Pollen from genetically modified Bt-corn - the transgenic plant that some believe poses a threat to butterflies - does no harm to honey bees.
New research has shown the Bt toxin, produced by commercially grown GM crops in the United States to ward off a major agricultural pest, has practically no impact on the "friendly" and commercially important insect.
However, the tests carried out by scientists at the Horticulture and Food Research Institute of New Zealand suggest the products of some other pest-resistant GM plants may disrupt the lifecycle of bees.
The work, which will be unveiled at the International Bee Research Association conference in Thailand next week, forms part of a major programme of experiments to assess the effects of GM-crops on non-
targeted insects.
Louise Malone, a member of the New Zealand team, said: "The impacts of transgenic plants on bees will depend on the nature of the gene introduced into the plant and on the bee's level of exposure to its protein product."
Research published last year by Cornell
University showed that monarch butterflies were threatened by pollen from Bt-corn, which had been engineered to carry a bacterial gene that produces Bt, a substance poisonous to the
European corn borer.
However, the conclusions drawn by the Cornell team's conclusions are still hotly disputed as many scientists felt the study did not involve realistic doses of the pollen.
The New Zealand studies involved feeding bees with proteins that pest-
resistant transgenes produce - Bt and several protease inhibitors also being investigated for GM-crops - the theory being that the bee could ingest the gene product if it is expressed in the pollen, nectar or sap of the plant.
Experiments found that those fed high concentrations of the protease inhibitor aprotinin, the Kunitz soybean trypsin inhibitor and two inhibitors from potatoes, had a poor survival rate.
With Bt, however, the results were negative,and only an extremely high dose of a Bt-based pesticide, Dipel, had any effect.
In another series of tests, adult bees were taken from their hives, tagged and kept in cages for seven days, during which time they were fed food dosed with either aprotinin, Bt or without any additive.
They were then returned, and the progress of those that were subsequently accepted back into the hive were monitored.
"Sufficient bees survived for us to make enough observations to show that the Bt-fed bees did not differ significantly from control bees in the timing of their first flight, the period during which flights took place or in estimated longevity," said Dr Malone.
Those that had ingested aprotinin began to fly and died three days sooner than the other tagged bees, possibly because they did not properly form a gland needed to pursue larval feeding duties and hence took to foraging for pollen and nectar earlier than they might otherwise have done.