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Bt maize and bees

“Bees use maize pollen only when there are no alternatives.”

(18 July 2007) The Braunschweig administrative court has refused a fast-track appeal against the cultivation of genetically modified Bt maize. The environmental organisation Greenpeace and the Aktion Genklage alliance wanted the courts to rule in favour of two beekeepers that MON810 Bt maize growing in the vicinity of their beehives must not be allowed to flower. They claim that the maize poses a particularly unacceptable risk to honey bees. The indictment makes reference to a biosafety research project. In field experiments lasting several years, scientists at the universities of Jena and Halle had fed Bt maize pollen to bees. GMO Safety spoke to the project leader, Prof. Hans-Hinrich Kaatz.

Maize tassels with maize pollen

Appeal rejected: The Braunschweig administrative court rejected the appeal against the Federal Office of Consumer Protection and Food Safety (BVL) without looking into the question of any potential risk to the bees from Bt maize pollen. The court ruled that the BVL did not have the authority to refuse cultivation of the authorised MON810 Bt maize. The BVL is, it states, responsible only for authorisations. Measures relating to Bt maize that has already been sown come under the authority of the regional offices. Neither was the BVL under any obligation to order monitoring measures for the current 2007 growing season.

The background: In May the Federal Office of Consumer Protection and Food Safety (BVL) banned the sale of seed from genetically modified MON810 maize until such time as the producer, Monsanto, presents an up-to-date monitoring plan. Justification: There were new findings about the potential environmental risks. However, this did not affect the seed already distributed to farmers or sown. To prevent honey bees (Apis mellifera) being endangered by Bt maize pollen, Greenpeace and the Aktion Genklage alliance hope to ensure by means of an application for interim measures submitted to the Braunschweig administrative court that MON810 Bt maize planted on two plots of land close to bee colonies will either be ploughed under or harvested before it flowers, or that the pollen tassels will be cut off.

To prevent honey bees (Apis mellifera) being endangered by Bt maize pollen, Greenpeace and the Aktion Genklage alliance hope to ensure by means of an application for interim measures submitted to the Braunschweig administrative court that MON810 Bt maize planted on two plots of land close to bee colonies will either be ploughed under or harvested before it flowers, or that the pollen tassels will be cut off.

One result of the experiments is repeatedly brought up in the discussion surrounding the compatibility of Bt maize with bees: in the first year the bee colonies were coincidentally attacked by parasites (microsporidia). The colonies fed with Bt pollen appeared to be weakened much more by this attack than the other colonies. It has not been possible to investigate this effect further, since it has not been possible to raise microsporidia in large numbers for a deliberate infection of bee colonies.

When the experiment was repeated, the bees were treated with an antibiotic to prevent them being infected again. No further differences were found.

GMO Safety: According to Greenpeace, time is pressing because the main flowering time for the maize is mid- to late July. During this period they say maize is the main foraging crop for bees. Does maize have any significance for bees?

Hans-Hinrich Kaatz: Maize is certainly not a nectar plant and it is not attractive as a pollen plant. Bees use maize pollen only when there are no alternatives. At the time, we placed bee colonies on or directly adjacent to the maize fields. The proportion of maize pollen in the total pollen collected was extremely low: less than six per cent. This is because the bees also fly to neighbouring fallow land and border strips, where there is often more attractive pollen to be found. Remember, most pollen grains are as big as small tennis balls to a bee, while maize pollen grains are as large as medicine balls by comparison, which makes them harder for the bees to collect. However, there have also been other studies that have found up to 25 per cent maize pollen in the pollen collected.

GMO Safety: Your BMBF-funded project was cited – as it has often been in public debate – as proof of the harmfulness of the Bt toxin for bees. What quantities of Bt maize pollen were offered to the bee colonies in your project?

Hans-Hinrich Kaatz: We placed bee colonies in flight tents on a meadow with scattered fruit trees and offered them maize pollen or Bt maize pollen over the course of six weeks, which is longer than the normal maize flowering period, which lasts no more than two weeks. We did this in four consecutive years. In the first two years, the Bt maize pollen was enriched with ten times the concentration of Bt toxin. The bees were therefore exposed to Bt toxin to a far greater extent than under natural conditions.

