The Eucalyptus snout beetle in Colombia: Selection and evaluation of entomopathogenic fungi as bioinsecticides against Gonipterus platensis

Abstract

The Eucalyptus snout beetles, which belong to the Gonipterus scutellatus species complex, cause heavy damage to Eucalyptus spp. worldwide. The species was reported in Antioquia, Colombia for the first time in 2016, threatening more than 115,000 ha of planted Eucalyptus spp. Elsewhere, its damage has been controlled using Anaphes spp. as classical biological control, but Anaphes spp. are not available in Colombia, where there are no documented control methods for this species to date. We identified the Gonipterus species using molecular methods and isolated entomopathogenic fungi from naturally infected beetles collected from the current distribution area in Colombia. We characterised the fungal isolates, selecting the best to develop a biological control agent. We considered insecticidal activity, UV-B radiation tolerance, yield, germination, and enzyme activity of conidia in making our selection. We confirmed the presence of G. platensis in Colombia, with adults naturally infected by Beauveria spp. and Metarhizium spp. From the isolated native fungi, M. brunneum (CA-3), M. robertsii (RI-1), B. bassiana (CA-1) and (CA-2), B. pseudobassiana (SP-1) were identified. We found remarkable differences in response to different variables between the selected isolates and SP-1 and CA-3 were the most virulent. The SP-1 isolate stood out from the rest for being the most tolerant to UV-B radiation, alkaline media, and low temperatures, germinating faster and producing elevated levels of lipases, chitinases, and proteases. The identified promising native fungus isolate, naturally occurring on field individuals, could be used to develop a biopesticide for controlling G. platensis in Eucalyptus spp. plantations in Colombia.