ScienceDaily (Apr. 12, 2009) — New diseases directly affect human survival and food security, especially as population density climbs. Leaf-cutting ants, one of a few groups of social insects to cultivate crops, have harvested plant material to fertilize their underground fungal gardens for ~50 million years. New results from the Smithsonian show that both the ants and their fungal crop actively combat fungi coming into the nest inside leaves, thus ensuring the health of their mutualism.

"When you look at a healthy tropical plant, you think you're seeing just one organism, but each leaf can have dozens of fungal species growing inside, some of which may protect the plant by excluding pathogens," explains Sunshine Van Bael, post-doctoral fellow at the Smithsonian Tropical Research Institute. The fungi growing inside leaves without causing disease to the plant are called endophytes: endo-, inside, and –phyte, plant.