Laurel leaf extracts for honeybee pest and disease management: antimicrobial, microsporicidal, and acaricidal activity

Abstract

A diverse set of parasites and pathogens affects productivity and survival of Apis mellifera honeybees. In beekeeping, traditional control by antibiotics and molecules of synthesis has caused problems with contamination and resistant pathogens. In this research, different Laurus nobilis extracts are tested against the main honeybee pests through an integrated point of view. In vivo effects on bee survival are also evaluated. The ethanol extract showed minimal inhibitory concentration (MIC) values of 208 to 416 μg/mL, having the best antimicrobial effect on Paenibacillus larvae among all substances tested. Similarly, this leaf extract showed a significant antiparasitic activity on Varroa destructor, killing 50 % of mites 24 h after a 30-s exposure, and on Nosema ceranae, inhibiting the spore development in the midgut of adult bees ingesting 1 × 10(4) μg/mL of extract solution. Both ethanol extract and volatile extracts (essential oil, hydrolate, and its main component) did not cause lethal effects on adult honeybees. Thus, the absence of topical and oral toxicity of the ethanol extract on bees and the strong antimicrobial, microsporicidal, and miticidal effects registered in this study place this laurel extract as a promising integrated treatment of bee diseases and stimulates the search for other bioactive phytochemicals from plants.

Honeybee health in South America

“…The development of new acaricides from plants (propolis, essential oils, organic acids) is a key factor to revert this situation. In this sense, some recent studies report promising molecules for Varroa control (Damiani et al 2010(Damiani et al , 2014Maggi et al 2015 among others).…”

“…In Uruguay, the use of ethanolic extract of propolis on colonies has been a useful prevention strategy (Antúnez et al 2008). Currently, alternative strategies for the prevention and treatment of AFB are being studied, mainly based on essential oils (Fuselli et al 2010;Sabate et al 2012;Santos 844 et al 2012;Damiani et al 2014;González et al 2015;Piana et al 2015), probiotics (Audisio et al 2011), and propolis (Bastos et al 2008). …”

Antimicrobial activity of plant extracts against the honeybee pathogens,Paenibacillus larvaeandAscosphaera apisand their topical toxicity toApis melliferaadults

“…) and Laurus nobilis (Damiani et al . ) showed inhibitory activity against P. larvae with MIC values of 7·51–16·90 mg ml −1 , 2–4 μ g ml −1 , 2–8 μ g ml −1 , 50 mg ml −1 and 208–416 μ g ml −1 respectively. In addition, propolis (plant resins collected by bees) has shown efficacy in inhibiting American Foulbrood (Antunez et al .…”

“…Natural compounds have been evaluated to control diseases in honeybees. Several plant extracts showed antibacterial activity against P. larvae (Flesar et al 2010;Boligon et al 2013;Reyes et al 2013;Damiani et al 2014). Also, essential oils (Albo et al 2003;Fuselli et al 2006;Gende et al 2008) and propolis (Antunez et al 2008) have been tested to control P. larvae.…”

Plant Essential Oils Used Against Some Bee Diseases

“…There are many in vitro research on the fungistatic effect of essential oils obtained from many plants including Coriandrum sativum, Tagetes minuta, Lavandula x intermedia, Laurus nobilis (Damiani et al, 2014;Eguaras et al, 2005;Larrán et al, 2001), Cinnamomum glandulifera, Ocimum basilicum, Rosmurinus offacinalis, Eucalyptus globulus (Larrán et al, 2001), Eugenia caryophyllum, Piper betel, Illicium verum, Cinnamomum cassia, Acorus calamus (Chantawannakul et al, 2003;El-enain et al, 2009;Jatisatienr and Jatisatienr, 1999), Thymus vulgaris, Satureja montana, Origanum vulgare (Colin et al, 1989;Kloucek et al, 2012), Eucalyptus citrodora, Leptospermum petersonii, Leptospermum scoparium (Davis & Ward, 2003), Punica granatum, Psidium guajava, Callistemon viminalis, Cinnamomum zeylanicum (El Shafai, 2012, Litsea cubeba, Croton bonplandianus, Mentha spicata, Matricaria chamomilla, Piper betle, Daucus carota, Cuminum cyminum, Syzygium aromaticum , Juglans regia L. (Garbaczewska et al, 2014;Wianowska et al, 2016), Armoracia rusticana, Cymbopogon flexosus, Allium sativum, Origanum compactum, Thymus satureoides, Cinnamomum aromaticum (Kloucek et al, 2012), Origanum onites (Korukluoglu et al, 2009) Melissa officinalis, Cymbopogon spp. (Gochnauer et al, 1979), Litsea cubeba, Pelargonium graveolens (Nardoni et al, 2017), Propolis (Cinnamic acid, pinocembrin) (Voigt and Rademacher, 2015).…”