Exploring the pathogenicity and infection processes of Akanthomyces lecanii against Diaphorina citri for biocontrol applications

The Asian citrus psyllid ( Diaphorina citri ) is a key pest of citrus crops and transmits the bacterium that causes Huanglongbing (HLB). Due to the limitations of chemical pesticides, including resistance development, there is increasing interest in biological control agents, such as entomopathogenic fungi. This study investigates the potential of Akanthomyces lecanii as a biocontrol agent against D. citri . We assessed the pathogenicity of two A. lecanii isolates, V3450 and V09, across different developmental stages of D. citri (eggs, nymphs, and adults) using varying conidial concentrations. Our results demonstrated that isolate V3450 was the most virulent, particularly against nymphs, achieving 100% mortality at a concentration of 1 × 10⁸ conidia/mL. In comparison, isolate V09 showed lower virulence, particularly at lower concentrations. Qualitative light and scanning electron microscopy of isolate V3450 documented conidial adhesion, germination, and cuticle-associated infection structures. External hyphal growth and conidial formation were observed on infected insect surfaces during disease progression and were associated with subsequent host mortality. These findings demonstrate that A. lecanii is a promising microbial control candidate against D. citri and provide a basis for further evaluation under greenhouse and field conditions.