Bt maize: effective against maize pests
Bt maize is genetically modified maize that produces an insecticide – Bt protein. The gene responsible for this trait transferred to maize comes from a naturally occurring bacterium in soil called Bacillus thuringiensis. Hence, the name Bt maize.
The insecticide effect of this bacterium has long been known and it is used as a plant protectant. Bt preparations are most frequently used today in organic farming as a biological pesticide. The Bt protein has the advantage that it can be used for the highly targeted control of certain pests. Furthermore, it is absolutely harmless to humans. When first produced, the Bt protein is in a non-toxic form. It is only in the gut of certain chewing insects that it then becomes toxic.
The European corn borer: a major pest
There are many different Bt proteins, each specifically effective against a certain group of insects. The most prevalent types of Bt maize grown worldwide are those that are resistant to the European corn borer. Approved for cultivation in Europe, but banned in Germany since spring 2009, Bt maize MON810 produces a Bt protein that is specifically effective against this pest. The small grey-brown moth is a major maize pest, causing extensive damage. In early spring the young larvae bore into the maize plants chewing their way through the stem during the growing season. The pest has spread throughout all maize-growing areas of south and south-east Europe. In Germany it has steadily advanced from the south to the north having now reached the Baltic coast. In areas of heavy infestation, Bt maize can be of significant benefit since it is highly targeted and effective against this pest. In comparison with chemical pesticides, Bt maize is more protective of the biodiversity in the maize field.
Fewer fungal toxins
A further advantage of Bt maize is reduced contamination by fungal toxins (mycotoxins). Maize plants weakened and damaged by the chewed-out hollows of the corn borer larvae are susceptible to fungal infections. Some of those fungi, such as Fusarium, produce mycotoxins that contaminate maize-derived food and fodder. Several studies have confirmed that Bt maize plants generally show lower levels of mycotoxins than conventional maize plants.
Bt maize plots in the Plant Science Garden
Various maize varieties carrying a Bt gene making them resistant to the European corn borer or Western corn rootworm can be seen in the Plant Science Garden. As comparison, their respective non-GM cultivars bearing the same traits are grown on neighbouring plots.
Some Bt maize varieties produce a variant of the Bt protein aimed against the European corn borer; another targets the Western corn rootworm, a new pest that is already prevalent throughout southern and eastern Europe, having caused extensive damage there. In the meantime, the Western corn rootworm has also shown up in Bavaria and Baden-Württemberg in Germany.
Date: 2011
