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

Abstract

Varroa destructor represents a major threat to honeybee colonies worldwide, prompting thesearch for alternative organic acaricides. This study evaluated the biological activity ofessential oils extracted from three Patagonian wild plants—Adesmia boronioides, Dysphaniamultifida, and Senecio filaginoides—on both V. destructor and Apis mellifera. Chemical analysisrevealed that A. boronioides oil was dominated by esquelenone (34.49%), D. multifida byascaridole (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/mLat 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 significantmortality (LC50 = 139.5 µL/mL). Repellency tests for A. boronioides and D. multifida showedsignificant mite repellence. Larval assays revealed a high survival rate under S. filaginoidestreatment (survival rate > 80.24%), in contrast to the reduced viability observed with theother oils. The high selectivity index of S. filaginoides underscores its potential as a selectiveand safe botanical acaricide. Moreover, its LC50 decreased over time, suggesting a residual acaricidal effect. These findings support S. filaginoides as a promising candidate forsustainable V. destructor control.