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.
Highlights
Las abejas son reconocidas por su importancia en los sistemas de producción agrícola debido a su actividad y eficiencia polinizadora (Greenleaf & Kremen, 2006; Klein et al, 2009)
We evaluated five doses for each route and insecticide, in a total of 25 medium-size workers for each dose by duplicate
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
Summary
Cría de colonias de B. atratus: Para el desarrollo del estudio se criaron 101 colonias de B. atratus bajo condiciones de cautiverio en el laboratorio Cría de Abejorros de la Universidad Nueva Granada (N 4°56 ́34.88 ́ ́ - O 74°00 ́38,02 ́ ́), siguiendo el protocolo de cría desarrollado por el laboratorio Biodiversidad y Ecología de Abejas Silvestres - BEAS (Cruz et al, 2007; Pacateque et al, 2012, Riaño et al, 2014). Se evaluaron 25 obreras de tamaño medio procedentes de diferentes colonias, las cuales eran individualizadas en frascos de vidrio con ventilación, CUADRO 1 Descripción de la dosis (/L de agua) y concentración (g i.a/L agua.) de los productos comerciales usados y las concentraciones evaluadas en DL50 por exposición tópica (T) y oral (O) en obreras de B. atratus i.a Dosis Im 1 mL. En el caso de los i.a. Imidacloprid y Thiocyclam hidrogenoxalato, los resultados obtenidos con el cálculo de la DL50 por exposición tópica, muestran que estos son altamente tóxicos para las obreras de B. atratus a partir de los rangos propuestos por USDA (2009) (DL50 < 1 μg i.a./abeja) (Cuadro 2). CUADRO 2 Dosis aguda letal media (DL50) de los i.a. Imidacloprid (Im), Thiocyclam hidrogenoxalato (Th) y Spinosad (Sp) por exposición tópica y oral en obreras de B. atratus i.a. Exposición n Pendiente (± ES)
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