The consumption of Eupatorium buniifolium essential oil does not affect survival or ethyl oleate production in honeybees.

ROSSINI C.; RODRIGO, F; DAVYT, B; UMPIERREZ, M.L.; GARRIDO P, M.; PORRINI M. P.; EGUARAS M, J.

Nápoles

Congreso; XI European Congress of Entomology; 2018

Sociedad Entomológica Italiana

In the search for alternative control agentsfor Varroa destructor (Mesostigmata: Varroidae), the ectoparasite thatmay contribute to the honeybee colony collapse disorder we have selected the essentialoil from Eupatorium buniifolium(Asteraceae) aerial parts. The vapors from this essential oil showed fumigantactivity against Varroa with notoxicity for bees in laboratory assays as well as moderate activity in apreliminary field trial [1]. These results prompted us to furtherinvestigate on other potential acute toxic and sublethal effects of this EO onbees when applied by different means. The acute toxic activity was studied byestimating the LD50 and LD90 in two tests: a) a CompleteExposure Test [2] and b) a bioassay of topic toxicity followingthe EPA recommendations (OCSPP 850.3020 guide, 2012). In the first case, the LD50was 0.15 mg/cm2 (fiducial interval 0.11-0.18, p< 0.01 PROBIT analysis); and the LD50 according to the EPAprotocol was 252 mg/bee (fiducial interval 207-318, p < 0.01PROBIT analysis) indicating that this product can be considered safe (EPA recommendationfor safe products is a LD⁠50 greater than 25 μg/bee). The chronic effectsby ingestion of this essential oil was also studied following the guidelines inThe Coloss Beebook [3]. In this assay, the essential oil wassupplied in the diet of 2-day old bees for 12 days. During the assay, the foodconsumption was not different among bees fed with the essential oil atdifferent doses (300 to 6000 ppm) and the control bees (ANOVA, p < 0.01); neitherwas the survival among groups (survival analysis Kaplan-Mayer). Besides, at theend of the assay the production of ethyl oleate, a primer pheromone that regulatesthe worker behavioral changes [4] and that has been reported to change understress conditions [5, 6], was quantified by GCMS. Our results showedthat bees that had consumed the essential oil exhibited similar titers of ethyloleate as control bees (ANOVA, GLM, P > 0.05). These results point to the E. buniifolium essential oil as a goodcandidate to develop a botanical acaricide.