New research has suggested that reduced plant diversity may be a cause for the decline of honeybees that has been seen in many countries in recent years.

Bees that have been fed pollen from a range of plants showed signs of having a healthier immune system than those eating pollen from a single type.

Those fed with a mix of five different pollens had higher levels of glucose oxidase compared to bees fed with pollen from one single type of flower, even if that single flower had a higher protein content. Bees make glucose oxidase to preserve honey and food for larvae against infestation by microbes - which protects the hive against disease.

Previous research has showed that the diversity of bees and other insects was falling alongside the diversity of plants they fed on and pollinated. So the large areas of monoculture food production have caused a fairly major change in the variety of species that pollinating insects can forage for.

Other new research, suggests that bee numbers are falling twice as fast in the UK as in the rest of Europe - with the commercial value of bees' pollination estimated at £200m per year in the UK their decline could have significant effects. There is an increased demand for the UK to produce its own food - but many fruits and vegetables rely on pollinators such as bees.

The French government has just announced a project to sow nectar-bearing flowers by roadsides in an attempt to stem honey bee decline.

Experts have looked at causes for their decline from everything from climate change, to pesticides, the varroa mite or a mysterious ailment known as colony collapse disorder or CCD. This new research is likely to be another piece in the jigsaw.