Diversity of Fungi Associated withAtta bisphaerica(Hymenoptera: Formicidae): The Activity ofAspergillus ochraceusandBeauveria bassiana

Abstract

The grass-cutting ant Atta bisphaerica is one of the most serious pests in several pastures and crops in Brazil. Fungal diseases are a constant threat to these large societies composed of millions of closely related individuals. We investigated the occurrence of filamentous fungi associated with the ant A. bisphaerica in a pasture area of Viçosa, Minas Gerais State, Brazil. Several fungi species were isolated from forager ants, and two of them, known as entomopathogenic, Beauveria bassiana and Aspergillus ochraceus, were tested against worker ants in the laboratory. The two species were highly virulent, achieving 50 percent worker mortality within 4-5 days. It is the first time A. ochraceus, a commonly found fungal species, is reported to infect Atta species at a high prevalence. Possible uses for the fungus within biological control are discussed.

Purpureocillium lilacinum, potential agent for biological control of the leaf-cutting ant Acromyrmex lundii

“…Previously, only Aspergillus flavus was known to be an occasional pathogen of leaf-cutting ants, particularly of A. echinator (Schmid-Hempel, 1998;, whereas in another study with A. echinator and A. octospinosus ants, none of the foragers or nest workers collected was found to be infected by entomopathogenic fungi . Only for A. bisphaerica it was found an abundance and diversity similar to that reported here (Ribeiro et al, 2012). We found that the diversity of such pathogens varied among colonies, as well as for the same colony from year to year.…”

“…These results are similar to those obtained in other pathogenicity tests at the same concentration with other commonly used entomopathogens against leaf-cutting ants, such as Beauveria bassiana or Metarhizium anisopliae. For example, an LT 50 of 5 days was shown for the same concentration of B. bassiana over Atta sexdens sexdens soldiers, although with a lower effect of these strains (41.7% percentage of infection) (Loureiro and Monteiro, 2005), and an LT 50 of 6 days in Atta bisphaerica workers (Ribeiro et al, 2012). Similar results were obtained for two isolates of M. anisopliae on A. sexdens sexdens, with LT 50 between 3.8 and 6.0 days, but with 45.1% percentage of recuperation (Loureiro and Monteiro, 2005).…”

“…Furthermore, the entomopathogens naturally carried by the ants were responsible for the high mortality found in controls. In addition, most studies use a low number of samples from field colonies or laboratory-maintained colonies (Hughes et al, 2002;López et al, 1999;Mattoso et al, 2011;Poulsen et al, 2006;Ribeiro et al, 2012). However, we purposely used ants brought from several colonies from the field, which resulted in differences in survival among colonies, contrary to what has been previously reported.…”

Diversidad de micobiota en diferentes especies de hormigas cortadoras de hojas y sitios de Argentina

“…Microorganisms within this microbiota include: asexual fungi (Rodrigues et al 2005a,b;Pinto-Tomás et al 2009;Ribeiro et al 2012), yeasts (Carreiro et al 1997;Pagnocca et al 2008) and bacteria (Haeder et al 2009). Functionally, they include symbionts, saprotrophs, entomopathogens and pathogens of Leucoagaricus spp.…”

Effects of entomopathogenic fungi on the mortality and immune system of the leaf‐cutting ant Acromyrmex subterraneus subterraneus

“…The concentration used in this study was chosen based on previous works by Ribeiro et al (2012) and Couceiro et al (2013), which indicate that this concentration is sufficient to obtain satisfactory results without killing ants too fast because of high conidia concentrations (which could interfere with the data analysis). Using a 1 000-ll pipette, 2 ml of these solutions was applied to Petri dishes containing the entomopathogenic fungus with an abundance of conidia.…”