Selection of Metarhizium anisopliae and Beauveria bassiana isolates pathogenic to Atta bisphaerica and Atta sexdens rubropilosa soldiers under laboratory conditions/ Selecao de isolados de Metarhizium anisopliae e Beauveria bassiana patogenicos a soldados de Atta bisphaerica e Atta sexdens rubropilosa em condicoes de laboratorio

• Published in: Ciência rural 2010-06, Vol.40 (6), p.1243
• Main Authors: Castilho, Alzimiro Marcelo Conteiro, Fraga, Marcelo Elias, Aguiar-Menezes, Elen de Lima, Rosa, Carlos Alberto da Rocha
• Format: Article
• Language: Spanish
• Subjects: Biological control; Fungi; Health aspects; Military personnel; Pests
• ISSN: 0103-8478

The ants of the genus Atta are important pests of several crops, pastures and planted forests. The entomopathogenic fungi are among the natural mortality factors of these ants and because of that they have potential to be use in biological control of this pest. The present research aimed to select isolates of Metarhizium anisopliae and Beauveria bassiana pathogenic to soldiers of Atta sexdens rubropilosa and Atta bisphaerica under laboratory conditions. To evaluate the pathogenicity, eight isolates of M. anisopliae and six of B. bassiana were used. The experiment was carried out in a completely randomized design, being the plots composed by a group of ten soldiers per each ant species, and three replicates per treatment. For each isolate, three groups of soldiers were sprayed with conidial suspensions containing 1.0 x [10.sup.8] conidia [ml.sup.-1], kept in moist chamber (25±1°C, 80±1% of RH in the dark) without food, and the mortality was evaluated every day. From the 14 isolates tested, four of M. anisopliae and four of B. bassiana were pathogenic to soldiers of the both ant species. The virulence was evaluated to the isolates that caused mortality equal or higher than 50%. For each isolate, suspensions containing 1.0 x [10.sup.6] to 1.0 x [10.sup.11] conidia [ml.sup.-1] were sprayed on three groups of ten soldiers, and equally kept as on the pathogenicity test. The mortality percentage was calculated each 24 hours for determining TL5a The isolate ENA04 of M. anisopliae was the most pathogenic, causing more than 80% of mortality in the first three days after inoculation, showed higher capacity of spore production on ant cadavers, and was the most virulent to the soldiers of A. bisphaerica, with a [TL.sub.50] of 1.15 days. All pathogenic isolates of A. sexdens rubropilosa soldiers were equally virulent. Key words: leaf-cutting ants, entomopathogenic fungi, pathogenicity, virulence. As formigas do genero Atta sao pragas importantes de diversas culturas agricolas, pastagens e reflorestamentos. Os fungos entomopatogenicos estao entre os fatores naturais de mortalidade dessas formigas e por isso apresentam potencial para serem usados no controle biologico dessa praga. O presente trabalho teve como objetivo selecionar isolados de Metarhizium anisopliae e Beauveria bassiana patogenicos a soldados de Atta bisphaerica e Atta sexdens rubropilosa em condicoes de laboratorio. Para a avaliacao da patogenicidade, foram utilizados oito isolados de M. anisopliae e seis