Fungos encapsulados em matriz de pectina visando o controle de formigas cortadeiras

Abstract

The main form of control of leaf-cutting ants is through granulated baits based on the active ingredient sulfluramid, but its use is associated with several environmental damages. Biological control with fungi can be a sustainable alternative, but it depends on the development of effective transmission vehicles. Therefore, the objective of this work was to evaluate the development of the fungi Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea, and Trichoderma harzianum encapsulated in a biopolymeric pectin matrix, aiming at the control of leaf-cutting ants and their mutualistic fungus Leucocoprinus gongylophorus on a laboratory scale. For that, the following procedures were carried out: i) evaluation of the topical toxicity of commercial fungi on workers of leaf-cutting ants; ii) evaluation of the growth of commercial fungi on leaf cutting ant workers; iii) production of the encapsulates; iv) evaluation of the growth of fungi encapsulated in culture medium; v) evaluation of the antagonistic activity of encapsulated fungi on the mutualistic fungus; vi) characterization of encapsulated fungi using scanning electron microscopy (SEM); vii) analysis of the acceptance of encapsulated fungi in subcolonies. By the topical test, it was possible to observe the stability in the survival of the workers of the control and the treatment with M. anisopliae during the eight initial hours of evaluation. In the other treatments, mortality already occurred in the first hour. After eight days of evaluation, the treatments T. harzianum, M. anisopliae, and I. fumosorosea caused the highest worker mortality, and B. bassiana the lowest. As for the growth of commercial fungi on the workers, in the treatments with the fungal suspensions, it was observed the germination of the conidia in the cuticle of the ants and horizontal contamination of the mutualistic fungus. After six days of evaluation, the encapsulated fungi plated in the PDA culture medium showed similar growth to the commercially plated fungi. After offering the encapsulated for five consecutive days, low loading values were observed in all treatments and the control. Thus, it can be concluded that the encapsulation process did not interfere with the sporulation and germination of commercial fungi. However, further evaluations are still necessary to make the encapsulated more attractive to leaf-cutting ants.