Pathogenicity of commercial entomopathogenic fungal strains on the avocado seed borer (ASB), Heilipus lauri (Coleoptera: Curculionidae) under laboratory conditions

Abstract

The avocado seed borer, (ASB) Heilipus lauri Boheman 1845 (Coleoptera: Curculionidae) is an official quarantine pest limiting avocado production and fruit exports from Colombia to pest-free countries. To provide alternatives to manage ASB, the objective of this study was to determine the potential use of commercial strains of Beauveria bassiana and Metarhizium anisopliae as biological control agents of this pest. Pathogenicity of the strains was evaluated by complete immersion of the insect in a spore solution (direct inoculation) or by insect contact with inoculated fruit (indirect inoculation). The B. bassiana strain caused higher mortality (DF = 3, F = 25.7, P = 0.0002), showing an almost eight-fold increase, 55% and 79% mortality, for both concentrations used, 2.5 × 108 spores/mL or 2.5 × 109 spores/mL, respectively. Additionally, the B. bassiana strain showed shorter median survivorship using direct inoculation (15.8 to 8.7 days), a longer delay in the feeding initiation time (50 h), and a decrease in the fruit intake (Anti-feeding index above 50) after indirect inoculation. To our knowledge, this is the first report about the pathogenicity of a commercial B. bassiana strain against ASB in Colombia.