GMO Safety: In the first year of your research, the bee colonies were coincidentally attacked by parasites, microsporidia. This attack led to a reduction in the number of bees and a reduction in brood rearing. In colonies fed on Bt pollen, this effect was much higher than in colonies that received conventional maize pollen. It is possible that microsporidia infection leads to a higher sensitivity to the Bt toxin. In the indictment it says that it is a known fact among bee experts that microsporidia occur in nearly every bee colony.

Hans-Hinrich Kaatz: Yes, it is common, no question about it. Microsporidia are spread as spores, but in most colonies there are no clinical signs, i.e. the colonies are not sick. If you dissect bee intestines, you find no microsporidia in the majority of bees. They occur primarily in very long-lived bees that are exposed to microsporidia for longer. Then there can be several reproduction cycles within the bees, so that we generally have a high incidence of microsporidia in the spring. This is well known. During the summer, i.e. during the time the maize flowers, microsporidia levels fall.

GMO Safety: How high do you think the proportion of pathogenic attack is?

Hans-Hinrich Kaatz: An attack is only pathological if it is serious. In our experiments we collected pollen, froze it and started with the experiments in the spring, so that we could conduct several series of trials successively over the summer. If we wait until August, until the maize pollen is available, the bee season is over, so the experiments need to begin earlier. We began at the end of May, when of course the level of Nosema infection (a type of microsporidia - Ed) in the colonies is automatically higher. In the spring these microsporidia are found in around fifty per cent of all bee colonies. During the maize flowering season in the summer, the level of infection of bee colonies with these microsporidia is less than ten per cent.

GMO Safety: Last year there was a study by scientists at the University of Wisconsin-Madison, who wrote that the toxic effect of Bt toxin on other non-target organisms depends on the activity of intestinal bacteria. When you repeated the experiment you treated the bees with antibiotics as a precaution. The indictment concludes from this that the trial results were therefore not sound.

Hans-Hinrich Kaatz: Yes, we treated the bees with an antibiotic in order to be absolutely certain that Nosema is not a factor. But this did not kill the bacteria. We used an antibiotic for microsporidia, i.e. eukaryotes.

GMO Safety: What is standard practice in beekeeping? Do beekeepers also use these special antibiotics against microsporidia?

Hans-Hinrich Kaatz: No. Because they target eukaryotes, they are also toxic to humans so are not used in Germany or in the rest of Europe. They are used to some extent in other parts of the world, but are in fact banned. In Germany, no traces of this antibiotic are allowed to be present in honey, otherwise the honey is unfit for sale. This means that you always need special authorisation for these kinds of experiments. Once again: The use of antibiotics in bee colonies to combat microsporidia is prohibited and is not in the interest of any beekeeper who produces natural honey as a high-quality food product.

GMO Safety: Do you see any need to repeat the experiments with healthy bees without antibiotics?

Hans-Hinrich Kaatz: I have done so. The repeat experiments with healthy bees without antibiotics produced the same results as those with antibiotics. Before the trial began, we checked carefully whether the bees were infected with Nosema. We dissect bee intestines and can then test how high the level of Nosema infection is. You can see the spores and judge whether the insects are healthy as regards microsporidia infection. Of course we only do that with samples. We take at least ten bees from a colony of around 30,000 bees and test them. This is the standard test used today.

Of course, I would also like to investigate the interactions in greater detail. Why was it that the colonies fed on Bt pollen were more sensitive to the microsporidia attack? What happened there?

GMO Safety: One last question: What is your general opinion about the risk to bees posed by Mon810 Bt maize?

Hans-Hinrich Kaatz: With the relatively small fields on which Bt maize is grown at the moment, I see no danger to the bees’ health. It could be different though for large-scale cultivation.

GMO Safety: Thank you for talking to us.