The Citronella and Savory Essential Oils Effect on Honeybees (Apis mellifera L.) Mortality

Abstract

Recently a trend to use small concentrations of the essential oils of (Cymbopogonschoenanthus) or (Saccocalyxsatureioides) to control pests has extended. They are often used to suppress biotic enemies such as fungus, moulds, bacteria and insects. What is not known is whether these oils also influence beneficial beings such as honeybees. In preliminary experiments foragers’ bees were exposed by inhalation to different concentrations of C. schoenanthus) or (S. satureioides essential oils. Results showed that bees’ mortality in inhalation test increased with increase in concentrations of essential oils and exposure time. Both essential oils showed LC₅₀ greater than 5 µl/ml.Meanwhile 205 µl/ml concentrations were more detrimental. Disturbance of locomotion and contractions of bees recorded by video sequences registered revealed that bees exposed to C. schoenanthus presented lesser contractions and were more active than bees exposed to S. satureioides whom presented more contractions and lesser locomotion activity. Our research provides further evidence supporting the use of conditioning techniques to evaluate the use of essential oils as optimal substances to be considered as alternative controls of pests assuming honey bee safety.