Molecular Responses of Varroa destructor to Thyme Essential Oil Exposure

Tuğçe Olgun; Metin Erdoğan; Miray Dayıoğlu; Ünal Karik

doi:10.30539/tbzcty13

Authors

Tuğçe Olgun Apicultural Research Center https://orcid.org/0000-0003-2386-1244
Metin Erdoğan The Faculty of Veterinary Medicine. https://orcid.org/0000-0003-0975-1989
Miray Dayıoğlu Apicultural Research Center. https://orcid.org/0000-0001-7825-3698
Ünal Karik Department of Medicinal and Aromatic Plants. https://orcid.org/0000-0001-6707-191X

Keywords:

Chemosensing gene (Varroa PRTF-like gene)‎, Chemoreceptor gene (Ionotropic glutamate receptors – IR25a-like gene)‎, Neurotransmitter gene (GABA-activated RDL receptor)‎, Thyme Essential Oil (Origanum onites L.)‎, Varroa mite (Varroa destructor)‎

Abstract

Varroa mites (Varroa destructor) continue to pose a serious threat to honey bee (Apis mellifera spp.) health, exhibiting significant resistance development to synthetic acaricides. This study investigated the efficacy of thyme (Origanum onites L.) essential oil (TEOV) as botanical alternative, focusing on mite survival across different feeding contexts and the underlying molecular responses. Adult mites were exposed to three TEOV doses (0.1, 1, and 10 ppm), across different feeding contexts (GA;larvae, GB;fat body, and GC;live honey bee). Mortality exhibited dose and time dependency, particularly at 24 h post-exposure to TEOV. The most responsive host tissue was found to be the mites feeding on larvae and fat body tissue. Interestingly, the susceptibility of the mites was found to be influenced by the context of feeding, which suggests that nutrition affects the susceptibility of TEOV. At the molecular level, TEOV elicited delayed but dose-dependent transcriptional responses: pheromone receptor transcription factor-like (PRTF-like) was strongly upregulated at higher doses after 24h, consistent with activation of stress- or detoxification pathways, additionally Ionotropic glutamate receptors (IGRs)- Ionotropic Receptor 25a-like (IR25a-like) exhibited a general, significant elevation in response to TEOV exposure, suggesting an effort to activate an adaptive chemosensory response. In contrast, the expression of GABA-activated RDL (Dieldrine Resistance) receptor (GABA-RDL) was not generally affected at any dose or time of observation. The result reveals that the neurotoxic action of TEOV is not through transcription-regulated pathway via this receptor. No activity of the mite genes was detected in the control group indicating that any gene activity changes are attributable to treatment with thyme. The selectivity ratio (SR) was calculated as 17.0. The materials have shown their mortality rates, gene expression and physiology by two mechanisms: a fast action as neurotoxicants and long-term stress for TEOV. All results demonstrate its potential as a plant-derived acaricide.

Received: xx November 2025

Revised: xx February 2026

Accepted: xx March 2026

Published Online First : xx June 2026‎

Author Biographies

Tuğçe Olgun, Apicultural Research Center

Apicultural Research Center, Aegean Agricultural Research Institute, Izmir, Türkiye

Metin Erdoğan, The Faculty of Veterinary Medicine.

Afyon Kocatepe University, Afyonkarahisar, Türkiye.

Miray Dayıoğlu, Apicultural Research Center.

Miray Dayıoğlu, Aegean Agricultural Research Institute, Izmir, Türkiye

Ünal Karik, Department of Medicinal and Aromatic Plants.

Ünal Karik, Aegean Agricultural Research Institute, Izmir, Türkiye

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