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Les méthodes permettant l’évaluation de la toxicité des pesticides pour les abeilles ont tendance à évoluer ces dernières années et ne se cantonnent plus seulement à la détermination de la DL50 (dose provoquant la mort de la moitié des individus). Les récentes recommandations de l’European Food Safety Authority (EFSA) préconisent notamment de développer des tests à même d’identifier des effets comportementaux dans une gamme d’exposition sublétale. Le présent document décrit une méthode qui permet de mesurer les effets délétères des insecticides sur les capacités locomotrices à des niveaux d’exposition qui ne provoquent pas la mort de l’abeille mais qui peuvent compromettre ses chances de survie ou ses performances au sein de la colonie. A l’instar du « test de vol de retour à la ruche des butineuses expérimentées », ce test pourrait dans le futur donner lieu à l’élaboration d’une méthode réglementaire d’évaluation des effets sublétaux des insecticides, après validation via un test interlaboratoires. Ce test locomoteur de laboratoire s’inspire des méthodes traditionnellement utilisées sur les rongeurs et à ce titre, il est standardisable, et peut en particulier être transposé sur des abeilles d’âge connu, sur tous les stades adultes. Le test est par exemple ici utilisé avec succès sur des abeilles jeunes, âgée de moins de 24h.

This study was supported partly by research grants from National Science and Technology Support task (2012BAD19B06), the earmarked fund for Beijing Leafy Vegetables Innovation Team of Modern Agro-industry Technology Research System (blvt-13), the earmarked fund for Modern Agro-industry Technology Research System (2013003019) and the earmarked fund from Beijing Academy of Agriculture and Forestry Sciences (QNJJ201610).; The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci MED species, formerly known as biotype ‘Q’, has surpassed the MEAM1 species, formerly known as biotype ‘B’, which is threatening agricultural production all over the country as an increasing number of resistance cases have been reported. This situation highlights the need for alternative pest control measures. In this study, the lethal effects of six neonicotinoid and two anthranilic diamide insecticides including the novel compound cyantraniliprole on B. tabaci MED were examined. The sublethal effects of cyantraniliprole on the physiology and behavior of B. tabaci MED were also assessed. Among eight insecticides tested, cyantraniliprole was the most toxic to B. tabaci MED with a LC50 of 2.05 mg/L. The sublethal effects of cyantraniliprole to adult B. tabaci MED were observed at LC10 (0.22 mg/L) and LC25 (0.63 mg/L) concentrations. At these concentrations, cyantraniliprole prolonged the developmental duration and decreased the survival rate of nymph stages, pseudopupae and adults. The oviposition duration and fecundity of females were also reduced significantly. The hatching rate of eggs laid by females exposed to LC10 and LC25 concentrations was also reduced. Altogether, these results demonstrate that cyantraniliprole could be an alternative insecticide for efficient control of B. tabaci MED populations in China.

En 2012, l’UMT PrADE a publié une étude dans laquelle le vol de retour à la ruche de 650 butineuses marquées d'une micropuce électronique RFID a été enregistré, et dont certaines ont été expérimentalement exposées à une faible dose de thiaméthoxam (la substance active des pesticides Cruiser® et Cruiser OSR®) utilisé en protection des cultures. Cette molécule, même administrée à une faible dose n’entraînant pas d’effet direct sur la survie, provoque la disparition des butineuses. En conditions habituelles de butinage, ce phénomène peut aboutir à un taux de mortalité deux à trois fois supérieur chez les butineuses intoxiquées. Il s’ensuivit des controverses sur l’approche scientifique (réalisme des doses, prédiction des effets sur la colonie par un modèle) et sur l’interprétation des résultats (généricité des effets) qui a motivé la réalisation d’une série de travaux pour tenter de les lever une à une. Cette épopée nous a amené à combler de nombreuses lacunes de connaissances sur la modulation des effets toxiques selon le contexte paysager, climatique ou sanitaire des abeilles. Toujours grâce au dispositif RFID, nous avons confirmé pour la première fois l’impact d’un insecticide néonicotinoïde sur la survie des ouvrières en conditions réelles d’exposition au champ., In 2012, colleagues of UMT PrADE tagged 650 free-ranging honeybees with tiny radio-frequency identification (RFID), microships that were glued to each bee’s thorax. This device allowed the researchers to track the bees as they came and went from their hives after an oral exposure to sublethal dose of the insecticide thiamethoxam (active ingredient of Cruiser® and Cruiser OSR®). Compared to the non-exposed bees, the treated bees were about two to three times more likely to die while away from their nests. This study was related to controversy as regards the scientific methodology (fieldrealistic doses, predictive model for colonial effects) and the generalization of results in real conditions. This controversy was a true motivation for our scientific investigation to address the lack of knowledge on the modulation of insecticide effects according to landscape, weather or sanitary status of bees. Using also the RFID device, we confirmed that field exposure to neonicotinoid accelerated the disappearance of bees.

