Refuse dumps in Atta cephalotes (Hymenoptera: Myrmicinae) nests as a source of native entomopathogens for biological control

ABSTRACT

Atta cephalotes (Hymenoptera: Myrmicinae) is a dominant species of leafcutter ant in some Latin American countries, and its high abundance and varied defence mechanisms have made it an agricultural and urban pest that is difficult to control. The use of chemical control has an adverse impact on the environment and human health; for that reason, microbiological control is a viable and desirable alternative. From this perspective, we assessed the entomopathogenic capacity of nine fungi isolated from the waste produced by laboratory colonies. For each treatment, 210 workers were distributed in fourteen 15-ant experimental units, each individual being washed in a 10⁸ conidia/mL suspension for ten seconds. A negative control consisting of sterile peptone and two positive controls, commercial strains of Beauveria bassiana and Metarhizium anisopliae sensu lato , were established. In total, 12 treatments were assessed and the response variable was the corrected cumulative mortality over ten days. Data from the five fungi isolates demonstrated entomopathogenic capacity. On the sixth day after exposure, a strain of Aspergillus flavus produced the highest mortality rate (91.5%) while Penicillium commune (85.3%), Aspergillus ochraceus (79.2%) and Fusarium proliferatum (61.7%) showed lower mortality rates. Both native A. flavus and P. commune fungal isolates resulted in higher mortality than the two commercial strains, showing them to be promising control agents for A. cephalotes workers.

KEYWORDS:

• Biological ant control
• symbiotic association
• leaf-cutting ants
• ant waste material

Acknowledgements

The authors would like to thank Colciencias for financial support for this project through the ‘Cuticular bacteria associated with the leaf-cutting ant Atta cephalotes (Hymenoptera: Myrmicinae) in Colombia: Ecological interactions and potential of defence in the colony’, Project CT-004-2017, as well as the Vice-Rectory Office of the Universidad del Valle through the ‘Formulation of a microbial conjugate for the biological control of natural colonies of the leaf-cutting ant Atta cephalotes (Hymenoptera: Myrmicinae)’, Project CI 7926. We would also like to thank the VRI, Universidad del Valle for the English translation service. We thank the members of the Group on Ecology of Agroecosystems and Natural Habitats (GEAHNA), and the Entomology staff of the Universidad del Valle. We are particularly grateful to Diana Ortiz and Jonathan Rodríguez for their support throughout the development of this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Sandra Milena Valencia-Giraldo http://orcid.org/0000-0002-4569-622X

Karen Castaño-Quintana http://orcid.org/0000-0002-6403-8150

Carolina Giraldo-Echeverri http://orcid.org/0000-0003-3028-6436

Inge Armbrecht http://orcid.org/0000-0003-0574-2559

James Montoya-Lerma http://orcid.org/0000-0003-2122-1323

Additional information

Funding

This work was supported by Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS ) [grant number Project Contrato CT-004-2017]; Universidad del Valle [grant number Project CI 7926].