Aug 19, 2010

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Pest spreads to other parts of Germany

Western corn rootworm found in North Rhine-Westphalia for the first time

On 17 August, the North Rhine-Westphalian Ministry of Agriculture announced that eight Western corn rootworm specimens had been found in Cologne. Until then, the beetle had been found only in Bavaria and Baden-Württemberg. It is one of the worst maize pests worldwide and is classed as a quarantine pest in the EU.

The Western corn rootworm Diabrotica virgifera, a maize pest feared by farmers all over the world, is spreading to other parts of Germany.

The larvae of the Western corn rootworm feed on maize roots.

If the maize roots are damaged by the larvae, the plants become unstable and fall over.

Around 20 million hectares of maize-growing land is infested by the Western corn rootworm (Diabrotica virgifera) worldwide, of which around 13.5 million hectares are in the USA. It mainly damages the roots of maize plants. A severe infestation can lead to up to 80 per cent of the plant stems snapping in half. The loss to farmers is immense. In the USA the cost of the damage caused by Diabrotica and the cost of controlling the pest add up to around a billion US dollars each year.

By natural means, i.e. flying, the Western corn rootworm can travel up to 100 km a year. However, long-distance transportation has repeatedly led to isolated instances of accidental introduction that have played an important role in its spread. For instance, at the end of the 1980s, the pest reached Europe – travelling by plane from North America to former Yugoslavia. This kind of importation is really the only explanation for the sudden appearance of the beetle in North Rhine-Westphalia. The field in question is close to Cologne/Bonn Airport.

But the natural spread of the Western corn rootworm in Germany is also continuing. As the Ministry of Agriculture of Baden-Württemberg announced on 18 August, around 30 specimens of Diabrotica were caught in 2010 in the rural district of Breisgau-Hochschwarzwald, which was previously free from infestation.

EU-wide quarantine measures have been imposed to control the Western corn rootworm. According to the Ministry of Agriculture of North Rhine-Westphalia, these measures were introduced in Cologne the moment the beetles were found. A ‘focus zone’ with a radius of one kilometre was set up around the affected field, with a safety zone covering a five kilometre radius around that. Inside the focus zone, the pest is controlled with pesticides and no more maize can be grown for the time being. In the safety zone, crop rotation is prescribed, i.e. maize can be grown only every other year.

Another pest control strategy involves planting genetically modified maize varieties that produce a Bt protein, particularly in the plant roots, which targets the Western corn rootworm. In the USA these kinds of maize have been grown for several years. Applications for their approval have been filed in Europe, but as yet there is no sign of them being approved. From 2005 to 2008, a joint research project funded by the Federal Ministry of Education and Research (BMBF) studied whether cultivation of Diabrotica-resistant Bt maize could have harmful effects on the environment and on biodiversity. From 2008 to 2011, follow-up projects are studying a maize variety that produces several Bt proteins, one of which targets the Western corn rootworm.