Two pesticides commonly used by farmers may be killing off bees.
A pair of studies published in the influential Science journal investigated two types of neonicotinoid pesticides and found that even safe doses can cause hives to collapse.
Otago University director of genetics Associate Professor Peter Dearden says there has been anecdotal evidence on that for years.
However, he says the studies provide the first hard evidence that while the pesticides don't kill the bees immediately, they have harmful longer term effects.
The studies found the pesticides cause foraging bees to become disorientated, losing their way back to the hive.
Professor Dearden says more research is needed and it is important not to rush into a complete ban of the pesticides.