![]() Presumably, any nematodes that happened to come across the potatoes were then killed by the abamectin. A tiny dose of abamectin in the paper-just five-thousandths of what would normally be sprayed on the soil-boosted the harvest by another 50%. ![]() In nematode-infested fields in Kenya, Coyne and colleagues showed planting potatoes wrapped in plain banana paper tripled the harvest compared with planting without the paper. Other experiments suggested the nematodes that do hatch are far less likely to be able to find potato roots enclosed in the paper. When they exposed nematode eggs to the exudates using the paper, the hatching rate decreased by 85% compared with not using the paper, the team reports today in Nature Sustainability. After hatching, the young nematodes sense the compounds and use them to seek out the tender potato roots.īanana fibers absorbed 94% of the compounds, Ochola and colleagues found. “If a lot of them hatch at the same time, they’re able to bust open the cysts,” Ochola says. Some, such as alpha-chaconine, are a signal for nematode eggs to hatch. Nematodes have also evolved to notice these compounds. The duo discovered the banana paper holds onto key compounds released from the roots of young potato plants, some of which attract soil microbes that benefit the plant. Together with Juliet Ochola, now a graduate student at NC State, Torto devised several experiments to figure out what was going on. “This is fascinating indeed,” Torto recalls thinking. Coyne mentioned this puzzling result to a colleague, a chemical ecologist named Baldwyn Torto who studies the interactions between pests and plants at the International Centre of Insect Physiology and Ecology. To their surprise, those plants grew nearly as well as the ones with pesticides. They also planted potatoes in banana paper without abamectin as a control. In a field trial, researchers added abamectin, a pesticide that kills nematodes, to the paper. By then, the plant has developed enough so that even if it does get infected, it already has a healthy root system. Their tubular, porous fibers slowly release pesticides in the soil for several weeks before breaking down. What works best, they found, is paper made from banana plants. They experimented with various materials. Researchers at North Carolina State University (NC State) were looking for a way to help farmers in developing countries safely deliver small doses of pesticides. The idea that banana paper could help farmers rid their soil of nematodes was hatched more than 10 years ago. This is leading to an additional problem of biodiversity loss: Potato farmers are cutting down forests to create new fields free of the nematodes. “The nematode densities are just so astonishingly high,” says Danny Coyne, a nematode expert at the International Institute of Tropical Agriculture. In Kenya, the potato cyst nematode has expanded its range and thrived. In addition, small-scale farmers, who can make decent money selling potatoes, are often reluctant to rotate their planting with less valuable crops. These approaches aren’t yet feasible in many developing countries, in part because pesticides are expensive and resistant varieties of potatoes aren’t available for tropical climates. In temperate countries, worms can be controlled by alternating potatoes with other crops, spraying the soil with pesticides, and planting varieties bred to resist infection. ![]() Their potatoes are smaller and often covered with lesions, so they can’t be sold. Plants with infected, damaged roots have yellowish, wilting leaves. ![]() For potatoes, the golden cyst nematode ( Globodera rostochiensis) is a worldwide threat. Soil nematodes are a problem for many kinds of crops. But, “There’s still quite a lot of work to take it from a nice finding to a real-life solution for farmers in East Africa,” he cautions. “It’s an important piece of work,” says Graham Thiele, a research director at the International Potato Center who was not involved with the study. The strategy may benefit other crops as well. The new technique has boosted yields fivefold in trials with small-scale farmers in Kenya, where the pest has recently invaded, and could dramatically reduce the need for pesticides. Now, researchers have shown a simple pouch made of paper created from banana tree fibers disrupts the hatching of cyst nematodes and prevents them from finding the potato roots. They are challenging to get rid of, too: The eggs are protected inside the mother’s body, which toughens after death into a cyst that can survive in the soil for years. These microscopic worms wriggle through the soil, homing in the roots of young potato plants and cutting harvests by up to 70%. ![]()
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