There is some controversy about honey bee deaths, and whether they are linked to a group of pesticides known as neonicotinoids. Neonicotinoid pesticides include:
There is also Fipronil, a systemic pesticide, which works in a very similar way to neonicotinoids.
Neonicotinoids are neurotoxins that act on information processing (and hence ability to function or perform tasks), by affecting a specific neural pathway common in invertebrates. In other words, the nervous system is attacked.
Treated insects may exhibit leg tremors, rapid wing
motion, disoriented movement, paralysis and ultimately death.
These pesticides are systemic in that they permeate the whole plant, being dispersed into plant tissues. This means that insects sucking on the plant will ingest the pesticide and may suffer some of or all of the effects described above.
In other words, neonicotinoids create a toxic plant, thereby killing insects which feed on them.
To an extent, it depends on the country where sold. However:
The table below indicates level of toxicity to bees of various neonicotinoids, in comparison with DDT. You can read more about this DDT.
In Europe, they defend their products with regard to bees, typically stating that they do not pose 'unacceptable risk'. The word 'unacceptable' arguably provides 'wriggle room' for manufacturers.
Nevertheless, their own literature is revealing. To read an example see how do neonicotinoids work.
The term 'CCD' is complex, and not clear cut. It appears to have been used originally to define a set of symptoms, but there are variations of definitions and symptoms described. Read more about CCD.
The term CCD first appeared in 2006, following a dramatic rise in the number of disappearances in honey bee colonies in North America. Literally tens of thousands of bees were disappearing from hives each day, with some beekeepers reporting losses of 50% of their hives.
Yet the phenomenon of honey bee deaths and disappearance in such a dramatic manner certainly began sooner than 2006, in Europe.
There is significant debate about the factors involved, including neonicotinoid pesticides. For example, Varroa mites may or may not be present.
In France, where dramatic honeybee losses were observed, and honey production dropped from 40,000 to 25,000 tons between the years 1995-2001, it was noted that these events occurred after the neonicotinoid called imidacloprid was applied as a seed dressing to sunflower crops.
Varroa had already been present in France for some years - actually since 1982, yet beekeepers had not witnessed such collapses until after neonicotinoids were introduced on the market.