Determining the foraging potential of oilseed rape to honey bees using aerial surveys and simulations

Abstract

The modern agricultural landscape is characterised by large areas of monoculture, including fields of mass-flowering crops. These may benefit bees by providing abundant forage, but may cause harm if the fields are treated with insecticides. Here, we investigated the potential exposure of honeybee colonies to pesticides in flowering oilseed rape (OSR) in England using a combination of aerial photographs and geographical modelling. Aerial photographs were used to detect and map fields of blooming OSR in eight 20 Â 20 kilometers 2 areas across England where OSR is grown. We determined the distance to the nearest OSR field for randomly chosen positions (i.e., potential hive locations) using a digital map made of each area. The proportion of colonies within foraging range to the nearest OSR field in each area was then calculated using published data on honeybee foraging distances obtained by waggle dance decoding. We found that the distribution of distances to the nearest OSR field varied greatly among study areas, ranging from almost all colonies being within range to almost all being out of range (6-79% were within median foraging distance). In one study area, we examined changes over a 4-year period and found little year-to-year variation due to crop rotation (23-36% within median foraging distance). Our specific results show that exposure in England to OSR and to any chemicals used in treatment varies greatly among areas. Overall, our methodology provides a novel way of quantifying the exposure of bee colonies or other central place foragers to a particular crop or land-type at a landscape level.Determinació n del potencial de pecoreo de la colza para las abejas melíferas mediante reconocimientos aé reos y simulaciones El paisaje agrícola moderno se caracteriza por extensas áreas de monocultivo, incluyendo campos de cultivos de floració n masiva. Éstos pueden beneficiar a las abejas al proporcionar alimento abundante, pero pueden causar daño si los campos son tratados con insecticidas. Aquí se investigó la posible exposició n de las colonias de abejas de miel a la floració n de la colza (OSR por sus siglas en inglés) en Inglaterra mediante el uso de una combinació n de fotografías aéreas y de modelado geográfico. Se usaron fotografías aéreas para detectar y mapear campos de OSR en ocho áreas de 20 x 20 km a lo largo de Inglaterra donde se cultiva la colza. Se determinó la distancia al campo de OSR más cercano desde posiciones escogidas aleatoriamente (es decir, localizaciones potenciales de colmenas) utilizado un mapa digital hecho para cada área. La proporció n de colonias dentro del rango de pecoreo del campo de colza más cercano se calculó entonces a partir de los datos publicados sobre las distancias de pecoreo de las abejas melíferas, obtenidas mediante la decodificació n de la danza de las abejas. Encontramos que la distribució n de distancias al campo de colza más cercano varió mucho entre las áreas de estudio, oscilando desde casi todas las colonias dentro del rango, a casi todas fuera del rango (6% -79% ...

Gut microbiota composition is associated with environmental landscape in honey bees

“…Mass-flowering crops such as OSR have been shown to enhance pollinator abundance because they provide additional pollen and nectar resources (Holzschuh, Dormann, Tscharntke, & Steffan-Dewenter, 2013;Riedinger, Renner, Rundlöf, Steffan-Dewenter, & Holzschuh, 2014;Schürch, Couvillon, & Ratnieks, 2016;Westphal, Steffan-Dewenter, & Tscharntke, 2003). Therefore, greater abundance of forage and of a specific forage type may drive microbial community composition.…”

Floral resource wastage: Most nectar produced by the mass‐flowering crop oilseed rape (Brassica napus) is uncollected by flower‐visiting insects

“…More broadly, the level of floral resource wastage in MFCs will likely be affected by the spatial distribution of OSR in the landscape. Central‐place foragers, which are ‘tied’ to habitats containing nest sites, will be less likely to be within foraging range of OSR if it is concentrated in large fields with large distances between them (Schürch et al., 2015 ). Alternatively, if the same area of OSR was distributed in more frequent but smaller fields a greater number of insects will be within foraging range.…”

“…Alternatively, if the same area of OSR was distributed in more frequent but smaller fields a greater number of insects will be within foraging range. Models have shown that the proportion of honeybee colonies within foraging range of the nearest OSR field can vary greatly throughout Britain, between 6% and 79% of colonies in a region, due to the spatial distribution of OSR in the landscape (Schürch et al., 2015 ). Indeed, our data indicate that insect abundance was two‐fold greater at the field edge than inside (>100 m), suggesting that smaller fields will increase accessibility for insects and increase the percentage of available floral resources gathered (Woodcock et al., 2016 ).…”

Beekeeping, stewardship and multispecies care in rural contexts

“…With careful management, colonies can benefit from being placed near, or amidst, OSR. In contrast, this crop often holds risks for other species due to the high level of neonicotinoids and other agrochemicals associated with its cultivation (Schürch et al., 2015; Woodcock et al., 2017). It has also been critiqued due to the tendency for its monocrop cultivation, creating a ‘boom and bust’ forage source that can be difficult for honey bees if not managed carefully: ‘ If you go to a hive and the oilseed rape flow has stopped, for a few days afterwards they are not in good humour!’ (MIB60).…”