Mariano Higes is a bee researcher at the Bee Diseases Laboratory of the Spanish bee research institute, the Centro Apícola de Castilla-La Mancha. Bayer research talked to him about bee health.

Are crop protection products dangerous to bees?
The finger of blame is often pointed at insecticides, but our investigations show that they are not involved at all in bee losses in Spain. This does not mean that in some parts of the country uncontrolled use of these insecticides cannot cause bee losses, but they are not behind widespread bee death.

What other factors are responsible for bee death in addition to varroa?
It varies from region to region. For example, in Spain we have found that Varroa destructor is not the only problem. The single-cell parasite Nosema ceranae, which also originated in Asia, also plays an important part, as do the viruses spread by varroa and nosema.

Will bee numbers recover?
Not without efficient control of the varroa mite by the targeted use of appropriate mite controls, that much is certain. We also need products to control Nosema ceranae.

A four-year field study by the Bee Research Institute in Oberursel, Germany has found that the parasite is at the heart of the problem: "If we keep up our efforts at controlling the varroa mite, many more bee populations will survive," explains Professor Nikolaus Koeniger, who was the institute’s director for many years; he and his wife have been devoted to studying the varroa mite for decades. 

As this famous bee expert couple knows, it is horizontal infection that is most dangerous. "Particularly at the end of the flowering period, foraging bees from healthy colonies invade colonies weakened by varroa to steal honey. They then become infected and take back large numbers of mites to their own population."

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