Evaluación de la actividad entomopatógena de diversos aislamientos de hongos y cepas de Bacillus thuringiensis para el potencial desarrollo de un bioformulado contra las hormigas cortadoras de hojas de la especie Atta cephalotes
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Leaf-cutting ants (Atta and Acromyrmex) are one of the most devastating pests in the Neotropical region because of their complex hierarchical organization divided in castes, claustral social life, eusocial behavior to care larvae and protect their symbiont fungus and capacity to forage fresh leaves during the day or night. Considering these factors, and including their hability to recognize and remove potentially harmful particles from their fungus garden, agrochemical control has become a hard task to eradicate this pest. Therefore, the objective of this project was to find out if Bacillus thuringiensis and fungi strains isolated from leaf-cutting ant nests could be applied as bioinfectious agents against Atta cephlotes workers. Ingestion assays adding different Bt lyophilized extracts was a proper method to recognize 3 Bt strains that reached mortality percentages in the interval of 45 and 54%, with subletal concentrations between 9,97×101 and 5,86×107 μg mL-1, as well as subletal times between 5 and 6 days; values that fit with similar reports where δ-endotoxins were used to determine their entomotoxicity on hymenopteran species. Patogenicity and virulence assays adding microfungi enhanced doses allowed to identify 6 strains that exhibited high toxicity, which were morphotypically similar to Metarhizium, Beauveria, Paecilomyces and Aspergillus, common parasites that coexist with leaf-cutting ant colonies according to the consulted literature. Those entomopathogenic strains showed mortalities of 81% - 33%, where the possible Metarhizium strain produced the higher virulence on insects in comparison with the Aspergillus strains, and LD50 y LT50 values were estimated between 4,28×101-1,00×105 spore mL-1 and 5-6 days, respectively.
Proyecto de graduación (Licenciatura en Ingeniería en Biotecnología). Instituto Tecnologíco de Costa Rica. Escuela de Biológía, 2015.