Leafcutter ant Atta bisphaerica

Taxonomic classification: Atta bisphaerica belongs to the order Hymenoptera, the family Formicidae, and the subfamily Myrmicinae. These ants are highly specialized social insects known for building massive underground colonies that can persist for many years and contain huge numbers of individual workers.

Crops affected: This species is a major agricultural pest, particularly in Brazil. It is known for its strong preference for Poaceae (grasses), including vital crops like maize, sugarcane, and various pasture grasses. Unlike some other leafcutter species that are generalists, Atta bisphaerica focuses heavily on grass vegetation, leading to severe economic losses.

Biology and life cycle: The survival of the colony depends on the cultivation of a symbiotic fungus, Leucoagaricus gongylophorus. The ants forage for leaf tissue not for direct consumption, but as a substrate to fertilize their subterranean fungus gardens. The queen, larvae, and workers depend entirely on this fungal food source, driving the incessant foraging activity.

Damage and severity: Workers use their sharp, serrated mandibles to cut plant material, often defoliating entire fields overnight. The damage results in reduced crop yields and destroyed pastures. Furthermore, their nesting behavior involves moving vast amounts of soil, which creates large mounds that interfere with agricultural machinery and can lead to root damage.

• Application of slow-acting toxic baits that are carried into the nest.
• Fumigation of the nest entrances and tunnels using approved insecticides.
• Mechanical disturbance of the nest structure to expose the queen to predation or chemicals.
• Integrated Pest Management (IPM) strategies to prevent colony establishment in fields.