Coyne and colleagues showed that planting potatoes wrapped in banana paper tripled the harvest compared to planting without paper. A small dose of abamectin in the paper, just five thousandths of what is normally sprayed on the ground, increased yield by another 50%. Abamectin likely killed all nematodes found on potatoes. “We have a win here,” Coyne said.

Now researchers are trying to figure out how to supply wrapping paper to potato farmers in East Africa. Banana plantations in Kenya and neighboring countries could provide the fibers, which are now disposed of as waste. The papermakers could then manufacture the bags. Coyne suspects the biggest challenge will be convincing farmers to buy the paper for the first time.

Once farmers try the bags, they will find them easy to use, the researchers say. “It’s just wrap and plant”said Ochola. Simple, yes, but packing lots of potatoes will always be laborious, says Isabel Conceição, a nematode expert at the University of Coimbra. If a machine for packing potatoes is developed, he says, the approach may also be feasible on large farms that use mechanical seeders.

Meanwhile, Coyne and his colleagues say they have had encouraging results from trials with other root crops, such as yams and sweet potatoes. He also hopes that many types of vegetables, planted as seeds or seedlings, can be protected from pests and soil pathogens with small banana fiber pots or trays, impregnated with various pesticides or biological control agents.

The appeal is natural: banana paper is biodegradable, recycled from waste and could help protect both farmers and the environment. “We are reducing the amount of pesticides a lot,” says Ochola. “To me, I feel like it’s amazing.”

Source: https://www.science.org/content/article/potato-farmers-conquer-devastating-worm-paper-made-bananas

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