SELECTION OF BEAUVERIA BASSIANA, METARHIZIUM ANISOPLIAE AND PAECILOMYCES FARINOSUS ISOLATES, PATHOGENIC TO WORKERS OF ATTA SEXDENS SEXDENS (LINNAEUS, 1758) (HYMENOPTERA: FORMICIDAE)

ABSTRACT

This study was carried out under laboratory conditions, aiming at the evaluation of the efficiency of enthomopathogenic fungi to control Atta sexdens sexdens. We utilized isolates of Beauveria bassiana (AM 9, JAB 06), Metarhizium anisopliae (E 9, AL), and Paecilomyces farinosus (CG 189, CG 195), inoculated on workers. After the collection, samples of workers were separated in groups of eight insects and baths with conidial suspension of 1.0 x 10⁶, 1.0 x 10⁷, 1.0 x 10⁸ and 1,0 x 10⁹ conidia/mL. Each group of ants was transferred to a moist chamber and maintained under starvation at 27 ± 1° C. The tree fungi were pathogenic, although P. farinosus (isolates CG 189 and CG 195) was the most virulent. This isolates were those ones that showed larger percentage of confirmed mortality. The most efficient concentration used in this study was 10⁹ conidia/ mL, with LT₅₀ of 1.48 days for isolate CG 189. Observing the mortality parameter on the third day after evaluation, the concentrations tested afforded the highest mortality (67.6%) and confirmed mortality of 96.05%. The isolates AM 9, E 9 and CG 189 promoted the highest mean mortalities for workers in the shortest time.

KEY WORDS:
Leaf-cutting ant; biological control; microbiol control; entomopathogenic fungi