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Drone surrounded by worker bees. © INRA, MORISON Nicolas

Scientists flying to the rescue of bees

Putting bee ecology back in the debate

A bee forages from flower to flower, visiting grasslands, gardens, forests and fields in turn: that is an image which no longer really corresponds to reality. Most bees have to manage in threatening environments that are arid in the summer, contain inconsistent sources of food and where they are prey to pesticides. Replacing bee ecology at the centre of the debate is the objective of INRA researchers who are trying to establish a link between the excess mortality of colonies and the environments where they live, and notably intensive farming systems.

Agriculture causes major modifications to the bees' environment, in both spatial and temporal terms. In space, because a crop of wheat is not a species that is visited by bees and therefore does not permit the development of colonies, unlike a field of rapeseed which is visited by pollinators. In time, too, because this field of rapeseed, apparently so beneficial to the bees, has a flowering period of less than a month, after which the bees have problems finding anything to eat. It is the impact of these unbalanced environments that the researchers are trying to characterise, to enable the development of alternatives that will be more favourable to pollinating insects.

Updated on 03/27/2017
Published on 05/01/2014

Ecobee: a 45,000-hectare laboratory to study bees

Ecobee is a tool that is unique in the world for the study of bees in their environment. Since 2007, a hundred or so bee colonies have been studied in the heart of the Plaine-Val de Sèvre workshop site, which is managed by the Chizé Centre for Biological Studies (CNRS) and comprises 45,000 hectares made up of 19,000 plots on which the scientists have gathered a mine of information: the crops grown, land use, agricultural techniques, pesticide use, etc.

Throughout the summer months, the colonies are examined every 15 days. In Le Magneraud, INRA scientists measure the weights of honey reserves and harvests, count the numbers of adult bees, the size of broods, mortality rates in front of the hive and hive temperatures, while at the same time screening for any parasites or infections which affect the bees. An analysis is also made of the pollen foraged by the bees, thus providing information on their preferences and foraging routes. Never have bee colonies been studied as closely for such a long period.

As a focus for encounters between researchers and experts from all sides, Ecobee has also enabled the structuring of several major scientific programmes such as Polinov or Ecophyto-Dephy Abeilles.

The seasonal famine that affects bees

Over a year, changes to hive weight should follow a bell-shaped curve. The minima occur at the end of winter, while in the summer the colony will reach its maximum weight at the time of its peak population.  Reserves are therefore assured for the winter. However, in the cereal plains of the Poitou-Charentes region, that is not what is observed. Although the hives do indeed start to gain weight at the end of winter, they surprising lose it in May and June, before a further rise in midsummer. This downturn at the end of spring is a concern to scientists. It may correspond to a period of famine for the honey bees. Major arable crops such as maize and sunflower are not yet in flower, and weeds are becoming more scarce because of the application of herbicides.

A foraging bee on a tansy flower; the blue pellets are due to the colour of this flower's pollen © MORISON Nicolas

CSI Pollen: a survey on the bees' larder

No one doubts that the decline of plant biodiversity is one of the causes of the decline of honey bees. But measuring their degree throughout Europe is a major challenge. This is nevertheless the aim of a major collaboration between researchers and beekeepers in 15 countries, called CSI-pollen (Citizen Scientist Investigation-Pollen). Volunteer beekeepers - sixty of them in France alone - will be given the mission of observing the colour of the pollen pellets returned to their hives. These colours are specific to each type of flower that has been visited; if the pellets are of different colours, which may range from dark red to pale yellow, then the bees have access to a wide variety of flowers. However, a uniform colour indicates a diet that is equally so. In order to study these phenomena in more detail, some beekeepers will send pollen samples to the scientists so that they can evaluate their diversity. Is there a correlation between a poor diversity of harvested pollen and greater mortality or specific diseases? This is a research line that our experts have decided to follow to the end.

Balls of yellow pollen on combs of a bee on a hive © MORISON Nicolas

A unique collection of bee-friendly plants

A research tool as much as a reference site for beekeepers and naturalists, APIBOTANICA is the botanical database held by the INRA Entomology Experimental Unit in Magneraud that contains a unique collection of melliferous plants and their pollens. It represents 450 species that may be foraged by domestic honey bees in Poitou-Charentes, the majority of those they may find on all French farmland. Thus, thanks to their flowering dates, the colours of the pollen pellets harvested by the bees, or the specific shapes of pollen grains, beekeepers can know which flowers their bees have visited.

Where do wild bees nest?

The natural spaces that remain between arable crops (field borders, grasslands, hedges and forest margins) harbour numerous bee species. Thus a landscape of cereal crops may be home to a quarter of the species known in France in an area as small as 0.1% of the territory. Preservation of these remaining natural environments is therefore essential to maintaining this diversity. Programmes designed to improve the quality of landscapes for bees are currently ongoing.