Vast quantities of leaves are needed to feed such large ant colonies, and this leads to massive destruction of vegetation.
Leaf-cutting ants in tropical countries are essential to recycling plant material and to keeping the soil aerated as earthworms do in more temperate climates. However, they are a menace to humans who try to farm in tropical regions of the New World (Angier, 1994). Leaf-cutting ants are the dominant herbivore in the Neotropics, consuming about 20 percent of all the fresh-leaf biomass there. Ants are the main reason it is difficult to develop agriculture in the Neotropics. Most of the plants native to the Neotropics have evolved sufficient defenses that they are not entirely torn apart by the attine ants, but when farmers try to bring in crops foreign to the area - such as fruit trees from California or Africa - the results are disastrous. The ants will strip entire orchards of leaves in no time.
Traditionally, the fungal gardens of the ants were thought to be free of microbial parasites
...