Bees: EFSA tackles multiple stressors

Bees are under attack from many directions. Parasites, infectious agents, agro-chemicals and environmental changes are some of the stressors that are known to damage honeybee colonies. But how do these factors work in combination? And is it possible to devise a model that can take account of all these stressors and predict how they will affect a colony in a given place at a given time?

EFSA has launched a major project to address these questions, with the ultimate goal of establishing a framework for the risk assessment of multiple stressors in honeybee colonies. The multiannual project will involve scientists from a range of relevant fields, such as bee specialists, as well as experts in animal health, plant health, pesticides, data and modelling. EFSA will be working closely with the European Commission, Member States, other EU agencies and research bodies.

Simon More, a veterinarian from University College Dublin who is chairing EFSA’s Multiple Stressors in Bees (MUST-B) working group, said: “We have set ourselves an ambitious but very exciting task. This kind of integrated approach to assessing risks to bees is absolutely necessary if we are to understand how these different stressors combine to kill or weaken honeybee colonies.”

He added: “We basically need two things to build our framework: reliable, harmonised monitoring data – on the presence in hives of infectious agents, such as bacteria and viruses, or pesticide residues, for example – and a computerised simulation model that can process the data and both explain and predict the effects. It sounds straightforward, but this is a huge scientific challenge.”

EFSA’s pesticide experts have already recommended an existing model which they believe could be adapted to the needs of the project. The BEEHAVE model simulates hive population dynamics by considering environmental factors such as weather conditions, availability of food (pollen and nectar), infectious agents such as the Varroa mite and two associated viruses, and other factors that may affect colony development.

Members of EFSA’s Panel on Plant Protection Products and their Residues (PPR) said that the model in its current form is not suitable for use in regulatory risk assessments, but in the future it could be adapted to predict the effects of pesticides and other stressors on honeybee colonies.

They recommend the inclusion in the model of a pesticide module, additional infectious agents such as Nosema and Foulbrood, and an element that can measure interactions between these infectious agents, parasites, climatic conditions and landscape.

On the data side of the MUST-B project, EFSA’s animal health and welfare experts are currently working to develop survey methods and tools that could be used to gather information on the health status of honeybee colonies.

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