ABSTRACT
ABSTRACT This study evaluated the in vitro toxicity and motor activity changes in African-derived adult honey bees (Apis mellifera L.) exposed to lethal or sublethal doses of the insecticides fipronil and imidacloprid. Mortality of bees was assessed to determine the ingestion and contact lethal dose for 24 h using probit analysis. Motor activities in bees exposed to lethal (LD50) and sublethal doses (1/500th of the lethal dose) of both insecticides were evaluated in a behavioral observation box at 1 and 4 h. Ingestion and contact lethal doses of fipronil were 0.2316 ? 0.0626 and 0.0080 ? 0.0021 μg/bee, respectively. Ingestion and contact lethal doses of imidacloprid were 0.1079 ? 0.0375 and 0.0308 ? 0.0218 μg/bee, respectively. Motor function of bees exposed to lethal doses of fipronil and imidacloprid was impaired; exposure to sublethal doses of fipronil but not imidacloprid impaired motor function. The insecticides evaluated in this study were highly toxic to African-derived A. mellifera and caused impaired motor function in these pollinators.
Subject(s)
Animals , Pyrazoles/toxicity , Bees/drug effects , Neonicotinoids/toxicity , Insecticides/toxicity , Motor Activity/drug effects , Nitro Compounds/toxicity , Bees/physiology , Behavior, Animal/drug effects , Lethal Dose 50ABSTRACT
Resumen:Los efectos de los insecticidas sobre las abejas han cobrado gran atención a nivel mundial, sin embargo, son pocos los estudios sobre el efecto de estos agroquímicos en abejas Neotropicales. Bombus atratus es una especie neotropical, distribuida ampliamente en los Andes y es considerado un polinizador importante de ecosistemas y agroecosistemas altoandinos. Sin embargo, al igual que muchas especies silvestres, se desconoce el efecto de los insecticidas en B. atratus. Teniendo en cuenta lo anterior, el presente trabajo determinó la dosis letal media aguda (DL50) por exposición tópica y oral de las formulaciones comerciales de los insecticidas con los ingredientes activos Imidacloprid, Spinosad y Thiocyclam hidrogenoxalato, ampliamente utilizados para el control de plagas de cultivos importantes en Colombia. Las pruebas DL50 se realizaron a partir de modificaciones de los lineamientos establecidos por la EPPO y OEDE para estas pruebas en Apis mellifera. Se evaluaron 5 dosis para cada insecticida y exposición. Se evaluaron 25 obreras de tamaño medio en cada dosis por duplicado. La mortalidad se registró a las 24, 48 y 72 horas después del experimento. Los datos fueron analizados con el modelo de regresión Probit. Para el Imidacloprid la DL50 tópica y oral fue de 0.048 µg/abeja y 0.010 µg/abeja respectivamente. Para el Thiocyclam hidrogenoxalato la DL50 tópica y oral fue de 0.244 µg/abeja y de 0.056 µg/abeja respectivamente. Para el Spinosad, la DL50 por exposición oral correspondió a 0.28 µg/abeja. No fue posible establecer la DL50 por exposición tópica. A partir del cálculo del Cociente de Riesgo (HQ) e Índice de Toxicidad Relativa, los tres ingredientes activos son altamente tóxicos. Se analiza y discute el riesgo debido al uso de los productos evaluados a partir de la naturaleza química de los insecticidas.
Abstract:The effect of insecticides on bees has gained great attention, however, there are few studies that explore this issue on Neotropical bees. Bombus atratus is a neotropical species broadly distributed in Colombia and is considered an important pollinator of both Andean ecosystems and agroecosystems. However, as for many wild bees species, the effect of insecticides on B. atratus is unknow. In this study we determined the acute median lethal dose (LD50) of commercial formulations of insecticides Imidacloprid, Spinosad and Thiocyclam hydrogen oxalate, widely used in Colombia to control several pests of important crops. The LD50 was carried out by oral and contact routes, following and modifying the EPPO and OECD guidelines to perform LD50 on A. mellifera. We evaluated five doses for each route and insecticide, in a total of 25 medium-size workers for each dose by duplicate. Mortality was registered at 24, 48 and 72 hours after the experiment; and data were analyzed with the Probit regression model. For Imidacloprid, contacts and oral LD50 were 0.048 µg/bee and 0.010 µg/bee, respectively. For Thiocyclam hydrogen oxalate, topical and oral LD50 were 0.244 µg/bee and 0.056 µg/bee, respectively. For Spinosad, the oral LD50 corresponded to 0.28 µg/bee; it was not possible to establish the LD50 for the contact route. The Hazard Quotient (HQ) and Index of Relative Toxicity indicated that all three active ingredients are highly toxic. We discussed the risk of the insecticides use on B. atratus, considering their chemical nature. Rev. Biol. Trop. 64 (4): 1737-1745. Epub 2016 December 01.