Acromyrmex octospinosus (Hymenoptera: Formicidae) Management: Effects of TRAMILs Fungicidal Plant Extracts

Leaf-cutting ants, Acromyrmex octospinosus (Reich), are considering among the most important pest species of the New World. Until now, the main insecticides used for controlling these ants were synthetic chemicals. Leaf-cutting ants live in obligate symbiosis with a basidiomycete fungus, Leucocoprinus gongylophorus (Heim) Moeller. The crucial role of this symbiotic partner in the nest of leaf-cutting ants has prompted us to focus on A. octospinosus management through the use of fungicides in our study. Five parts of plants identified for their antifungal potential through TRAMIL ethnopharmacological surveys were tested: 1) bulbs of Allium cepa L.; 2) seed pods of Allium sativum L.; 3) green fruits of Lycopersicon esculentum L.; 4) leaves of Manihot esculenta Crantz; and 5) leaves of Senna alata (L.) Roxburgh. One plant extract with strong fungicidal activity (S. alata) against L. gongylophorus was found. The other extracts had lesser fungistatic or fungicidal effects depending on the concentrations used. The data presented in this study showed that TRAMILs fungicidal plant extracts have potential to control the symbiotic fungus of leaf cutting ants, in particular a foliage extract of S. alata.