Entomopathogenic fungi isolates to control the borer of yerba mate (Hedypathes betulinus) Kluger (Coleoptera; Cerambycidae)

Abstract

Yerba mate is an important crop of southern Brazil, Argentina and Paraguay, with socio-economic and environmental importance. Due the lack of native herbals, yerba mate has become a monoculture, and as a consequence, insects have become pests, and the borer, Hedypathes betulinus, one of the most important. In order to improve biological control in the crop, this work aims to select in laboratory the most virulent, of 32 isolates of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. and 18 isolates of Metarhizium anisopliae (Metsch.) Sorok. Initially, isolates virolence was evaluated by immersing the adults borers in a fungal suspension, containing 1×108 conidia mL-1, and after, those caused highest confirmed mortality were selected for the second step, wherein it was evaluated the virulence, vegetative growth and conidia production in culture medium, rice and borer bodies. Three isolates of B. bassiana (UNIOESTE 4, UNIOESTE 52 and UNIOESTE 64) and one of M. anisopliae (IBCB 352) reached confirmed mortality equal or superior to 90%, these isolates were selected for the second step, together with the standard isolated GC 716 (B. bassiana). The isolated IBCB 352 of M. anisopliae, despite being the only of this species to be selected for the second step, promoted the high confirmed mortality and conidiogenesis in adults borer, indicating a high inoculums production i, being nominated for field evaluations.