Everton, in Colombia we use an Integrated Pest Management Strategy to control de Leafcutting ants (Atta cephalotes and related species). First the measurement of the nest is essential to determine the most appropriate type of control to perform and calculate the amount of product needed.The manual control is used only for small nests within the first three months, between the bridal flight and the opening of the first orifice. The manual destruction of the nest and the queen is done by using a shovel or pin, since the chamber is only 20-30 cm deep. Chemical control with powdered formicides for small and medium-sized nests through the use of the insufflator so that the product penetrates into the chambers. Do not apply the dust on the roads because it only controls the ants in transit, but do not eliminate the anthill, besides it contaminates the soil. For large nests, the thermo- fogg Generator are useful using a dose of 50 cm3 of chlorpyrifos per liter of ACPM (Diesel Fuel) at the rate of one minute of thermospray per 10 m2 of nest. Toxic baits, in the form of a pellet based on sulfluramide, avamectin or fipronil. Use 8 to 10 grams per square meter of nest. They should be applied on dry days and with gloves, placed in mounds on the side of the road near the forage mouth so that the workers load them up to the nest. Never apply inside the nest. Likewise, biological control using baits based on entomopathogenic fungi such as Metarrhizium anisopliae and Beauveria bassiana and antagonists such as Trichoderma lignorum contaminate the symbiont fungus Leucoagaricus gongylophorus of the leafcutting ant, causing the death of the colony. For more information on this subject please see: La Hormiga Arriera Atta cephalotes (Hymenoptera:Formicidae) In: Bustillo A.E (Ed.) Pp: 323-329. Los Insectos y su manejo en la Caficultura Colombiana. 2008. Cenicafé. Chinchiná. 488 p.

Is there the possibility of a systemic fungicide (if the crop value justifies it) to target the ant fungus gardens?

First thank you for your answer!

I found a different idea with no publications in the quick research I did.

Ants have several defense mechanisms to inhibit the occurrence of competing fungi (eg Escovopsis) that negatively influence the growth of the fungus they use as food (Leucogaricus). Therefore, when they carry something inside the nest, something abnormal is detected that compromises the development of their food fungus, they return what was carried outside the nest and this "memory" may last for a few months until every colony is renewed by new individuals.

My other fear about the technique mentioned is the economic issue, combined with the systematicity and residual required to be effective, but we will only know if to test.

Everton, in Colombia we use an Integrated Pest Management Strategy to control de Leafcutting ants (Atta cephalotes and related species). First the measurement of the nest is essential to determine the most appropriate type of control to perform and calculate the amount of product needed.The manual control is used only for small nests within the first three months, between the bridal flight and the opening of the first orifice. The manual destruction of the nest and the queen is done by using a shovel or pin, since the chamber is only 20-30 cm deep. Chemical control with powdered formicides for small and medium-sized nests through the use of the insufflator so that the product penetrates into the chambers. Do not apply the dust on the roads because it only controls the ants in transit, but do not eliminate the anthill, besides it contaminates the soil. For large nests, the thermo- fogg Generator are useful using a dose of 50 cm3 of chlorpyrifos per liter of ACPM (Diesel Fuel) at the rate of one minute of thermospray per 10 m2 of nest. Toxic baits, in the form of a pellet based on sulfluramide, avamectin or fipronil. Use 8 to 10 grams per square meter of nest. They should be applied on dry days and with gloves, placed in mounds on the side of the road near the forage mouth so that the workers load them up to the nest. Never apply inside the nest. Likewise, biological control using baits based on entomopathogenic fungi such as Metarrhizium anisopliae and Beauveria bassiana and antagonists such as Trichoderma lignorum contaminate the symbiont fungus Leucoagaricus gongylophorus of the leafcutting ant, causing the death of the colony. For more information on this subject please see: La Hormiga Arriera Atta cephalotes (Hymenoptera:Formicidae) In: Bustillo A.E (Ed.) Pp: 323-329. Los Insectos y su manejo en la Caficultura Colombiana. 2008. Cenicafé. Chinchiná. 488 p.