Alone in the maize field
The end of June, nine thirty in the morning at the edge of the field, as agreed. A vast field of maize, several trial tents, but no one to be seen, despite the fact that the maize stands no more than 1.30 metres high and you can easily see over it.
|
It soon becomes apparent, however, that even slight bumps and wrinkles in the field – one could hardly call them hills – are enough to obscure the view. A call to project leader Mr Leopold on the mobile. He is approaching the field margin but it will take five or ten minutes. In the 27-hectare field, trial plants are grown on 17.5 hectares and the rest is a cordon of non-trial plants. Today, as usual, Leopold is alone in the field. But even when colleagues are there too, he won’t necessarily see much of them. Even if you are just a few metres away from each other, you can hardly find one another without a mobile phone or walkie-talkie. Quite incredible, especially as the maize has not yet reached head height! And to prove the point, a short time later the tent we have just visited can no longer be seen, although it really cannot be more than fifteen metres away. There is not much point in shouting either, because the maize rustles loudly in the wind. The researchers have a red bucket for emergencies. This is placed on the nearest path between the plots to give them a better chance of guiding someone to them by mobile phone, if they are unable to reach the field margin on their own; a sprained ankle, for example, is all it takes. The presence of wild boar gives cause for concern, too. Tracks are regularly seen. The fear of encountering one doesn’t seem that absurd if you imagine being in the field at dusk or dawn. Since the university pool car cannot be ‘purloined’ for weeks at a time, Leopold is brought to the site and stays for a few days because it’s too far to drive every day. He lodges in a guesthouse in a nearby village. Then he makes the journey to the field either by bicycle or on foot. Today he is walking. So after a long day in the field, he has to walk four or five kilometres before he can have a shower and an evening meal. Counting, identifying and observing aphids Leopold is working on a project to examine the potential effects of genetic modification in maize on aphids and their specialised antagonists, e.g. parasitic wasps. First the extent of the infestation must be determined. Since there is are large numbers of aphids this year, Leopold has to spend three days a week in the field for a period of several weeks. The trial field is divided into plots growing two different Bt maize strains and, by way of comparison, the same strains without genetic modification – the so-called isogenic strains – along with several other conventional varieties. Each variant is repeated several times on different plots. Leopold has a map showing the location of the various plots and their respective crops. In addition there is a series of markers that enable one to relocate and study the same plants every time. Potential effects can be attributed to differences between the variants only if the same site and the same plants are used consistently.
|
|
The infestation is very high this year, which means that there is a lot of counting to be done. Not to mention identifying the different species. Aphid mummies are also collected and the parasitoids inside them are hatched in the laboratory and studied. Aphids are collected as well, because they often retreat into the soil once they have been parasitised. If only the mummies on the leaves were collected, one would obtain an incomplete picture. In the laboratory the collected aphids are placed on plants, at the base of which the soil has been sealed with plaster. This enables the aphids making their way down to the soil to be caught and examined for parasitisation. The tent trials also need attention. There are three types of insect-proof tent: one with transgenic maize, one with non-transgenic reference plants (isogenic strain) and one with a conventional variety commonly grown in Germany. The aim of the tents is specifically to study the influence of the maize variants on aphids and their antagonists using the example of the parasitic wasp Aphelinus abdominalis, in field conditions, but in the absence of other native antagonists. For this reason the tents were erected at the beginning of spring, when the maize plants were just five to ten centimetres high and before the arrival of beneficial predators. The aim was that the maize plants would be colonised by aphids released in the tents in mid June. Although these are aphids which originate in maize fields and it is a very good year for them, this is proving difficult. More aphids may have to be released in the tents. Then the parasitic wasps. It takes about eight days for the aphids to become mummified. About ten days later, a new generation of parasitic wasps hatch from the mummies. Last year’s chaff Last year’s chaff lies all around. The plant remains were not ploughed in last year, but left in the field. The thinking behind this is that European corn borers, to which the transgenic maize is resistant, like to overwinter in this chaff. A heavy infestation by the European corn borer is hoped for, because differences between the maize variants are then more likely. According to Leopold, this looks like being a good year for the European corn borer; he has seen several of the little butterflies flying around in the evenings. After a good hour in the maize field, the visit is over. Leopold still has a long day ahead of him – counting, collecting and identifying aphids. During the afternoon, while this article is being written, it starts to rain. And what did Leopold leave behind at home in Göttingen this week? – His wet weather gear. |
More from GMO Safety
![[jump to top]](/images/icons/icon_gotop_9x9.gif){kind=icon}