Morphological and infection responses of Psoroptes ovis var. cuniculi to Metarhizium pingshaense and peppermint-based compounds.

Psoroptic mange represents a significant challenge in livestock production due to economic losses and animal welfare concerns. The present study aimed, for the first time, to evaluate the compatibility of the entomopathogenic fungus Metarhizium pingshaense, Mentha piperita essential oil (EO) and its major constituents (menthol and menthone), as well as their acaricidal potential, individually and in combination, against adult Psoroptes ovis var. cuniculi mites collected from rabbits. Mites were also evaluated using scanning electron microscopy (SEM) 24h and 48h after the treatment. The results indicated that M. piperita EO did not compromise M. pingshaense conidial germination. M. piperita EO, menthol, menthone (at 0.01 mg/mL), and the fungus, individually or combined, exhibited significant acaricidal potential, reducing mite survival. Two days post-treatment, mortality rates ranged from 21.67% to 100%. By day 4, groups treated with the lowest fungal concentrations exhibited mortality rates above 75%, differing significantly from the control (40%). From day 6 onward, mortality rates exceeded 95% in all groups, including the control, highlighting the limitations of in vitro assays and the need for improved experimental models. SEM analysis revealed progressive mycelial development on treated mites with structural cuticular alterations consistent with fungal penetration including formations suggestive of appressoria. These findings reinforce the potential of integrating entomopathogenic fungi with plant-derived bioactive compounds as part of sustainable control strategies for mites of veterinary importance.