Commercial Product Based on Metarhizium Anisopliae Affects Survival, Midgut Morphology, and Behavior in the Stingless Bee Scaptotrigona depilis (Hymenoptera: Apidae)

Brazilian social stingless bees are important pollinators and producers of honey, wax, royal jelly, propolis, and other products. These species are experiencing a population decline, attributed to different factors, such as the excessive use of pesticides. Biological control has been proposed as an alternative to chemical control, relying on the use of natural enemies to manage pests, including microorganisms such as entomopathogenic fungi. However, little is known about the effects of these agents on stingless bees. Therefore, this research evaluated the effect of the commercial bioproduct Metarhizium Oligos WP on the stingless bee Scaptotrigona depilis. After 5 and 10 days of exposure, the bees were cold-immobilized and then dissected in saline solution, and the midgut was collected for histological and ultrastructural analyses. Injured organs were analyzed semiquantitatively. Additionally, superoxide dismutase (SOD) and catalase (CAT) activities were determined to investigate the occurrence of oxidative stress. Behavioral assessments were also performed. Although there were no significant changes in SOD and CAT activities, oxidative stress may have been induced, possibly due to the accumulation of reactive oxygen species and free radicals generated during fungal infection. These effects are believed to be the cause of the observed alterations in midgut morphology, as well as physiological and behavioral changes, such as impaired locomotion. The findings demonstrate the negative impact of the bioproduct on S. depilis stingless bees and suggest it may affect their pollination potential.