Toxicity of straight-chain fatty acids to leaf-cutting ants Atta sexdens rubropilosa (Hymenoptera: Formicidae) and the symbiotic fungus Leucoagaricus gongylophorus

This work determined toxicity and attractiveness of straight-chain fatty acids (C-5 to C-12) to Atta sexdens ruhropilosa (Forel) workers. The effect to the symbiotic fungus, Leucogaricus gongylophorus (Singer) Moller, was also tested with the fatty acids C-6 to C-12. A strong mortality of leaf-cutting ants that were fed with an artificial diet containing fatty acids C-5 to C-9 at concentrations above 1.0 mg.ml(-1) was observed. Rice flakes impregnated with solutions of these fatty acids were repellent to leaf-cutting ants. Contact experiments showed that treatments with C-6 and C-7 at concentration of 100 mg.ml(-1) significantly reduced the survival rate of leaf-cutting ants. The fatty acids C-8 to C-11 were toxic to leaf-cutting ants when topically tested at concentration of 200 mg.ml(-1). In relation to the fungus' bioassays, the fatty acids C-6 to C-12 at concentration of 0.1 mg.ml(-1) inhibited 100% of the fungal development. Although when the concentration was reduced by half no inhibition effects were observed. The results showed that straight-chain fatty acids have desirable properties for controlling leaf-cutting ants since they directly interfere with both organisms of the symbiotic relationship. The potential of fatty acids as well as ways to control leaf-cutting ants with these compounds are discussed in this article.