By Richard Gray, The Telegraph
The work is being pioneered by biologists at Rothamsted Research, the government funded crop research site in Hertfordshire, and scientists in Germany.
Using lightweight radar transponders less than an inch long that are glued onto the backs of honey bees, the researchers have been able to accurately track the flight paths taken by individual honey bees.
However the researchers have found that the insects, which have suffered dramatic declines over the past 25 years, become disorientated and have trouble navigating when exposed to controversial pesticides called neonicotinoids.
Tests show bees that have eaten syrup contaminated with the pesticides are unable to use their memory of landmarks in their surroundings to find their way back to their hives, flying in random circles rather than straight lines.
Professor Randolf Menzel, an insect neurobiologist at the Free University in Berlin, who has led the work, has found that bees use two types of memory to navigate – a kind of automatic pilot or “vector memory” and their memory of the landscape, which they form during earlier foraging flights.
He said: “We tested around 200 bees both control bees and pesticide treated bees. We find the control bees are just fantastic – they use their landscape and their vector memory and they do fine.
“The treated bees, depending on the doses of the substance, are more confused. They usually do quite well when they fly along the vector but when they need to use their landscape memory, then they become lost.
“It seems to me that neonicotinoids are endangering honey bees.”
He fears that as bees exposed to the pesticides are less able to navigate they struggle to find food and bring it back to the hive, leaving the insects weakened and less able to deal with disease and poor weather.
The findings, which will appear this week in a special episode of Horizon on BBC One, appear to support the claims of environmental groups who claim that widespread pesticide use on crops is one of the causes of honey bee decline.
In the past 25 years numbers of the insects have more than halved and it has raised fears that their populations could collapse. Bees are one of the main insects responsible for pollinating major food crops such as fruits and oil seed rape.
Earlier this year the European Union voted to ban the use of neonicotinoids over fears they are harming bees, but the UK government did not support the ban, saying more research was needed.
Critics also say the doses of the pesticides used in tests like those by Professor Menzel are far higher than those that bees would be exposed to in the natural environment.
Scientists at Rothamsted Research are also using the radar equipment to study how another major threat to bee health effects their ability to navigate.
Using the tiny transponders, which are glued onto the backs of bees that have been captured, the Dr Stephan Wolf and Dr Jason Lim are studying the flight paths of bees infected with a virus transmitted by the varroa mite.
Dr Wolf said: “The radar allows us to do something that would have been impossible in the past. It lets us not only see if and when a bee returns to the hive but also lets us see where the bees go and how it makes that flight.
“The orientation flights of bees can range over several hundred metres and they can loop for up to an hour, so there is no way you can follow that by eye. We are now able to dig a lot deeper into how disease status might impact on their flight.”
* Horizon: What’s Killing Our Bees? will be broadcast on BBC TWO on Friday 2 July