Carrying and Effect of Granulated Baits Formulated with Entomopathogenic Fungi among Atta sexdens rubropilosa Colonies (Hymenoptera: Formicidae)

Abstract

The present study aimed to evaluate the carrying and effect of (dry) granulated baits containing conidia of entomopathogenic fungi among colonies of the leaf-cutting ant Atta sexdens rubropilosa in the laboratory. This bait type was chosen to facilitate its eventual commercial use. Two applications were performed: in the first, baits with 1x108 conidia/g were utilized while in the second employed concentrations 5 to 8.6 times greater. The baits were formulated with a citric pulp base, with 2 isolates of Beauveria bassiana, 1 of Paecilomyces lilacinus and 1 of Isaria fumosorosea. The following controls were utilized: (I) baits with sulfluramid insecticide, (II) without active ingredient, and (III) Acalypha spp. leaf discs. It was verified that the baits containing fungal conidia were rapidly carried to the nest interior in both applications and were rejected minimally. Thus, the (dry) granulated bait formulation appears to be an adequate vehicle for entomopathogenic fungi. At the doses and concentrations utilized, the fungi provoked only limited worker mortality, not killing the colonies. Given the rapid carrying and low rejection, a higher conidial dose per colony can, perhaps, kill them. Thus, it is inferred that all the isolates tested present potential as an agent to control colonies of leaf-cutting ants.