International audience; The present study was intended to evaluate the responses of enzymes in the honeybee Apis mellifera after exposure to deltamethrin, fipronil, and spinosad and their use as biomarkers. After determination of the median lethal doses (LD50), honeybees were exposed at doses of 5.07 ng/bee and 2.53 ng/bee for deltamethrin, 0.58 ng/bee and 0.29 ng/bee for fipronil, and 4.71 ng/bee and 2.36 ng/bee for spinosad (equivalent to 1/10th [LD50/10] and 1/20th [LD50/20] of the LD50, respectively). The responses of acetylcholinesterase (AChE), carboxylesterases (CaEs-1-3), glutathione-S-transferase (GST), catalase (CAT), and alkaline phosphatase (ALP) were assessed. The results showed that deltamethrin, fipronil, and spinosad modulated these biomarkers differentially. For the enzyme involved in the defense against oxidative stress, fipronil and spinosad induced CAT activity. For the remaining enzymes, 3 response profiles were identified. First, exposure to deltamethrin induced slight effects and modulated only CaE-1 and CaE-2, with opposite effects. Second, spinosad exhibited an induction profile for most of the biomarkers, except AChE. Third, fipronil did not modulate AChE, CaE-2, or GST, increased CAT and CaE-1, and decreased ALP. Thus, this set of honeybee biomarkers appears to be a promising tool to evaluate environmental and honeybee health, and it could generate fingerprints to characterize exposures to pesticides.

International audience; This study describes the development of acetylcholinesterase (AChE), carboxylesterases (CaE1, CaE2, CaE3), glutathion-S-transferase (GST), alkaline phosphatase (ALP) and catalase (CAT) as enzyme biomarkers of exposure to xenobiotics such as thiamethoxam in the honey bee Apis mellifera. Extraction efficiency, stability under freezing and biological variability were studied. The extraction procedure achieved good recovery rates in one extraction step and ranged from 65 percent (AChE) to 97.3 percent (GST). Most of the enzymes were stable at −20 °C, except ALP that displayed a slight but progressive decrease in its activity. Modifications of enzyme activities were considered after exposure to thiamethoxam at the lethal dose 50 percent (LD50, 51.16 ng bee−1) and two sublethal doses, LD50/10 (5.12 ng bee−1) and LD50/20 (2.56 ng bee−1). The biomarker responses revealed that, even at the lowest dose used, exposure to thiamethoxam elicited sublethal effects and modified the activity of CaEs, GST, CAT and ALP. Different patterns of biomarker responses were observed: no response for AChE, an increase for GST and CAT, and differential effects for CaEs isoforms with a decrease in CaE1 and CaE3 and an increase in CaE2. ALP and CaE3 displayed contrasting variations but only at 2.56 ng bee−1. We consider that this profile of biomarker variation could represent a useful fingerprint to characterise exposure to thiamethoxam in the honey bee A. mellifera. This battery of honey bee biomarkers might be a promising option to biomonitor the health of aerial and terrestrial ecosystems and to generate valuable information on the modes of action of pesticides.