Oral toxicity of essential oils and organic acids fed to honey bees (Apis mellifera)

Abstract

SummaryNatural plant products have been studied for potential use as in-hive fumigants for suppression of parasitic mites and other pests. A more direct application through direct feeding of bees would avoid problems with fumigant volatility in cold climates and provide a more systemic route of exposure for the target pest. However, there must be a balance between toxicity to hive pests and toxicity (safety) to the bees. We focused on adult bee toxicity when testing ten products: cineole, clove oil, formic acid, marjoram oil, menthol, oregano oil, oxalic acid, sage oil, thymol, and wintergreen. Each product was tested at several concentrations in a sugar syrup fed to bees over several days, and dead bees were counted daily. Oxalic acid was the most toxic of the products tested. Menthol and cineole had mortality levels no different from controls fed plain syrup after 8 days of treatment. At 14 days of treatment, wintergreen was the least toxic, but neither menthol nor cineole were a part of the testing that went to 14 days. Our results indicate that the tested products could all be used safely for treating bees orally if dose is carefully managed in the hive.Toxicidad oral de aceites esenciales y ácidos orgánicos en la alimentación de la abeja de la miel (Apis mellifera) Los productos naturales de plantas han sido estudiados para su uso potencial como agentes fumigantes de represión de ácaros parásitos y otras plagas. Una aplicación más directa a través de la alimentación de las abejas evitaría problemas como la volatilidad de los fumigantes en climas fríos y proporcionaría una vía más sistémica de exposición para las plagas. Sin embargo, debe haber un equilibrio entre la toxicidad para las plagas y la toxicidad (seguridad) para las abejas. Nosotros nos hemos centrado en la toxicidad sobre abejas adultas de diez productos: eucaliptol, aceite de clavo, ácido fórmico, aceite de mejorana, mentol, aceite de orégano, ácido oxálico, aceite de salvia, timol y aceite esencial de wintergreen (salicilato de metilo). Cada producto fue probado con diferentes concentraciones en un jarabe de glucosa que alimentó a las abejas durante varios días, las abejas muertas fueron contadas diariamente. El ácido oxálico fue el producto más tóxico de todos los analizados. El mentol y el eucaliptol presentaron niveles de mortalidad similares a los controles, que fueron alimentados únicamente con jarabe después de 8 días de tratamiento. Tras 14 días de tratamiento, el aceite esencial wintergreen fue el menos tóxico, pero ni el mentol ni el eucaliptol se incluyeron en el análisis a los 14 días. Nuestros resultados indican que todos los productos testados pueden ser utilizados con seguridad por vía oral para el tratamiento de las abejas si la dosis es administrada cuidadosamente en la colmena.

Bumble bee parasite strains vary in resistance to phytochemicals

“…Phytochemicals such as thymol and eugenol, which display strong antimicrobial activity but are relatively benign to bees70, could have high medicinal value for both wild and managed bees that have access to plants containing these compounds. In general, bees are less susceptible than are microbes to toxic effects of essential oils70, and can be attracted to relevant antimicrobial concentrations71, which would increase the likelihood of voluntarily ingesting medicinally significant amounts of these phytochemicals under natural conditions.…”

American Foulbrood in honeybees and its causative agent, Paenibacillus larvae

“…But the efficacy of such a treatment and the absence of adverse side effects on bee vitality (Ebert et al, 2007;Higes et al, 1997) and honey quality still need to be evaluated in practice.…”

Plant essential oils as potential control agents of varroatosis

“…Prospecting criteria may incorporate the investigation of EOs found to be active against other mites of veterinary importance as recently reviewed in (Flamini Phytochem Rev (2011) 10:227-244 239 2006; George et al 2008), such as the poultry red mite, Dermanyssus gallinae GhrabiGammar et al 2009), the ear mite Psoroptes cuniculi (Lans et al 2008), the sheep tick Ixodes ricinus (Garboui et al 2009), the cattle tick, Rhipicephalus (Boophilus) microplus (Jonsson and Piper 2007), etc. Besides, other promissory products to be tested against varroa are the ones that have already being described in other non-varroa related studies as innocuous against bees, such as the Lamiaceae, Hyptis suaveolens (Abramson et al 2007), Ocimum basilicum (Albo et al 2003) and Salvia sclarea (Ebert et al 2007). As a final comment, it is worth of notice that there have been some studies on varroa using volatile chemicals from bees (kairomones) to find the brood cells more suitable (Nazzi et al 2003;Dillier et al 2006).…”