Entomopathogenic fungi as guardians of elm trees: A review of dual-action biocontrol agents targeting Scolytus spp. and their associated Ophiostoma species

The elm tree, an integral component of riparian ecosystems worldwide, has experienced significant mortality due to Dutch elm disease (DED). This review highlights that only 20 out of the 127 identified species within the genus Scolytus have been reported as vectors of DED. A critical research gap exists in the use of entomopathogenic fungi (EPFs) for controlling Scolytus species that vector DED. Current research has primarily focused on S. scolytus, S. multistriatus, and S. schevyrewi, identifying fourteen EPF species as effective biocontrol agents. Notably, only five of these EPFs, including Metarhizium anisopliae, Beauveria bassiana, Nomuraea rileyi, Trichoderma harzianum, and T. polysporum, have been proposed as antifungal agents against Ophiostoma ulmi and O. novo-ulmi. Additionally, environmental factors, such as temperature and UV exposure, along with synthetic substances like pesticides and fungicides, can significantly impact the efficacy of EPFs in biocontrol applications. The paucity of information on the dual control of elm bark beetles and associated pathogenic Ophiostoma species is notable. Despite the limited scope of existing studies, they underscore the dual benefits of EPFs as both bio-fungicides and bio-insecticides. This review posits that EPFs present an effective approach to integrated pest management for DED and advocates for a renewed focus on research into this promising strategy, taking into account environmental factors that could enhance their efficacy.