Bioactivity of Essential Oils from Patagonian Wild Plants: Acaricidal and Insecticidal Effects on Varroa destructor...

Varroa destructor represents a major threat to honeybee colonies worldwide, prompting the search for alternative organic acaricides. This study evaluated the biological activity of essential oils extracted from three Patagonian wild plants-Adesmia boronioides, Dysphania multifida, and Senecio filaginoides-on both V. destructor and Apis mellifera. Chemical analysis revealed that A. boronioides oil was dominated by esquelenone (34.49%), D. multifida by ascaridole (34.87%), and S. filaginoides by α-pinene (40.87%). All essential oils exhibited acaricidal activity, with D. multifida showing the lowest LC₅₀ against V. destructor (1.1 µL/mL at 24 h). Toxicity assays on adult bees indicated that A. boronioides and D. multifida significantly reduced bee survival, whereas S. filaginoides did not appear to cause significant mortality (LC₅₀ = 139.5 µL/mL). Repellency tests for A. boronioides and D. multifida showed significant mite repellence. Larval assays revealed a high survival rate under S. filaginoides treatment (survival rate > 80.24%), in contrast to the reduced viability observed with the other oils. The high selectivity index of S. filaginoides underscores its potential as a selective and safe botanical acaricide. Moreover, its LC₅₀ decreased over time, suggesting a residual acaricidal effect. These findings support S. filaginoides as a promising candidate for sustainable V. destructor control.