Currie, C.R. and A.E. Stuart. 2001. Weeding and grooming of pathogens in agriculture by ants. Proceedings of the Royal Society of London, Series B 268: 1033-139.
How do the smallest farmers keep their gardens free of weeds? Farming ants grow their own fungus on leaf pieces they collect as their main source of food, but how do they keep their crops free of the ever-encroaching microbes and fungal parasites?
To answer this question, the authors of this study collected 15 intact colonies of the fungus-growing ant Acromyrmex columbica. They sprayed five with the pathogenic fungi Escovopsis, five with Trichoderma viride (an aggressive fungal parasite that can quickly overgrow the fungus farmed by the ants), and the last five served as controls and were sprayed with water. The colonies were videotaped so the responses of the ants to the parasitic fungi could be analyzed.
The authors found that the ants increased their fungus grooming and weeding behaviors after their colonies had been sprayed with the pathogenic fungi, especially with Escovopsis. To fungus groom, the ants would search the garden using their antennae, stop when they located foreign fungus, then used their maxillae and labium to lift the parasitic fungus off the substrate and pull it through their mouthparts. The ants would weed the top part of the garden where the leaf pieces received the most parasitic fungus after spraying. Weeding involved several ants working together to first chew loose the badly infected leaf piece, then pull it free from the garden matrix and carry it to the dump.
Thus, these little farmers keep their gardens in good condition through careful grooming and weeding.
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