When maize screams, beans listen: How the Three Sisters crop trio repels pests
By Elizabeth Pennisi
For thousands of years small farmers in Mexico and parts of Central America have practiced a form of agriculture, known as milpa, that traces back to the ancient Maya. Tradition holds that mixing crops—typically maize, beans, and squash, the Three Sisters—in a single field improves yields. Scientists now know the beans fix nitrogen into the soil, enriching it for all plants; the maize stalks provide a structure for the beans to climb; and the squash covers the ground, suppressing weeds and keeping the soil moist. But researchers also suspected this “intercropping” has an additional benefit: helping decrease damage by plant pests.
New work, presented this month at the annual meeting of the Ecological Society of America in Los Angeles, suggests harm by pests is indeed reduced in these systems and that plant teamwork is responsible. By showing how the maize signals the beans to lure insects that eat their pests, the work could inspire other studies that might ultimately point to new ways for modern farmers to reduce pesticide use. But other work presented at the meeting suggested replicating the success of the Three Sisters may not be easy. Planting genetically different tomatoes together, a study showed, only protected them against pests when the set of varieties produced the right blend of volatile chemicals. “It is important which [crop variety] you are using,” says Patrick Grof-Tisza, a plant-insect ecologist at Converse University.
Science
By Elizabeth Pennisi
For thousands of years small farmers in Mexico and parts of Central America have practiced a form of agriculture, known as milpa, that traces back to the ancient Maya. Tradition holds that mixing crops—typically maize, beans, and squash, the Three Sisters—in a single field improves yields. Scientists now know the beans fix nitrogen into the soil, enriching it for all plants; the maize stalks provide a structure for the beans to climb; and the squash covers the ground, suppressing weeds and keeping the soil moist. But researchers also suspected this “intercropping” has an additional benefit: helping decrease damage by plant pests.
New work, presented this month at the annual meeting of the Ecological Society of America in Los Angeles, suggests harm by pests is indeed reduced in these systems and that plant teamwork is responsible. By showing how the maize signals the beans to lure insects that eat their pests, the work could inspire other studies that might ultimately point to new ways for modern farmers to reduce pesticide use. But other work presented at the meeting suggested replicating the success of the Three Sisters may not be easy. Planting genetically different tomatoes together, a study showed, only protected them against pests when the set of varieties produced the right blend of volatile chemicals. “It is important which [crop variety] you are using,” says Patrick Grof-Tisza, a plant-insect ecologist at Converse University.
Science