Carvone and citral, two promising compounds for controlling the honey bee ectoparasitic mite, Varroa destructor

Abstract

Varroa destructor (Acari: Varroidae) is an external parasitic mite that has compromised honey bee (Hymenoptera: Apidae) health worldwide. Varroa mite resistance to commercial formulations of synthetic acaricides has led to an increasing need for new compounds to control mite infestations in honey bee colonies. Thus, essential oils and plant extracts have been used by organic producers concerned about the environment because they are low‐risk pesticides. This study tested the toxicity of four natural compounds: carvone, citral, cineole and limonene to mites and bees under laboratory conditions. Tau‐fluvalinate was used as positive control. Seven concentrations with logarithmic interval were used to test each compound. The safety margin of the compounds for the bees was calculated from selectivity ratios. Carvone was significantly more toxic to varroa mites (LC50 = 272.74 μg/ml) than the other three compounds but did not differ with tau‐fluvalinate (LC50 = 272.30 μg/ml). Citral was the second most toxic compound to mites (LC50 = 318.54 μg/ml), followed by cineole (LC50 = 3897.65 μg/ml) and limonene (LC50 = 3003.94 μg/ml). Citral and carvone showed low toxicity to worker bees at both 24 and 48 hpt. The LD50 values for citral, carvone and tau‐fluvalinate were 78,459, 106,620 and 143.02 μg/ml at 24 hpt, respectively, which were significantly different from each other. The relative selectivity ratios calculated for carvone, citral and tau‐fluvalinate were 390.9, 246.3 and 0.53, respectively. This study provides preliminary laboratory evidence for the effectiveness and safety of two plant compounds, carvone and citral, that could potentially be used for the control of V. destructor infestations in honey bee colonies.

Inmunotoxicidad comparativa de abejas, Apis mellifera (Hymenoptera: Apidae), expuestas a xenobióticos naturales y sintéticos

“…Considerando que, en general, los productos naturales son considerados selectivos, este hallazgo es significativo. Los compuestos naturales son evaluados principalmente por su toxicidad aguda para los insectos benéficos (Sabahi et al, 2022;Cappa et al, 2022).…”

Imunotoxicidade comparativa de abelhas, Apis mellifera (Hymenoptera: Apidae), expostas a xenobióticos naturais e sintéticos

“…Considerando que, em geral, os produtos naturais são considerados seletivos, esse achado é significativo. Os compostos naturais são principalmente avaliados por sua toxicidade aguda para insetos benéficos (Sabahi et al, 2022;Cappa et al, 2022). No entanto, há informações limitadas sobre como esses compostos afetam as abelhas em nível celular, o que tem graves implicações para sua fisiologia e saúde.…”

First Report on the Synergistic Interaction between Essential Oils against the Pinewood Nematode Bursaphelenchus xylophilus

“…Concerning the air environmental compartment, ecotoxicological information was found for pollinator insects, for example, the honeybee (Apis mellifera). While emamectin benzoate has a reported LD 50 of 0.036 µg/bee, the monoterpenes carvone or citral have extremely higher values, 106,620 µg/bee and 78,459 µg/bee, respectively, which even makes them potential biopesticides able to control Varroa destructor, a highly damaging ectoparasite of honeybees [16,33]. Ultimately, the identified EO mixtures can offer a safer alternative to conventional nematicides while showing improved nematicidal activity against PWNs.…”