Hamburg, Germany - Honey bees are more effective than insecticides in keeping harmful pests such as caterpillars away from your prize flowers, according to a team of German scientists.

Like winged watchdogs, honey bees chase away intruders who threaten to devour their beloved pollination buds. Not only do they chase away humans, but also other bugs.

Caterpillars are particularly sensitive to bees since the buzzing of the insects' wings irritates the sensitive hairs on their bodies.

Unable to tell apart a harmless bee and a predatory wasp, the leaf-munching larvae are frightened away, according to researcher Dr Jurgen Tautz, from the University of Wurzburg in Germany.

"These sensory hairs are not fine-tuned. Therefore, caterpillars cannot distinguish between hunting wasps and harmless bees," Tautz said.

The German scientists found that caterpillars stopped moving or dropped off the plant they were feeding on, if an "unidentified flying object" approached generating air vibrations of the right frequency.

Constant stress from buzzing bees foraging for nectar caused caterpillars to feed a lot less, said Tautz.

The German scientists conducted an experiment in which bell pepper plants were kept in tents with either bees and caterpillars or caterpillars alone.

Plants surrounded by buzzing bees suffered between 60 per cent and almost 70 per cent less damage to their leaves than those which were unprotected.

"Our findings indicate for the first time that visiting honeybees provide plants with a totally unexpected advantage," the German researchers reported in the journal Current Biology.

"They not only transport pollen from flower to flower, but in addition also reduce plant destruction by herbivores."

The findings highlighted the way apparently unrelated members of food webs interacted in nature, said Dr Tautz.

He thought they may have a practical application in sustainable agriculture.

His team now plans to investigate whether combining crops with flowers that attract bees can improve yields in areas plagued by leaf-eating pests.

"Our finding may be the start of a totally new biological control method," said Tautz. (dpa)